Understanding How the File System State Is Recorded

The fsck command uses a state flag, which is stored in the superblock, to record the condition of the file system. This flag is used by the fsck command to determine whether or not a file system needs to be checked for consistency. The flag is used by the /etc/bcheckrc script during booting and by the fsck command when run from a command line using the -m option. If you ignore the result from the -m option to fsck, all file systems can be checked regardless of the setting of the state flag.

The possible state flag values are described in Table 39-1.

Table 39-1

State Flag Value	Description
FSCLEAN	If the file system was unmounted properly, the state flag is set to FSCLEAN. Any file system with an FSCLEAN state flag is not checked when the system is booted.
FSSTABLE	The file system is (or was) mounted but has not changed since the last checkpoint (sync or fsflush) which normally occurs every 30 seconds. For example, the kernel periodically checks if a file system is idle and, if so, flushes the information in the superblock back to the disk and marks it FSSTABLE. If the system crashes, the file system structure is stable, but users may lose a small amount of data. File systems that are marked FSSTABLE can skip the checking before mounting. The mount(2) system call will not mount a file system for read/write if the file system state is not FSCLEAN or FSSTABLE.
FSACTIVE	When a file system is mounted and then modified, the state flag is set to FSACTIVE. The file system may contain inconsistencies. A file system will be marked as FSACTIVE before any modified metadata is written to the disk. When a file system is unmounted gracefully, the state flag is set to FSCLEAN. A file system with the FSACTIVE flag must be checked by fsck because it may be inconsistent.
FSBAD	If the root (/) file system is mounted when its state is not FSCLEAN or FSSTABLE, the state flag is set to FSBAD. The kernel will not change this file system state to FSCLEAN or FSSTABLE. If a root (/) file system is flagged FSBAD as part of the boot process, it will be mounted read-only. You can run fsck on the raw root device. Then remount the root (/) file system as read/write.

Table 39-2 shows when the state flag is modified.

Table 39-2

Before fsck	After fsck
Initial State	No Errors	New State All Errors Corrected	Uncorrected Errors
unknown	stable	stable	unknown
active	stable	stable	active
stable	stable	stable	active
clean	clean	stable	active
bad	stable	stable	bad

What fsck Checks and Tries to Repair

This section describes what happens in the normal operation of a file system, what can go wrong, what problems fsck (the checking and repair utility) looks for, and how it corrects the inconsistencies it finds.

Why Inconsistencies May Occur

Every working day hundreds of files may be created, modified, and removed. Each time a file is modified, the operating system performs a series of file system updates. These updates, when written to the disk reliably, yield a consistent file system.

When a user program does an operation to change the file system, such as a write, the data to be written is first copied into an internal in-core buffer in the kernel. Normally, the disk update is handled asynchronously; the user process is allowed to proceed even though the data write may not happen until long after the write system call has returned. Thus at any given time, the file system, as it resides on the disk, lags behind the state of the file system represented by the in-core information.

The disk information is updated to reflect the in-core information when the buffer is required for another use or when the kernel automatically runs the fsflush daemon (at 30-second intervals). If the system is halted without writing out the in-core information, the file system on the disk will be in an inconsistent state.

A file system can develop inconsistencies in several ways. The most common causes are operator error and hardware failures.

Problems may result from an unclean halt, if a system is shut down improperly, or when a mounted file system is taken offline improperly. To prevent unclean halts, the current state of the file systems must be written to disk (that is, "synchronized") before halting the CPU, physically taking a disk pack out of a drive, or taking a disk offline.

Inconsistencies can also result from defective hardware. Blocks can become damaged on a disk drive at any time, or a disk controller can stop functioning correctly.

The UFS Components That Are Checked for Consistency

This section describes the kinds of consistency checks the fsck applies to these UFS file system components: superblock, cylinder group blocks, inodes, indirect blocks, and data blocks.

Superblock

The superblock stores summary information, which is the most commonly corrupted item in a UFS file system. Each change to the file system inodes or data blocks also modifies the superblock. If the CPU is halted and the last command is not a sync command, the superblock will almost certainly be corrupted.

The superblock is checked for inconsistencies in:

• File system size
• Number of inodes
• Free-block count
• Free-inode count

File System and Inode List Size The file system size must be larger than the number of blocks used by the superblock and the number of blocks used by the list of inodes. The number of inodes must be less than the maximum number allowed for the file system. The file system size and layout information are the most critical pieces of information for fsck. Although there is no way to actually check these sizes, because they are statically determined when the file system is created, fsck

can check that the sizes are within reasonable bounds. All other file system checks require that these sizes be correct. If fsck detects corruption in the static parameters of the primary superblock, it requests the operator to specify the location of an alternate superblock.

Free Blocks Free blocks are stored in the cylinder group block maps. fsck checks that all the blocks marked as free are not claimed by any files. When all the blocks have been accounted for, fsck checks to see if the number of free blocks plus the number of blocks claimed by the inodes equal the total number of blocks in the file system. If anything is wrong with the block allocation maps, fsck rebuilds them, leaving out blocks already allocated.

The summary information in the superblock contains a count of the total number of free blocks within the file system. The fsck program compares this count to the number of free blocks it finds within the file system. If the counts do not agree, fsck replaces the count in the superblock with the actual free-block count.

Free Inodes The summary information in the superblock contains a count of the free inodes within the file system. The fsck program compares this count to the number of free inodes it finds within the file system. If the counts do not agree, fsck replaces the count in the superblock with the actual free inode count.

Inodes

The list of inodes is checked sequentially starting with inode 2 (inode 0 and inode 1 are reserved). Each inode is checked for inconsistencies in:

• Format and type
• Link count
• Duplicate block
• Bad block numbers
• Inode size

Format and Type of Inodes Each inode contains a mode word, which describes the type and state of the inode. Inodes may be one of six types:

• Regular
• Directory
• Block special
• Character special
• FIFO (named-pipe)
• Symbolic link

Inodes may be in one of three states:

• Allocated
• Unallocated
• Partially allocated

When the file system is created, a fixed number of inodes are set aside, but they are not allocated until they are needed. An allocated inode is one that points to a file. An unallocated inode does not point to a file and, therefore, should be empty. The partially allocated state means that the inode is incorrectly formatted. An inode can get into this state if, for example, bad data is written into the inode list because of a hardware failure. The only corrective action fsck can take is to clear the inode.

Link Count Each inode contains a count of the number of directory entries linked to it. The fsck program verifies the link count of each inode by examining the entire directory structure, starting from the root directory, and calculating an actual link count for each inode.

Discrepancies between the link count stored in the inode and the actual link count as determined by fsck may be of three types:

• The stored count is not 0 and the actual count is 0.

  This condition can occur if no directory entry exists for the inode. In this case, fsck puts the disconnected file in the lost+found directory.

• The stored count is not 0 and the actual count is not 0, but the counts are unequal.

This condition can occur if a directory entry has been added or removed but the inode has not been updated. In this case, fsck replaces the stored link count with the actual link count.

• The stored count is 0 and the actual count is not 0.

  In this case fsck changes the link count of the inode to the actual count.

Duplicate Blocks Each inode contains a list, or pointers to lists (indirect blocks), of all the blocks claimed by the inode. Because indirect blocks are owned by an inode, inconsistencies in indirect blocks directly affect the inode that owns the indirect block.

The fsck program compares each block number claimed by an inode to a list of allocated blocks. If another inode already claims a block number, the block number is put on a list of duplicate blocks. Otherwise, the list of allocated blocks is updated to include the block number.

If there are any duplicate blocks, fsck makes a second pass of the inode list to find the other inode that claims each duplicate block. (A large number of duplicate blocks in an inode may be caused by an indirect block not being written to the file system.) It is not possible to determine with certainty which inode is in error. The fsck program prompts you to choose which inode should be kept and which should be cleared.

Bad Block Numbers The fsck program checks each block number claimed by an inode to see that its value is higher than that of the first data block and lower than that of the last data block in the file system. If the block number is outside this range, it is considered a bad block number.

Bad block numbers in an inode may be caused by an indirect block not being written to the file system. The fsck program prompts you to clear the inode.

Inode Size Each inode contains a count of the number of data blocks that it references. The number of actual data blocks is the sum of the allocated data blocks and the indirect blocks. fsck computes the number of data blocks and compares that block count against the number of blocks the inode claims. If an inode contains an incorrect count, fsck prompts you to fix it.

Each inode contains a 64-bit size field. This field shows the number of characters (data bytes) in the file associated with the inode. A rough check of the consistency of the size field of an inode is done by using the number of characters shown in the size field to calculate how many blocks should be associated with the inode, and then comparing that to the actual number of blocks claimed by the inode.

