Chapter 22 Backing Up and Restoring File Systems (Overview)
This chapter provides guidelines and planning information
for backing up and restoring file systems by using the ufsdump
and ufsrestore commands.
This is a list of the overview information in this chapter.
Where to Find Backup and Restore Tasks
Definition: Backing Up and Restoring File Systems
Backing up file systems means copying file systems to removable
media, such as tape, to safeguard against loss, damage, or corruption. Restoring file systems means copying reasonably current backup
files from removable media to a working directory.
This
chapter describes the ufsdump and ufsrestore
commands for backing up and restoring UFS file systems. Other commands are
available for copying files and file systems for the purpose of sharing or
transporting files. The following table provides pointers to all commands
that copy individual files and file systems to other media.
Table 22–1 Commands for Backing Up and Restoring Files and File Systems
|
Task
|
Command
|
For More Information
|
|
Back up one or more file systems to a local tape device or a remote
tape device
|
ufsdump
|
Chapter 23, Backing Up Files and File Systems
(Tasks) or Chapter 26, UFS Backup and Restore Commands (Reference)
|
|
Create read-only copies of file systems
|
fssnap
|
Chapter 24, Using UFS Snapshots (Tasks)
|
|
Back up all file systems for systems on a network from a backup server
|
Solstice Backup software
|
Solstice Backup 5.1 Administration Guide
|
|
Back up and restore an NIS+ master server
|
nisbackup and nisrestore
|
System Administration Guide: Naming and Directory Services (FNS and NIS+)
|
|
Copy, list, and retrieve files on tape or diskette
|
tar, cpio, or pax
|
Chapter 27, Copying UFS Files and File Systems (Tasks)
|
|
Copy master disk to a clone disk
|
dd
|
Chapter 27, Copying UFS Files and File Systems (Tasks)
|
|
Restore complete file systems or individual files from removable media
to a working directory
|
ufsrestore
|
Chapter 25, Restoring Files and File Systems (Tasks)
|
Why You Should Back Up File Systems
Backing
up files is one of the most crucial system administration functions. You should
perform regularly scheduled backups to prevent loss of data due to the following
types of problems:
-
System crashes
-
Accidental deletion of files
-
Hardware failures
-
Natural disasters such as fire, hurricanes, or earthquakes
-
Problems when you reinstall or upgrade a system
Planning Which File Systems to Back Up
You
should back up all file systems that are critical to users, including file
systems that change frequently. The following tables provide general guidelines
on the file systems to back up for standalone systems and servers.
Table 22–2 File Systems to Back Up for Standalone Systems
|
File System to Back Up
|
Description
|
Back Up Interval
|
|
root (/) – slice 0
|
This file system contains the kernel and possibly the /var directory. The /var directory might include
frequently modified files such as mail and accounting files.
|
At regular intervals such as weekly or daily
|
|
/usr – slice 6, /opt
|
The installation of new software and new commands typically affects
the /usr and /opt file systems.
The /opt directory is either part of root (/) or is its own file system.
|
Occasionally
|
|
/export/home – slice 7
|
This file system contains the directories and subdirectories of all
users on the standalone system.
|
More often than root (/) or /usr,
perhaps as often as once a day, depending on your site's needs
|
|
/export , /var, or other file
systems
|
During installation of Solaris software, you might have created these
file systems.
|
As your site requires
|
Table 22–3 File Systems to Back Up for Servers
|
File System to Back Up
|
Description
|
Back Up Interval
|
|
root (/) – slice 0
|
This file system contains the kernel and executables.
|
Once a day to once a month depending on your site's needs.
If you frequently add and remove users and systems on the network, you
have to change configuration files in this file system. In this case, you
should do a full backup of the root (/) file system at
intervals between once a week and once a month.
If your site keeps user mail in the /var/mail directory
on a mail server, which client systems then mount, you might want to back
up root (/) daily. Or, backup the /var
directory, if it is a separate file system.
|
|
/export – slice 3
|
This file system can contain the kernel and executables for diskless
clients.
|
Once a day to once a month, depending on your site's needs.