Indirect Blocks

Indirect blocks are owned by an inode. Therefore, inconsistencies in an indirect block affect the inode that owns it. Inconsistencies that can be checked are:

• Blocks already claimed by another inode
• Block numbers outside the range of the file system

The consistency checks are also performed for indirect blocks.

Data Blocks

An inode can directly or indirectly reference three kinds of data blocks. All referenced blocks must be of the same kind. The three types of data blocks are:

• Plain data blocks
• Symbolic-link data blocks
• Directory data blocks

Plain data blocks contain the information stored in a file. Symbolic-link data blocks contain the path name stored in a symbolic link. Directory data blocks contain directory entries. fsck can check the validity only of directory data blocks.

Directories are distinguished from regular files by an entry in the mode field of the inode. Data blocks associated with a directory contain the directory entries. Directory data blocks are checked for inconsistencies involving:

• Directory inode numbers pointing to unallocated inodes
• Directory inode numbers greater than the number of inodes in the file system
• Incorrect directory inode numbers for "." and ".." directories
• Directories disconnected from the file system

Directory Unallocated If the inode number in a directory data block points to an unallocated inode, fsck removes the directory entry. This condition can occur if the data blocks containing the directory entries are modified and written out but the inode does not get written out. This condition can occur if the CPU is halted without warning.

Bad Inode Number If a directory entry inode number points beyond the end of the inode list, fsck removes the directory entry. This condition can occur when bad data is written into a directory data block.

Incorrect "." and ".." Entries The directory inode number entry for "." must be the first entry in the directory data block. It must reference itself; that is, its value must be equal to the inode number for the directory data block.

The directory inode number entry for ".." must be the second entry in the directory data block. Its value must be equal to the inode number of the parent directory (or the inode number of itself if the directory is the root directory).

If the directory inode numbers for "." and ".." are incorrect, fsck replaces them with the correct values. If there are multiple hard links to a directory, the first one found is considered the real parent to which ".." should point. In this case, fsck recommends you have it delete the other names.

Disconnected Directories The fsck program checks the general connectivity of the file system. If a directory is found that is not linked to the file system, fsck links the directory to the lost+found directory of the file system. (This condition can occur when inodes are written to the file system but the corresponding directory data blocks are not.)

Regular Data Blocks

Data blocks associated with a regular file hold the contents of the file. fsck does not attempt to check the validity of the contents of a regular file's data blocks.

Error Messages

Normally, fsck is run non-interactively to preen the file systems after an abrupt system halt in which the latest file system changes were not written to disk. Preening automatically fixes any basic file system inconsistencies and does not try to repair more serious errors. While preening a file system, fsck fixes the inconsistencies it expects from such an abrupt halt. For more serious conditions, the command reports the error and terminates.

When you run fsck interactively, fsck reports each inconsistency found and fixes innocuous errors. However, for more serious errors, the command reports the inconsistency and prompts you to choose a response. When you run fsck using the -y or -n options, your response is predefined as yes or no to the default response suggested by fsck for each error condition.

Some corrective actions will result in some loss of data. The amount and severity of data loss may be determined from the fsck diagnostic output.

fsck is a multipass file system check program. Each pass invokes a different phase of the fsck program with different sets of messages. After initialization, fsck performs successive passes over each file system, checking blocks and sizes, path names, connectivity, reference counts, and the map of free blocks (possibly rebuilding it). It also performs some cleanup.

The phases (passes) performed by the UFS version of fsck are:

• Initialization
• Phase 1 - Check blocks and sizes

• Phase 2 - Check path names
• Phase 3 - Check connectivity
• Phase 4 - Check reference counts
• Phase 5 - Check cylinder groups

The next sections describe the error conditions that may be detected in each phase, the messages and prompts that result, and possible responses you can make.

Messages that may appear in more than one phase are described in "General fsck Error Messages" on page 644. Otherwise, messages are organized alphabetically by the phases in which they occur.

Many of the messages include the abbreviations shown in Table 39-3:

Table 39-3

Abbreviation	Meaning
BLK	Block number
DUP	Duplicate block number
DIR	Directory name
CG	Cylinder group
MTIME	Time file was last modified
UNREF	Unreferenced

Many of the messages also include variable fields, such as inode numbers, which are represented in this book by an italicized term, such as inode-number. For example, this screen message:

    INCORRECT BLOCK COUNT I=2529

is shown as:

INCORRECT BLOCK COUNT I=inode-number

General fsck Error Messages

The error messages in this section may be displayed in any phase after initialization. Although they offer the option to continue, it is generally best to regard them as fatal. They reflect a serious system failure and should be

handled immediately. When confronted with such a message, terminate the program by entering no. If you cannot determine what caused the problem, contact your local service provider or another qualified person.

CANNOT SEEK: BLK block-number (CONTINUE)

A request to move to a specified block number block-number in the file system failed. This message indicates a serious problem, probably a hardware failure.

If you want to continue the file system check, do a second run of fsck to recheck the file system. If the block was part of the virtual memory buffer cache, fsck will terminate with a fatal I/O error message.

CANNOT READ: BLK block-number (CONTINUE)

A request to read a specified block number in the file system failed. The message indicates a serious problem, probably a hardware failure. If you want to continue the file system check, fsck will retry the read and display a list of sector numbers that could not be read.

If fsck tries to write back one of the blocks on which the read failed it displays this message:

WRITING ZERO'ED BLOCK sector-numbers TO DISK

If the disk is experiencing hardware problems, the problem will persist. Run fsck again to recheck the file system. If the block was part of the virtual memory buffer cache, fsck terminates and displays this error message:

Fatal I/O error

CANNOT WRITE: BLK block-number (CONTINUE)

A request to write a specified block number block-number in the file system failed. The disk may be write-protected. Check the write-protect lock on the drive. If that is not the problem, contact your local service provider or another qualified person. If you continue the file system check, the write operation will be retried. Sectors that could not be written are shown with this message:

THE FOLLOWING SECTORS COULD NOT BE WRITTEN: sector-numbers

where sector-numbers indicates the sectors that could not be written. If the disk has hardware problems, the problem will persist. This error condition prevents a complete check of the file system. Run fsck a second time to recheck this file system. If the block was part of the virtual memory buffer cache, fsck terminates and displays this error message:

Fatal I/O error

Initialization Phase fsck Messages

In the initialization phase, command-line syntax is checked. Before the file system check can be performed, fsck sets up tables and opens files.

The messages in this section relate to error conditions resulting from command-line options, memory requests, the opening of files, the status of files, file system size checks, and the creation of the scratch file. All such initialization errors terminate fsck when it is preening the file system.

bad inode number inode-number to ginode

Reason Error Occurred	How to Solve the Problem
An internal error occurred because of a nonexistent inode	Contact your local service provider or another qualified
inode-number. fsck exits.	person.
cannot alloc size-of-block map bytes for blockmap
Reason Error Occurred	How to Solve the Problem
Request for memory for its internal tables failed. fsck	Killing other processes may solve the problem. If not,
terminates. This message indicates a serious system	contact your local service provider or another qualified
failure that should be handled immediately. This	person.

condition may occur if other processes are using a very large amount of system resources.

Can't open checklist file: filename

Reason Error Occurred	How to Solve the Problem
The file system checklist file filename (usually	Check if the file exists and if its access modes permit read
/etc/vfstab) cannot be opened for reading. fsck	access.

terminates.

Can't open filename

Reason Error Occurred	How to Solve the Problem
fsck cannot open file system filename. When running	Check to see if read and write access to the raw device
interactively, fsck ignores this file system and continues	file for the file system is permitted.

checking the next file system given.

Can't stat root

Reason Error Occurred	How to Solve the Problem
fsck request for statistics about the root directory failed.	This message indicates a serious system failure. Contact
fsck terminates.	your local service provider or another qualified person.

Can't stat filename Can't make sense out of name filename

Reason Error Occurred	How to Solve the Problem
fsck request for statistics about the file system filename	Check if the file system exists and check its access modes.

failed. When running interactively, fsck ignores this file system and continues checking the next file system given.

filename: (NO WRITE)

Reason Error Occurred	How to Solve the Problem
Either the -n option was specified or fsck could not	If -n was not specified, check the type of the file
open the file system filename for writing. When fsck is	specified. It may be the name of a regular file.

running in no-write mode, all diagnostic messages are displayed, but fsck does not attempt to fix anything.

IMPOSSIBLE MINFREE=percent IN SUPERBLOCK (SET TO DEFAULT)

Reason Error Occurred	How to Solve the Problem
The superblock minimum space percentage is greater	To set the minfree parameter to the default 10 percent,
than 99 percent or less than 0 percent.	type y at the default prompt. To ignore the error condition, type n at the default prompt.

INTERNAL INCONSISTENCY: message

Reason Error Occurred	How to Solve the Problem
fsck has had an internal error, whose message is	If one of the following messages are displayed, contact
message.	your local service provider or another qualified person:

MAGIC NUMBER WRONG
NCG OUT OF RANGE
CPG OUT OF RANGE
NCYL DOES NOT JIBE WITH NCG*CPG
SIZE PREPOSTEROUSLY LARGE
TRASHED VALUES IN SUPER BLOCK

This message may be followed by an error in the following example:

filename: BAD SUPER BLOCK: block-number USE AN ALTERNATE SUPER-BLOCK TO SUPPLY NEEDED INFORMATION; e.g., fsck[-f ufs] -o b=# [special ...] where # is the alternate superblock. See fsck_ufs(1M)

Reason Error Occurred	How to Solve the Problem
The superblock has been corrupted.	Use an alternative superblock to supply needed information. Specifying block 32 is a good first choice. You can locate an alternative copy of the superblock by running the newfs -N command on the slice. Be sure to specify the -N option; otherwise, newfs overwrites the existing file system.

UNDEFINED OPTIMIZATION IN SUPERBLOCK (SET TO DEFAULT)

Reason Error Occurred	How to Solve the Problem
The superblock optimization parameter is neither	To minimize the time to perform operations on the file
OPT_TIME nor OPT_SPACE.	system, type y at the SET TO DEFAULT prompt. To ignore this error condition, type n.

Phase 1: Check Blocks and Sizes Messages

This phase checks the inode list. It reports error conditions encountered while:

• Checking inode types
• Setting up the zero-link-count table
• Examining inode block numbers for bad or duplicate blocks
• Checking inode size
• Checking inode format

All errors in this phase except INCORRECT BLOCK COUNT, PARTIALLY TRUNCATED INODE, PARTIALLY ALLOCATED INODE, and UNKNOWN FILE TYPE terminate fsck when it is preening a file system.

The other possible error messages displayed in this phase are referenced below.

• BAD STATE state-number TO BLKERR
• block-number DUP I=inode-number
• EXCESSIVE BAD BLOCKS I=inode-number (CONTINUE)
• EXCESSIVE DUP BLKS I=inode-number (CONTINUE)
• INCORRECT BLOCK COUNT I=inode-number (number-of-BAD-DUP-or-missing-blocks should be number-of-blocks-in-filesystem) (CORRECT)
• LINK COUNT TABLE OVERFLOW (CONTINUE)
• PARTIALLY ALLOCATED INODE I=inode-number (CLEAR)
• PARTIALLY TRUNCATED INODE I=inode-number (SALVAGE)
• UNKNOWN FILE TYPE I=inode-number (CLEAR)

These messages (in alphabetical order) may occur in phase 1:

block-number BAD I=inode-number

Reason Error Occurred	How to Solve the Problem
Inode inode-number contains a block number block-number	N/A

with a number lower than the number of the first data block in the file system or greater than the number of the last block in the file system. This error condition may generate the EXCESSIVE BAD BLKS error message in phase 1 if inode inode-number has too many block numbers outside the file system range. This error condition generates the BAD/DUP error message in phases 2 and 4.

BAD MODE: MAKE IT A FILE?

Reason Error Occurred	How to Solve the Problem
The status of a given inode is set to all 1s, indicating file	Type y to reinitialize the inode to a reasonable value.

system damage. This message does not indicate physical disk damage, unless it is displayed repeatedly after fsck -y has been run.

BAD STATE state-number TO BLKERR

Reason Error Occurred	How to Solve the Problem
An internal error has scrambled the fsck state map so	Contact your local service provider or another qualified
that it shows the impossible value state-number. fsck	person.

exits immediately.

block-number DUP I=inode-number

Reason Error Occurred	How to Solve the Problem
Inode inode-number contains a block number block-number,	N/A

which is already claimed by the same or another inode. This error condition may generate the EXCESSIVE DUP BLKS error message in phase 1 if inode inode-number has too many block numbers claimed by the same or another inode. This error condition invokes phase 1B and generates the BAD/DUP error messages in phases 2 and 4.

DUP TABLE OVERFLOW (CONTINUE)

Reason Error Occurred	How to Solve the Problem
There is no more room in an internal table in fsck	To continue the program, type y at the CONTINUE
containing duplicate block numbers. If the -o p option is	prompt. When this error occurs, a complete check of the
specified, the program terminates.	file system is not possible. If another duplicate block is found, this error condition repeats. Increase the amount of virtual memory available (by killing some processes, increasing swap space) and run fsck again to recheck the file system.

To terminate the program, type n.

EXCESSIVE BAD BLOCKS I=inode-number (CONTINUE)

Reason Error Occurred	How to Solve the Problem
Too many (usually more than 10) blocks have a number	To continue the program, type y at the CONTINUE
lower than the number of the first data block in the file	prompt. When this error occurs, a complete check of the
system or greater than the number of the last block in the	file system is not possible. You should run fsck again to
file system associated with inode inode-number. If the	recheck the file system.

-o p (preen) option is specified, the program terminates. To terminate the program, type n.

EXCESSIVE DUP BLKS I=inode-number (CONTINUE)

Reason Error Occurred	How to Solve the Problem
Too many (usually more than 10) blocks are claimed by	To continue the program, type y at the CONTINUE
the same or another inode or by a free-list. If the -o p	prompt. When this error occurs, a complete check of the
option is specified, the program terminates.	file system is not possible. You should run fsck again to recheck the file system.

To terminate the program, type n.

INCORRECT BLOCK COUNT I=inode-number (number-of-BAD-DUP-or-missing-blocks should be number-of-blocks-in-filesystem) (CORRECT)

Reason Error Occurred................How to Fix the Problem

The block count for inode inode-number is number-of-BAD- To replace the block count of inode inode-number by

DUP-or-missing-blocks, but should be number-of-blocks-in-	number-of-blocks-in-filesystem, type y at the CORRECT
filesystem. When preening, fsck corrects the count.	prompt. To terminate the program, type n.

LINK COUNT TABLE OVERFLOW (CONTINUE)

Reason Error Occurred	How to Fix the Problem
There is no more room in an internal table for fsck	To continue the program, type y at the CONTINUE
containing allocated inodes with a link count of zero. If	prompt. If another allocated inode with a zero-link count
the -o p (preen) option is specified, the program exits	is found, this error condition repeats. When this error
and fsck has to be completed manually.	occurs, a complete check of the file system is not possible. You should run fsck again to recheck the file system. Increase the virtual memory available by killing some processes or increasing swap space, then run fsck again. To terminate the program, type n.
PARTIALLY ALLOCATED INODE I=inode-number (CLEAR)
Reason Error Occurred	How to Solve the Problem
Inode inode-number is neither allocated nor unallocated. If	To deallocate the inode inode-number by zeroing out its

the -o p (preen) option is specified, the inode is cleared. contents, type y. This may generate the UNALLOCATED error condition in phase 2 for each directory entry pointing to this inode.

To ignore the error condition, type n. A no response is appropriate only if you intend to take other measures to fix the problem.

PARTIALLY TRUNCATED INODE I=inode-number (SALVAGE)

Reason Error Occurred	How to Solve the Problem
fsck has found inode inode-number whose size is shorter	To complete the truncation to the size specified in the
than the number of blocks allocated to it. This condition	inode, type y at the SALVAGE prompt.
occurs only if the system crashes while truncating a file.	To ignore this error condition, type n.

When preening the file system, fsck completes the truncation to the specified size.

UNKNOWN FILE TYPE I=inode-number (CLEAR)

Reason Error Occurred	How to Solve the Problem
The mode word of the inode inode-number shows that the	To deallocate the inode inode-number by zeroing its
inode is not a pipe, special character inode, special block	contents, which results in the UNALLOCATED error
inode, regular inode, symbolic link, FIFO file, or	condition in phase 2 for each directory entry pointing to
directory inode. If the -o p option is specified, the inode	this inode, type y at the CLEAR prompt.
is cleared.	To ignore this error condition, type n.

Phase 1B: Rescan for More DUPS Messages

When a duplicate block is found in the file system, this message is displayed:

block-number DUP I=inode-number

Reason Error Occurred	How to Solve the Problem
Inode inode-number contains a block number block-number	When a duplicate block is found, the file system is
that is already claimed by the same or another inode.	rescanned to find the inode that previously claimed that
This error condition generates the BAD/DUP error	block.

message in phase 2. Inodes that have overlapping blocks may be determined by examining this error condition and the DUP error condition in phase 1.