Because the information in this file system is similar to the server's
root directory in slice 0, the file system does not change frequently. You
need to back up this file system only occasionally, unless your site delivers
mail to client systems. Then, you should back up /export
more frequently.
|
|
/usr – slice 6, /opt
|
An optional file system generally used to store non-system software.
|
Once a day to once a month, depending on your site's needs.
These file systems are fairly static and need to be backed up once a
week to once a month.
|
|
/export/home – slice 7
|
This file system contains the home directories of all the users on the
system. The files in this file system are volatile.
|
Once a day to once a week.
|
Choosing the Type of Backup
You
can perform full or incremental backups by using the ufsdump
command. You can create a temporary image of a file system by using the fssnap command. The following table lists the differences between
these types of backup procedures.
Table 22–4 Differences Between Types of Backups
|
Backup Type
|
Result
|
Advantages
|
Disadvantages
|
|
Full
|
Copies a complete file system or directory
|
All data is in one place
|
Requires large numbers of backup tapes that take a long time to write.
Takes longer to retrieve individual files because the drive has to move sequentially
to the point on the tape where the file is located. You might have to search
multiple tapes.
|
|
Snapshot
|
Creates a temporary image of a file system
|
System can be in multiuser mode
|
System performance might degrade while the snapshot is created.
|
|
Incremental
|
Copies only those files in the specified file system that have
changed since a previous backup
|
Easier to retrieve small changes in file systems
|
Finding which incremental tape contains a file can take time. You might
have to go back to the last full backup.
|
Choosing a Tape Device
The following
table shows typical tape devices that are used for storing file systems during
the backup process. The storage capacity depends on the type of drive and
the data being written to the tape. For more information on tape devices,
see Chapter 28, Managing Tape Drives (Tasks).
Table 22–5 Typical Media for Backing Up File Systems
|
Backup Media
|
Storage Capacity
|
|
1/2-inch reel tape
|
140 Mbytes (6250 bpi)
|
|
2.5-Gbyte 1/4–inch cartridge (QIC) tape
|
2.5 Gbytes
|
|
DDS3 4-mm cartridge tape (DAT)
|
12–24 Gbytes
|
|
14-Gbyte 8-mm cartridge tape
|
14 Gbytes
|
|
DLT 7000 1/2-inch cartridge tape
|
35–70 Gbytes
|
High-Level View of Backing Up and Restoring File Systems (Task Map)
Use this task map to identify all the tasks for backing up and restoring
file systems. Each task points to a series of additional tasks, such as determining
the type of backup to perform.
|
Task
|
Description
|
For Instructions
|
|
1. Identify the file systems to back up
|
Identify which file systems need to be backed up on a daily, weekly,
or monthly basis.
|
Planning Which File Systems to Back Up
|
|
2. Determine the type of backup
|
Determine the type of backup you need for the file systems at your site.
|
Choosing the Type of Backup
|
|
3. Create the backup
|
Use one of the following methods:
|
|
|
|
If you want to have full and incremental backups of your file systems,
use the ufsdump command.
|
Chapter 23, Backing Up Files and File Systems
(Tasks)
|
|
|
If you want to create a snapshot of file system while it is active and
mounted, consider using the fssnap command.
|
Chapter 24, Using UFS Snapshots (Tasks)
|
|
|
If you want to create a snapshot of file system while it is active and
mounted, consider using the fssnap command.
|
Chapter 27, Copying UFS Files and File Systems (Tasks)
|
|
4. (Optional) Restore a file system
|
Select the restoration method that is based on the command used to back
up the files or file system:
|
|
|
|
Restore a file system backup that was created with the ufsdump command.
|
Chapter 25, Restoring Files and File Systems (Tasks)
|
|
|
Restore a file system that was created with the tar, cpio, or pax command.
|
Chapter 27, Copying UFS Files and File Systems (Tasks)
|
|
5. (Optional) Restore the root (/) or /usr file system
|
Restoring the root (/) or /usr
file system is more complicated than restoring a non critical file system.
You need to boot from a local CD or from the network while these file systems
are being restored.
|
How to Restore the root (/)
and /usr File Systems
|
Guidelines for Scheduling Backups
A backup
schedule is the schedule that you establish to run the ufsdump command. This section discusses guidelines on the factors
to weigh when you create a backup schedule. This section also includes sample
backup schedules.