Phase 2: Check Path Names Messages

This phase removes directory entries pointing to bad inodes found in phases 1 and 1B. It reports error conditions resulting from:

• Incorrect root inode mode and status
• Directory inode pointers out of range
• Directory entries pointing to bad inodes
• Directory integrity checks

When the file system is being preened (-o p option), all errors in this phase terminate fsck, except those related to directories not being a multiple of the block size, duplicate and bad blocks, inodes out of range, and extraneous hard links.

Other possible error messages displayed in this phase are referenced below.

• BAD INODE state-number TO DESCEND
• BAD INODE NUMBER FOR '.' I=inode-number OWNER=UID MODE=file-mode SIZE=file-size MTIME=modification-time DIR=filename (FIX)
• BAD INODE NUMBER FOR '..' I=inode-number OWNER=UID MODE=file-mode SIZE=file-size MTIME=modification-time DIR=filename (FIX)
• BAD RETURN STATE state-number FROM DESCEND
• BAD STATE state-number FOR ROOT INODE
• BAD STATE state-number FOR INODE=inode-number

• DIRECTORY TOO SHORT I=inode-number OWNER=UID MODE=file-mode SIZE=file-size MTIME=modification-time DIR=filename (FIX)
• DIRECTORY filename: LENGT file-size NOT MULTIPLE OF block-number (ADJUST)
• DIRECTORY CORRUPTED I=inode-number OWNER=UID MODE=file-mode SIZE=file-size MTIME=modification-time DIR=filename (SALVAGE)
• DUP/BAD I=inode-number OWNER=O MODE=M SIZE=file-size MTIME=modification-time TYPE=filename (REMOVE)
• DUPS/BAD IN ROOT INODE (REALLOCATE)
• EXTRA '.' ENTRY I=inode-number OWNER=UID MODE=file-mode SIZE=file-size MTIME=modification-time DIR=filename (FIX)
• EXTRA '..' ENTRY I=inode-number OWNER=UID MODE=file-mode SIZE=file-size MTIME=modification-time DIR=filename (FIX)
• hard-link-number IS AN EXTRANEOUS HARD LINK TO A DIRECTORY filename (REMOVE)
• inode-number OUT OF RANGE I=inode-number NAME=filename (REMOVE)
• MISSING '.' I=inode-number OWNER=UID MODE=file-mode SIZE=file-size MTIME=modification-time DIR=filename (FIX)
• MISSING '.' I=inode-number OWNER=UID MODE=file-mode SIZE=file-size MTIME=modification-time DIR=filename CANNOT FIX, FIRST ENTRY IN DIRECTORY CONTAINS filename
• MISSING '.' I=inode-number OWNER=UID MODE=file-mode SIZE=file-size MTIME=modification-time DIR=filename CANNOT FIX, INSUFFICIENT SPACE TO ADD '.'
• MISSING '..' I=inode-number OWNER=UID MODE=file-mode SIZE=file-size MTIME=modification-time DIR=filename (FIX)
• MISSING '..' I=inode-number OWNER=UID MODE=file-mode SIZE=file-size MTIME=modification-time DIR=filename CANNOT FIX, SECOND ENTRY IN DIRECTORY CONTAINS filename
• MISSING '..' I=inode-number OWNER=UID MODE=file-mode SIZE=file-size MTIME=modification-time DIR=filename CANNOT FIX, INSUFFICIENT SPACE TO ADD '..'
• NAME TOO LONG filename
• ROOT INODE UNALLOCATED (ALLOCATE)
• ROOT INODE NOT DIRECTORY (REALLOCATE)
• UNALLOCATED I=inode-number OWNER=UID MODE=file-mode SIZE=file-size MTIME=modification-time type=filename (REMOVE)
• ZERO LENGTH DIRECTORY I=inode-number OWNER=UID MODE=file-mode SIZE=file-size MTIME=modification-time DIR=filename (REMOVE)

BAD INODE state-number TO DESCEND

Reason Error Occurred	How to Solve the Problem
An fsck internal error has passed an invalid state state-	If this error message is displayed, contact your local
number to the routine that descends the file system	service provider or another qualified person.

directory structure. fsck exits.

BAD INODE NUMBER FOR '.' I=inode-number OWNER=UID MODE=file-mode SIZE=file-size MTIME=modification-time DIR=filename (FIX)

Reason Error Occurred	How to Solve the Problem
A directory inode-number has been found whose inode	To change the inode number for "." to be equal to inode-
number for "." does not equal inode-number.	number, type y at the FIX prompt. To leave the inode numbers for "." unchanged, type n.
BAD INODE NUMBER FOR '..' I=inode-number OWNER=UID MODE=file-mode SIZE=file-size MTIME=modification-time
Reason Error Occurred	How to Solve the Problem
A directory inode-number has been found whose inode	To change the inode number for ".." to be equal to the
number for ".." does not equal the parent of inode-	parent of inode-number, type y at the FIX prompt. (Note
number.	that "..'' in the root inode points to itself.) To leave the inode number for ".." unchanged, type n.

BAD RETURN STATE state-number FROM DESCEND

Reason Error Occurred	How to Solve the Problem
An fsck internal error has returned an impossible state	If this message is displayed, contact your local service
state-number from the routine that descends the file	provider or another qualified person.

system directory structure. fsck exits.

BAD STATE state-number FOR ROOT INODE

Reason Error Occurred	How to Solve the Problem
An internal error has assigned an impossible state state-	If this error message is displayed, contact your local
number to the root inode. fsck exits.	service provider or another qualified person.
BAD STATE state-number FOR INODE=inode-number
Reason Error Occurred	How to Solve the Problem
An internal error has assigned an impossible state state-	If this error message is displayed, contact your local
number to inode inode-number. fsck exits.	service provider or another qualified person.

DIRECTORY TOO SHORT I=inode-number OWNER=UID MODE=file-mode SIZE=file-size MTIME=modification-time DIR=filename (FIX)

Reason Error Occurred	How to Solve the Problem
A directory filename has been found whose size file-size is	To increase the size of the directory to the minimum
less than the minimum directory size. The owner UID,	directory size, type y at the FIX prompt.
mode file-mode, size file-size, modify time modification-time,	To ignore this directory, type n.

and directory name filename are displayed.

DIRECTORY filename: LENGT file-size NOT MULTIPLE OF block-number (ADJUST)

Reason Error Occurred	How to Solve the Problem
A directory filename has been found with size file-size	To round up the length to the appropriate block size, type
that is not a multiple of the directory block size block-	y. When preening the file system (-o p option), fsck
number.	only displays a warning and adjusts the directory. To ignore this condition, type n.

DIRECTORY CORRUPTED I=inode-number OWNER=UID MODE=file-mode SIZE=file-size MTIME=modification-time DIR=filename (SALVAGE)

Reason Error Occurred	How to Solve the Problem
A directory with an inconsistent internal state has been	To throw away all entries up to the next directory
found.	boundary (usually a 512-byte boundary), type y at the SALVAGE prompt. This drastic action can throw away up to 42 entries. Take this action only after other recovery efforts have failed.

To skip to the next directory boundary and resume reading, but not modify the directory, type n.

DUP/BAD I=inode-number OWNER=O MODE=M SIZE=file-size MTIME=modification-time TYPE=filename (REMOVE)

Reason Error Occurred	How to Solve the Problem
Phase 1 or phase 1B found duplicate blocks or bad blocks	To remove the directory or file entry filename, type y at
associated with directory or file entry filename, inode	the REMOVE prompt.
inode-number. The owner UID, mode file-mode, size file-	To ignore this error condition, type n.

size, modification time modification-time, and directory or file name filename are displayed. If the -p (preen) option is specified, the duplicate/bad blocks are removed.

DUPS/BAD IN ROOT INODE (REALLOCATE)

Reason Error Occurred	How to Solve the Problem
Phase 1 or phase 1B has found duplicate blocks or bad	To clear the existing contents of the root inode and
blocks in the root inode (usually inode number 2) of the	reallocate it, type y at the REALLOCATE prompt. The files
file system.	and directories usually found in the root will be recovered in phase 3 and put into the lost+found directory. If the attempt to allocate the root fails, fsck will exit with: CANNOT ALLOCATE ROOT INODE. To get the CONTINUE prompt, type n. To respond to the CONTINUE prompt, type:

y - To ignore the DUPS/BAD error condition in the root inode and continue running the file system check. If the root inode is not correct, this may generate many other error messages.

n - To terminate the program.

EXTRA '.' ENTRY I=inode-number OWNER=UID MODE=file-mode SIZE=file-size MTIME=modification-time DIR=filename (FIX)

Reason Error Occurred	How to Solve the Problem
A directory inode-number has been found that has more	To remove the extra entry for "." type y at the FIX
than one entry for ".".	prompt. To leave the directory unchanged, type n.

EXTRA '..' ENTRY I=inode-number OWNER=UID MODE=file-mode SIZE=file-size MTIME=modification-time DIR=filename (FIX)

Reason Error Occurred	How to Solve the Problem
A directory inode-number has been found that has more	To remove the extra entry for '..' (the parent directory),
than one entry for ".." (the parent directory).	type y at the FIX prompt. To leave the directory unchanged, type n.
hard-link-number IS AN EXTRANEOUS HARD LINK TO A DIRECTORY filename (REMOVE)
Reason Error Occurred	How to Solve the Problem
fsck has found an extraneous hard link hard-link-number	To delete the extraneous entry hard-link-number type y at
to a directory filename. When preening (-o p option),	the REMOVE prompt. To ignore the error condition, type n.

fsck ignores the extraneous hard links.

inode-number OUT OF RANGE I=inode-number NAME=filename (REMOVE)

Reason Error Occurred	How to Solve the Problem
A directory entry filename has an inode number inode-	To delete the directory entry filename type y at the
number that is greater than the end of the inode list. If the	REMOVE prompt. To ignore the error condition, type n.

-p (preen) option is specified, the inode will be removed automatically.

MISSING '.' I=inode-number OWNER=UID MODE=file-mode SIZE=file-size MTIME=modification-time DIR=filename (FIX)

Reason Error Occurred	How to Solve the Problem
A directory inode-number has been found whose first	To build an entry for "." with inode number equal to
entry (the entry for ".") is unallocated.	inode-number, type y at the FIX prompt. To leave the directory unchanged, type n.
MISSING '.' I=inode-number OWNER=UID MODE=file-mode SIZE=file-size MTIME=modification-time DIR=filename
Reason Error Occurred	How to Solve the Problem
A directory inode-number has been found whose first	Mount the file system and move entry filename elsewhere.
entry is filename. fsck cannot resolve this problem.	Unmount the file system and run fsck again.
MISSING '.' I=inode-number OWNER=UID MODE=file-mode SIZE=file-size MTIME=modification-time DIR=filename
Reason Error Occurred	How to Solve the Problem
A directory inode-number has been found whose first	If this error message is displayed, contact your local
entry is not ".". fsck cannot resolve the problem.	service provider or another qualified person.

MISSING '..' I=inode-number OWNER=UID MODE=file-mode SIZE=file-size MTIME=modification-time DIR=filename (FIX)

Reason Error Occurred	How to Solve the Problem
A directory inode-number has been found whose second	To build an entry for ".." with inode number equal to
entry is unallocated.	the parent of inode-number, type y at the FIX prompt. (Note that "..'' in the root inode points to itself.) To leave the directory unchanged, type n.

MISSING '..' I=inode-number OWNER=UID MODE=file-mode SIZE=file-size MTIME=modification-time DIR=filename CANNOT FIX, SECOND ENTRY IN DIRECTORY CONTAINS filename

Reason Error Occurred................How to Solve the Problem

A directory inode-number has been found whose second	Mount the file system and move entry filename elsewhere.
entry is filename. fsck cannot resolve this problem.	Then unmount the file system and run fsck again.

MISSING '..' I=inode-number OWNER=UID MODE=file-mode SIZE=file-size MTIME=modification-time DIR=filename CANNOT FIX, INSUFFICIENT SPACE TO ADD '..'

Reason Error Occurred................How to Solve the Problem

A directory inode-number has been found whose second	Mount the file system and move the second entry in the
entry is not ".." (the parent directory). fsck cannot	directory elsewhere. Then unmount the file system and
resolve this problem.	run fsck again.

NAME TOO LONG filename

Reason Error Occurred	How to Solve the Problem
An excessively long path name has been found, which	Remove the circular links.

usually indicates loops in the file system name space. This error can occur if a privileged user has made circular links to directories.

ROOT INODE UNALLOCATED (ALLOCATE)

Reason Error Occurred	How to Solve the Problem
The root inode (usually inode number 2) has no allocate-	To allocate inode 2 as the root inode, type y at the
mode bits.	ALLOCATE prompt. The files and directories usually found in the root will be recovered in phase 3 and put into the lost+found directory. If the attempt to allocate the root fails, fsck displays this message and exits: CANNOT ALLOCATE ROOT INODE. To terminate the program, type n.

ROOT INODE NOT DIRECTORY (REALLOCATE)

Reason Error Occurred	How to Solve the Problem
The root inode (usually inode number 2) of the file	To clear the existing contents of the root inode and
system is not a directory inode.	reallocate it, type y at the REALLOCATE prompt. The files and directories usually found in the root will be recovered in phase 3 and put into the lost+found directory. If the attempt to allocate the root fails, fsck displays this message and exits: CANNOT ALLOCATE ROOT INODE

To have fsck prompt with FIX, type n.

UNALLOCATED I=inode-number OWNER=UID MODE=file-mode SIZE=file-size MTIME=modification-time type=filename (REMOVE)

Reason Error Occurred	How to Solve the Problem
A directory or file entry filename points to an unallocated	To delete the directory entry filename, type y at the
inode inode-number. The owner UID, mode file-mode, size	REMOVE prompt. To ignore the error condition, type n.

file-size, modify time modification-time, and file name filename are displayed.

ZERO LENGTH DIRECTORY I=inode-number OWNER=UID MODE=file-mode SIZE=file-size MTIME=modification-time DIR=filename (REMOVE)

Reason Error Occurred	How to Solve the Problem
A directory entry filename has a size file-size that is zero.	To remove the directory entry filename, type y at the
The owner UID, mode file-mode, size file-size, modify time	REMOVE prompt. This results in the BAD/DUP error
modification-time, and directory name filename are	message in phase 4. To ignore the error condition, type n.

displayed.

Phase 3: Check Connectivity Messages

This phase checks the directories examined in phase 2 and reports error conditions resulting from:

• Unreferenced directories
• Missing or full lost+found directories

Other possible error messages displayed in this phase are referenced below.

• BAD INODE state-number TO DESCEND
• DIR I=inode-number1 CONNECTED. PARENT WAS I=inode-number2
• DIRECTORY filename LENGTH file-size NOT MULTIPLE OF block-number (ADJUST)
• lost+found IS NOT A DIRECTORY (REALLOCATE)
• NO lost+found DIRECTORY (CREATE)
• NO SPACE LEFT IN /lost+found (EXPAND)
• UNREF DIR I=inode-number OWNER=UID MODE=file-mode SIZE=file-size MTIME=modification-time (RECONNECT)

BAD INODE state-number TO DESCEND

Reason Error Occurred	How to Solve the Problem
An internal error has caused an impossible state state-	If this occurs, contact your local service provider or
number to be passed to the routine that descends the file	another qualified person.

system directory structure. fsck exits.

DIR I=inode-number1 CONNECTED. PARENT WAS I=inode-number2

Reason Error Occurred	How to Solve the Problem
This is an advisory message indicating a directory inode	N/A

inode-number1 was successfully connected to the lost+found directory. The parent inode inode-number2 of the directory inode inode-number1 is replaced by the inode number of the lost+found directory.

DIRECTORY filename LENGTH file-size NOT MULTIPLE OF block-number (ADJUST)

Reason Error Occurred	How to Solve the Problem
A directory filename has been found with size file-size that	To round up the length to the appropriate block size, type
is not a multiple of the directory block size B. (This	y at the ADJUST prompt. When preening, fsck displays a
condition can recur in phase 3 if it is not adjusted in	warning and adjusts the directory.
phase 2.)	To ignore this error condition, type n.

lost+found IS NOT A DIRECTORY (REALLOCATE)

Reason Error Occurred	How to Solve the Problem
The entry for lost+found is not a directory.	To allocate a directory inode and change the lost+found directory to reference it, type y at the REALLOCATE prompt. The previous inode reference by the lost+found directory is not cleared and it will either be reclaimed as an unreferenced inode or have its link count adjusted later in this phase. Inability to create a lost+found directory displays the message: SORRY. CANNOT CREATE lost+found DIRECTORY and aborts the attempt to link up the lost inode, which generates the UNREF error message in phase 4. To abort the attempt to link up the lost inode, which generates the UNREF error message in phase 4, type n.
NO lost+found DIRECTORY (CREATE)
Reason Error Occurred	How to Solve the Problem
There is no lost+found directory in the root directory	To create a lost+found directory in the root of the file
of the file system. When preening, fsck tries to create a	system, type y at the CREATE prompt. This may lead to
lost+found directory.	the message NO SPACE LEFT IN / (EXPAND). If the lost+found directory cannot be created, fsck displays the message: SORRY. CANNOT CREATE lost+found DIRECTORY and aborts the attempt to link up the lost inode. This in turn generates the UNREF error message later in phase 4. To abort the attempt to link up the lost inode, type n.

NO SPACE LEFT IN /lost+found (EXPAND)

Reason Error Occurred	How to Solve the Problem
Another entry cannot be added to the lost+found	To expand the lost+found directory to make room for
directory in the root directory of the file system because	the new entry, type y at the EXPAND prompt. If the
no space is available. When preening, fsck expands the	attempted expansion fails, fsck displays:
lost+found directory.	SORRY. NO SPACE IN lost+found DIRECTORY and aborts the request to link a file to the lost+found directory. This error generates the UNREF error message later in phase 4. Delete any unnecessary entries in the lost+found directory. This error terminates fsck when preening is in effect.

To abort the attempt to link up the lost inode, type n..

UNREF DIR I=inode-number OWNER=UID MODE=file-mode SIZE=file-size MTIME=modification-time (RECONNECT)

Reason Error Occurred	How to Solve the Problem
The directory inode inode-number was not connected to a	To reconnect the directory inode inode-number into the
directory entry when the file system was traversed. The	lost+found directory, type y at the RECONNECT prompt.
owner UID, mode file-mode, size file-size, and modification	If the directory is successfully reconnected, a CONNECTED
time modification-time of directory inode inode-number are	message is displayed. Otherwise, one of the lost+found
displayed. When preening, fsck reconnects the non-	error messages is displayed.
empty directory inode if the directory size is non-zero.	To ignore this error condition, type n. This error causes
Otherwise, fsck clears the directory inode.	the UNREF error condition in phase 4.

Phase 4: Check Reference Counts Messages

This phase checks the link count information obtained in phases 2 and 3. It reports error conditions resulting from:

• Unreferenced files
• A missing or full lost+found directory

• Incorrect link counts for files, directories, symbolic links, or special files
• Unreferenced files, symbolic links, and directories
• Bad or duplicate blocks in files and directories
• Incorrect total free-inode counts

All errors in this phase (except running out of space in the lost+found directory) are correctable when the file system is being preened.

Other possible error messages displayed in this phase are referenced below.

• BAD/DUP type I=inode-number OWNER=UID MODE=file-mode SIZE=file-size MTIME=modification-time (CLEAR)
• (CLEAR)
• LINK COUNT type I=inode-number OWNER=UID MODE=file-mode SIZE=file-size MTIME=modification-time COUNT link-count SHOULD BE corrected-link-count (ADJUST)
• lost+found IS NOT A DIRECTORY (REALLOCATE)
• NO lost+found DIRECTORY (CREATE)
• NO SPACE LEFT IN /lost+found (EXPAND)
• UNREF FILE I=inode-number OWNER=UID MODE=file-mode SIZE=file-size MTIME=modification-time (RECONNECT)
• UNREF type I=inode-number OWNER=UID MODE=file-mode SIZE=file-size MTIME=modification-time (CLEAR)
• ZERO LENGTH DIRECTORY I=inode-number OWNER=UID MODE=file-mode SIZE=file-size MTIME=modification-time (CLEAR)

BAD/DUP type I=inode-number OWNER=UID MODE=file-mode SIZE=file-size MTIME=modification-time (CLEAR)

Reason Error Occurred	How to Solve the Problem
Phase 1 or phase 1B found duplicate blocks or bad blocks	To deallocate inode inode-number by zeroing its contents,
associated with file or directory inode inode-number. The	type y at the CLEAR prompt.
owner UID, mode file-mode, size file-size, and modification	To ignore this error condition, type n.

time modification-time of inode inode-number are displayed.

(CLEAR)

Reason Error Occurred	How to Solve the Problem
The inode mentioned in the UNREF error message	To deallocate the inode by zeroing out its contents, type y
immediately preceding cannot be reconnected. This	at the CLEAR prompt.
message does not display if the file system is being	To ignore the preceding error condition, type n.

preened because lack of space to reconnect files terminates fsck.

LINK COUNT type I=inode-number OWNER=UID MODE=file-mode SIZE=file-size MTIME=modification-time COUNT link- count SHOULD BE corrected-link-count (ADJUST)

Reason Error Occurred	How to Solve the Problem
The link count for directory or file inode inode-number is	To replace the link count of directory or file inode inode-
link-count but should be corrected-link-count. The owner	number with corrected-link-count, type y at the ADJUST
UID, mode file-mode, size file-size, and modification time	prompt.
modification-time of inode inode-number are displayed. If	To ignore this error condition, type n.

the -o p option is specified, the link count is adjusted unless the number of references is increasing. This condition does not occur unless there is a hardware failure. When the number of references is increasing during preening, fsck displays this message and exits: LINK COUNT INCREASING

lost+found IS NOT A DIRECTORY (REALLOCATE)

Reason Error Occurred	How to Solve the Problem
The entry for lost+found is not a directory.	To allocate a directory inode and change the lost+found directory to reference it, type y at the REALLOCATE prompt. The previous inode reference by the lost+found directory is not cleared. It will either be reclaimed as an unreferenced inode or have its link count adjusted later in this phase. Inability to create a lost+found directory displays this message: SORRY. CANNOT CREATE lost+found DIRECTORY and aborts the attempt to link up the lost inode. This error generates the UNREF error message later in phase 4. To abort the attempt to link up the lost inode, type n.
NO lost+found DIRECTORY (CREATE)
Reason Error Occurred	How to Solve the Problem
There is no lost+found directory in the root directory	To create a lost+found directory in the root of the file
of the file system. When preening, fsck tries to create a	system, type y at the CREATE prompt. If the lost+found
lost+found directory.	directory cannot be created, fsck displays the message: SORRY. CANNOT CREATE lost+found DIRECTORY and aborts the attempt to link up the lost inode. This error in turn generates the UNREF error message later in phase 4.

To abort the attempt to link up the lost inode, type n.

NO SPACE LEFT IN / lost+found (EXPAND)

Reason Error Occurred	How to Solve the Problem
There is no space to add another entry to the	To expand the lost+found directory to make room for
lost+found directory in the root directory of the file	the new entry, type y at the EXPAND prompt. If the
system. When preening, fsck expands the lost+found	attempted expansion fails, fsck displays the message:
directory.	SORRY. NO SPACE IN lost+found DIRECTORY and aborts the request to link a file to the lost+found directory. This error generates the UNREF error message later in phase 4. Delete any unnecessary entries in the lost+found directory. This error terminates fsck when preening (-o p option) is in effect.

To abort the attempt to link up the lost inode, type n.

UNREF FILE I=inode-number OWNER=UID MODE=file-mode SIZE=file-size MTIME=modification-time (RECONNECT)

Reason Error Occurred	How to Solve the Problem
File inode inode-number, was not connected to a directory	To reconnect inode inode-number to the file system in the
entry when the file system was traversed. The owner	lost+found directory, type y. This error may generate
UID, mode file-mode, size file-size, and modification time	the lost+found error message in phase 4 if there are
modification-time of inode inode-number are displayed.	problems connecting inode inode-number to the
When fsck is preening, the file is cleared if either its size	lost+found directory.
or its link count is zero; otherwise, it is reconnected.	To ignore this error condition, type n. This error always invokes the CLEAR error condition in phase 4.

UNREF type I=inode-number OWNER=UID MODE=file-mode SIZE=file-size MTIME=modification-time (CLEAR)

Reason Error Occurred	How to Solve the Problem
Inode inode-number (whose type is directory or file) was	To deallocate inode inode-number by zeroing its contents,
not connected to a directory entry when the file system	type y at the CLEAR prompt.
was traversed. The owner UID, mode file-mode, size file-	To ignore this error condition, type n.

size, and modification time modification-time of inode inode-number are displayed. When fsck is preening, the file is cleared if either its size or its link count is zero; otherwise, it is reconnected.

ZERO LENGTH DIRECTORY I=inode-number OWNER=UID MODE=file-mode SIZE=file-size MTIME=modification-time (CLEAR)

Reason Error Occurred	How to Solve the Problem
A directory entry filename has a size file-size that is zero.	To deallocate the directory inode inode-number by zeroing
The owner UID, mode file-mode, size file-size, modification	out its contents, type y.
time modification-time, and directory name filename are	To ignore the error condition, type n.

displayed.

Phase 5: Check Cylinder Groups Messages

This phase checks the free-block and used-inode maps. It reports error conditions resulting from:

• Allocated inodes missing from used-inode maps
• Free blocks missing from free-block maps
• Free inodes in the used-inode maps
• Incorrect total free-block count
• Incorrect total used inode count

The possible error messages displayed in this phase are referenced below.

• BLK(S) MISSING IN BIT MAPS (SALVAGE)
• CG character-for-command-option: BAD MAGIC NUMBER
• FREE BLK COUNT(S) WRONG IN SUPERBLK (SALVAGE)
• SUMMARY INFORMATION BAD (SALVAGE)
• number-of files, number-of-files used, number-of-files free (number-of frags, number-of blocks, percent fragmentation)
• ***** FILE SYSTEM WAS MODIFIED *****
• filename FILE SYSTEM STATE SET TO OKAY
• filename FILE SYSTEM STATE NOT SET TO OKAY

BLK(S) MISSING IN BIT MAPS (SALVAGE)

Reason Error Occurred	How to Solve the Problem
A cylinder group block map is missing some free blocks.	To reconstruct the free-block map, type y at the SALVAGE
During preening, fsck reconstructs the maps.	prompt. To ignore this error condition, type n.
CG character-for-command-option: BAD MAGIC NUMBER
Reason Error Occurred	How to Solve the Problem
The magic number of cylinder group character-for-	If this occurs, contact your local service provider or
command-option is wrong. This error usually indicates that	another qualified person.

the cylinder group maps have been destroyed. When running interactively, the cylinder group is marked as needing reconstruction. fsck terminates if the file system is being preened.

FREE BLK COUNT(S) WRONG IN SUPERBLK (SALVAGE)

Reason Error Occurred	How to Solve the Problem
The actual count of free blocks does not match the count	To reconstruct the superblock free-block information,
of free blocks in the superblock of the file system. If the	type y at the SALVAGE prompt.
-o p option was specified, the free-block count in the	To ignore this error condition, type n.

superblock is fixed automatically.

SUMMARY INFORMATION BAD (SALVAGE)

Reason Error Occurred	How to Solve the Problem
The summary information is incorrect. When preening,	To reconstruct the summary information, type y at the
fsck recomputes the summary information.	SALVAGE prompt. To ignore this error condition, type n.

Cleanup Phase Messages

Once a file system has been checked, a few cleanup functions are performed. The cleanup phase displays the following status messages.

number-of files, number-of-files used, number-of-files free (number-of frags, number-of blocks, percent fragmentation)

This message indicates that the file system checked contains number-of files using number-of fragment-sized blocks, and that there are number-of fragment-sized blocks free in the file system. The numbers in parentheses break the free count down into number-of free fragments, number-of free full-sized blocks, and the percent fragmentation.

***** FILE SYSTEM WAS MODIFIED *****

This message indicates that the file system was modified by fsck. If this file system is mounted or is the current root (/) file system, reboot. If the file system is mounted, you may need to unmount it and run fsck again; otherwise, the work done by fsck may be undone by the in-core copies of tables.

filename FILE SYSTEM STATE SET TO OKAY

This message indicates that file system filename was marked as stable. fsck with the -m option uses this information to determine that the file system does not need checking.

filename FILE SYSTEM STATE NOT SET TO OKAY

This message indicates that file system filename was not marked as stable. fsck with the -m option uses this information to determine that the file system needs checking.

Modifying Automatic Boot Checking

During boot up, a preliminary check on each file system to be mounted from a hard disk is run using the boot script /sbin/rcS, which checks the root (/) and /usr file systems. The other rc shell scripts then use the fsck command to check each additional file system sequentially. They do not check file systems in parallel. File systems are checked sequentially during booting even if the fsck pass numbers are greater than one.

The /etc/vfstab File

When you run the commands for checking and mounting file systems without specifying a file system directly, the commands step through the file system table (/etc/vfstab) using the information specified in the various fields. The fsck pass field specifies information for file system checking. The mount at boot field specifies information for mounting the file system at boot time.

When you create new file systems, add entries to /etc/vfstab indicating whether they are to be checked and mounted at boot time. See Chapter 34, "Mounting and Unmounting File Systems" for more information about adding entries to the /etc/vfstab file.

Information in the /etc/vfstab file is specific for the slices and file systems for each system. Here is an example of an /etc/vfstab file:

$ more /etc/vfstab #device device mount FS fsck mount mount #to mount to fsck point type pass at boot options# #/dev/dsk/c1d0s2 /dev/rdsk/c1d0s2 /usr ufs 1 yes - /proc - /proc proc - no - fd - /dev/fd fd - no - swap - /tmp tmpfs - yes - /dev/dsk/c0t0d0s0 /dev/rdsk/c0t0d0s0 / ufs 1 no - /dev/dsk/c0t0d0s1 - - swap - no - /dev/dsk/c0t0d0s6 /dev/rdsk/c0t0d0s6 /usr ufs 2 no - /dev/dsk/c0t0d0s7 /dev/rdsk/c0t0d0s7 /opt ufs 3 yes - pluto:/export/svr4/man - /usr/man nfs no yes - $

Table 39-4 describes the function of the fsck pass field.

Table 39-4 fsck pass field

If the fsck pass field is Set To ...	Then ...	Comments
- (hyphen)	The generic fsck command will not check the file system regardless of the state of the file system.	Use a hyphen for read-only file systems, remote file systems, or pseudo file systems, such as /proc, to which checking does not apply.
0 or greater	The file system specific fsck command is called.	When the value is greater for UFS file systems, the file system is not checked.
1 or greater and fsck -o p is used	The file system specific fsck automatically checks UFS file systems in parallel.	The value can be any number greater than 1.

In preen mode, fsck allows only one active file system check per disk, starting a new check only after the previous one is completed. fsck automatically uses the major and minor numbers of the devices on which the file systems reside to determine how to check file systems on different disks at the same time.

When the fsck pass number is 1, file systems are checked sequentially, in the order they appear in the /etc/vfstab file. Usually, the root (/) file system has the fsck pass set to 1.

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Note - fsck does not use the fsck pass number to determine the sequence of file system checking.

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· How to Modify Automatic Checking Done During Booting

1. Become root.

2. Edit /etc/vfstab entries in the fsck pass field, and save the changes. The next time the system is booted, the new values are used.

Interactively Checking and Repairing a UFS File System

You may need to interactively check file systems:

• When they cannot be mounted
• When they develop problems while in use

When an in-use file system develops inconsistencies, error messages may be displayed in the console window or the system may crash.

Before using fsck, you may want to refer to "Syntax and Options for the fsck Command" on page 689 and "Error Messages" on page 643 for more information.

· How to See If a File System Needs Checking

1. Become root.

2. Check the file system.

# fsck -m /dev/rdsk/device-name

In this command, the state flag in the superblock of the file system you specify is checked to see whether the file system is clean or requires checking.

If you omit the device argument, all the UFS file systems listed in /etc/vfstab with a fsck pass value greater than 0 are checked.

Example--Seeing If a File System Needs Checking

In this example, the first file system needs checking; the second file system does not:

# fsck -m /dev/rdsk/c0t0d0s6 ** /dev/rdsk/c0t0d0s6 ufs fsck: sanity check: /dev/rdsk/c0t0d0s6 needs checking # fsck -m /dev/rdsk/c0t0d0s7 ** /dev/rdsk/c0t0d0s7 ufs fsck: sanity check: /dev/rdsk/c0t0d0s7 okay

· How to Check File Systems Interactively

1. Become root.

2. Unmount the local file system except root (/) and /usr.

# umountall -l

3. Check the file system.

# fsck

All file systems in the /etc/vfstab file with entries in the fsck pass field greater than zero are checked. You can also specify the mount point directory or /dev/rdsk/device-name as arguments to fsck. Any inconsistency messages are displayed. See "Error Messages" on page 643 for information about how to respond to the error message prompts to interactively check one or more UFS file systems.

4. If you corrected any errors, type fsck and press Return. fsck may not be able to fix all errors in one execution. If you see the message FILE SYSTEM STATE NOT SET TO OKAY, run the command again. If that does not work, see "How to Fix a UFS File System fsck Cannot Repair" on page 688.

5. Rename and move any files put in the lost+found directory. Individual files put in the lost+found directory by fsck are renamed with their inode numbers. If possible, rename the files and move them where they belong. You may be able to use the grep command to match phrases with individual files and the file command to identify file types. When whole directories are dumped into lost+found, it is easier to figure out where they belong and move them back.

Example--Checking File Systems Interactively

In this example, /dev/rdsk/c0t0d0s6 is checked and the incorrect block count is corrected:

# fsck /dev/rdsk/c0t0d0s6 checkfilesys: /dev/rdsk/c0t0d0s6 ** Phase 1 - Check Block and Sizes INCORRECT BLOCK COUNT I=2529 (6 should be 2) CORRECT? y ** Phase 2 - Check Pathnames ** Phase 3 - Check Connectivity ** Phase 4 - Check Reference Counts ** Phase 5 - Cylinder Groups 929 files, 8928 used, 2851 free (75 frags, 347 blocks, 0.6% fragmentation) /dev/rdsk/c0t0d0s6 FILE SYSTEM STATE SET TO OKAY ***** FILE SYSTEM WAS MODIFIED *****

Preening UFS File Systems

The preen option to fsck (fsck -o p) checks UFS file systems and automatically fixes the simple problems that normally result from an unexpected system halt. It exits immediately if it encounters a problem that requires operator intervention. The preen option also permits parallel checking of file systems.

You can run fsck with the -o p option to preen the file systems after an unclean halt. In this mode, fsck does not look at the clean flag and does a full check. These actions are a subset of the actions that fsck takes when it runs interactively.

· How to Preen a File System

1. Become root.

2. Unmount the file system.

# umount mount-point

3. Check a UFS file system with the preen option.

# fsck -o p /dev/rdsk/device-name

You can preen individual file systems by using mount-point or /dev/rdsk/device-name as arguments to fsck.

Example--Preening a File System

The /usr file system is preened in this example.

# fsck -o p /usr

Restoring a Bad Superblock

When the superblock of a file system becomes damaged, you must restore it. fsck tells you when a superblock is bad. Fortunately, redundant copies of the superblock are stored within a file system. You can use fsck -o b to replace the superblock with one of the copies.

· How to Restore a Bad Superblock

1. Become root.

2. Change to a directory outside the damaged file system.

3. Unmount the file system.

# umount mount-point

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Caution - Be sure to use the -N option with newfs in the next step. If you omit the -N option, you will create a new, empty file system.

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4. Display the superblock values with the newfs -N command.

# newfs -N /dev/rdsk/device-name

The output of this command displays the block numbers that were used for the superblock copies when newfs created the file system.

5. Provide an alternative superblock with the fsck command.

# fsck -F ufs -o b=block-number /dev/rdsk/device-name

fsck uses the alternative superblock you specify to restore the primary superblock. You can always try 32 as an alternative block, or use any of the alternative blocks shown by newfs -N.

Example--Restoring a Bad Superblock

In this example, superblock copy 5264 is restored for the /files7 file system:

# cd / # umount /files7 # newfs -N /dev/rdsk/c0t3d0s7 /dev/rdsk/c0t3d0s7: 163944 sectors in 506 cylinders of 9 tracks, 36 sectors 83.9MB in 32 cyl groups (16 c/g, 2.65MB/g, 1216 i/g) super-block backups (for fsck -b #) at: 32, 5264, 10496, 15728, 20960, 26192, 31424, 36656, 41888, 47120, 52352, 57584, 62816, 68048, 73280, 78512, 82976, 88208, 93440, 98672, 103904, 109136, 114368, 119600, 124832, 130064, 135296, 140528, 145760, 150992, 156224, 161456, # fsck -F ufs -o b=5264 /dev/rdsk/c0t3d0s7 Alternate superblock location: 5264. ** /dev/rdsk/c0t3d0s7 ** Last Mounted on ** Phase 1 - Check Blocks and Sizes ** Phase 2 - Check Pathnames ** Phase 3 - Check Connectivity ** Phase 4 - Check Reference Counts ** Phase 5 - Check Cyl groups 36 files, 867 used, 75712 free (16 frags, 9462 blocks, 0.0% fragmentation) /dev/rdsk/c0t3d0s7 FILE SYSTEM STATE SET TO OKAY ***** FILE SYSTEM WAS MODIFIED ***** #

If the superblock in the root (/) file system becomes damaged and you cannot boot the system, reinstall /kernel/unix and rebuild the root (/) file system with newfs. Because a superblock is created by the newfs command, you do not need to restore it.

How to Fix a UFS File System fsck Cannot Repair

Sometimes you need to run fsck a few times to fix a file system because problems corrected on one pass may uncover other problems not found in earlier passes. fsck does not keep running until it comes up clean, so you must rerun it manually.

Pay attention to the information displayed by fsck. It may help you fix the problem. For example, the messages may point to a bad directory. If you delete the directory, you may find that fsck runs cleanly.

If fsck still cannot repair the file system, you can try to use the fsdb, ff, clri, and ncheck commands to figure out and fix what is wrong. See fsdb(1M), ff(1M), clri(1M), and ncheck(1M) for information about how to use these commands. You may, ultimately, need to re-create the file system and restore its contents from backup media. See Chapter 43, "Restoring Files and File Systems" for information about restoring complete file systems.

If you cannot fully repair a file system but you can mount it read-only, try using cp, tar, or cpio to retrieve all or part of the data from the file system.

If hardware disk errors are causing the problem, you may need to reformat and divide the disk into slices again before re-creating and restoring file systems. Hardware errors usually display the same error again and again across different commands. The format(1M) command tries to work around bad blocks on the disk. If the disk is too severely damaged, however, the problems may persist, even after reformatting. See format(1M) for information about using the format command. See Chapter 29, "SPARC: Adding a Disk" or Chapter 30, "x86: Adding a Disk" for information about installing a new disk.

Syntax and Options for the fsck Command

The fsck command checks and repairs inconsistencies in file systems. It has four options:

• Checks only whether a file system can be mounted (fsck -m)
• Interactively asks for confirmation before making repairs (fsck)
• Assumes yes or no response for all repairs (fsck -y)
• Noninteractively preens the file system, fixing all expected (innocuous) inconsistencies, but exiting when a serious problem is encountered (fsck -o p)

Generic fsck Command Syntax, Options, and Arguments

The fsck command has two components: a generic component and a component specific to each type of file system. The generic commands apply to most types of file systems, while the specific commands apply to only one type of file system. You should always use the generic command, which calls the file system-specific command, as needed.

Usually, you must be superuser to run fsck. You can run the fsck command without being superuser; but to make repairs, you should unmount the file system and you must have read permission for the raw device file for the slice (a potential security hole).

The generic fsck command goes through /etc/vfstab to see what file systems to check. It runs the appropriate file system-specific fsck command on each file system listed, except those excluded by an fsck pass number of - or 0 (UFS only).

The generic fsck command has the following syntax:

/usr/sbin/fsck [-F type] [-V] [-m] [special] /usr/sbin/fsck [-F type] [-V] -[y|Y]|[n|N] [-o specific-options][special]

Table 39-5 describes the options and arguments to the generic fsck command.

Table 39-5 fsck (1 of 3)

Option Type	Option - Generic	Description
Generic	-F	Specifies the file system type (type). If type is not specified on the command line, it is obtained from /etc/vfstab by matching an entry in that file with the special device name specified. If no entry is found, the default local file system type specified in /etc/default/fs is used.
	-V	Echoes the completed command line (verbose). The echoed line includes additional information derived from /etc/vfstab. This option can be used to verify and validate the command line. It does not execute the command.
	-m	Performs a preliminary check only. It returns a code indicating the state of the file system: 0 for "clean" and 32 for "dirty." This option is used by the startup script /etc/bcheckrc to determine whether a file system needs to be checked.
	-y or -Y or -n or -N	Runs the command automatically answering yes or no to all prompts.

Table 39-5 fsck (2 of 3)

Option Type	Option - Generic	Description
	c	Converts an old format file system with statically allocated tables to new format dynamically allocated tables. Static allocation imposes a hard maximum on table size, while dynamic allocation means space for tables can be added as needed after the initial allocation. If the file system is in the new format, convert it to the old format, unless the table allocation exceeds the fixed maximum allowed in the old format. fsck lists the direction of the conversion. In interactive mode, fsck prompts for confirmation before doing the conversion. When you use the -o p option, the conversion is attempted without asking for confirmation. This option is useful when you want to covert a number of file systems at once. You can determine whether a file system is in the old or new format by running the fstyp(1M) command, and looking at the first line displayed.
	w	Checks only file systems that permit write access.
	special	Specifies the mount point or raw device name of one or more file systems. An entry for the mount point must exist in /etc/vfstab. If you omit the special argument, entries in /etc/vfstab with a specified fsck device and a fsck pass number greater than zero are checked. If preening (-o p) is in effect and more than one entry has an fsck pass number greater than 1, file systems on different disks are checked in parallel.

Table 39-5 fsck (3 of 3)

Option Type	Option - Generic	Description
Specific		This is a comma-separated list of options that follow the -o option. Describes the options that are passed to the UFS-specific fsck command for interpretation.
	p	Preens. Runs the command automatically in silent mode, correcting what it can, but exiting when it encounters a problem that requires intervention. This option also enables parallel checking of UFS file systems.
	b=blocknumber	Uses the alternative (redundant) superblock, located at the specified location. This option can be used to repair a bad superblock. You can display a list of alternative superblocks by using the newfs -N command.