The backup schedule that you create depends on the following:
-
Your need to minimize the number of tapes that are used for
backups
-
The time available for doing backups
-
The time available for doing a full restore of a damaged file
system
-
The time available for retrieving individual files that are
accidentally deleted
How Often Should You Do Backups?
If you do not need to minimize time and the number of media that is
used for backups, you can do full backups every day. However, this backup
method is not realistic for most sites, so incremental backups are used most
often. In this case, you should back up your site enough to so that you can
restore files from the last four weeks. This schedule requires at least four
sets of tapes, one set for each week. You would then reuse the tapes each
month. In addition, you should archive the monthly backups for at least a
year. Then, keep yearly backups for a number of years.
Backup Terms and Definitions
The following table describes backup terms and definitions.
|
Term
|
Definition
|
|
Snapshot
|
Creates a temporary image of a file system.
|
|
Full backup
|
Copies a complete file system or directory.
|
|
Incremental backup
|
Copies only those files in the specified file system that have changed
since a previous backup. Incremental backup types include the following:
-
Daily, cumulative – Copies a day's worth of file changes
on Monday. Then, overwrites Monday's backup with file changes from Tuesday,
Wednesday, and so on.
-
Daily, incremental – Copies a day's worth of file changes
so that you have distinct tapes of Monday's changes, Tuesday's changes, and
so on.
-
Weekly cumulative – Copies the files that have changed
during the week and includes the previous week's file changes.
-
Weekly incremental – Copies the files that have changed
during the week since the previous weekly backup.
|
Suggestions for Scheduling Backups
The following table provides
other suggestions for scheduling backups.
Table 22–6 Suggestions for Backup Schedules
|
File Restoration Need
|
Backup Interval
|
Comments
|
|
To restore different versions of files (for example, file systems that
are used for word processing)
|
Do daily incremental backups every working day
Do not reuse the same tape for daily incremental
backups
|
This schedule saves all files modified that day, as well as those files
still on disk that were modified since the last backup of a lower level. However,
with this schedule, you should use a different tape each day because you might
otherwise be unable to restore the needed version of the file.
For example, a file that changed on Tuesday, and again on Thursday,
goes onto Friday's lower-level backup appearing as it did Thursday night,
not Tuesday night. If a user needs the Tuesday version, you cannot restore
it unless you have a Tuesday backup tape (or a Wednesday backup tape). Similarly,
a file that is present on Tuesday and Wednesday, but removed on Thursday,
does not appear on the Friday lower-level backup.
|
|
To quickly restore a complete file system
|
Do lower-level backups more frequently.
|
—
|
|
To back up a number of file systems on the same server
|
Consider staggering the schedule for different file systems.
|
This way you're not doing all level 0 backups on the same day.
|
|
To minimize tapes
|
Increase the level of incremental backups that are done across the week.
|
Only changes from day to day are saved on each daily tape.
|
|
|
Increase the level of backups that are done at the end of the week.
Put each day's and week's incremental backups onto the same tape.
|
Only changes from week to week (rather than the entire month) are saved
on the weekly tapes.
|
|
|
Put each day's and week's incremental backups onto the same tape.
|
To do so, use the no rewind option of the ufsdump
command, such as specifying /dev/rmt/0n.
|
Using Dump Levels to Create Incremental Backups
The
dump level you specify in the ufsdump command (0–9)
determines which files are backed up. Dump level 0 creates a full backup.
Levels 1–9 are used to schedule incremental backups, but have no defined meanings. Levels 1–9 are just a range of numbers
that are used to schedule cumulative or discrete backups. The only meaning
levels 1–9 have is in relationship to each other, as a higher or lower
number. A lower dump number always restarts a full or a cumulative backup.
The following examples show the flexibility of the incremental dump procedure
using levels 1–9.
Example—Dump Levels for Daily, Cumulative Backups
Doing daily, cumulative incremental backups is the most commonly used
backup schedule and is recommended for most situations. The following example
shows a schedule that uses a level 9 dump Monday through Thursday, and a level
5 dump on Friday to restart the process.
Figure 22–1 Incremental Backup: Daily Cumulative
In the preceding example, you could have used other numbers in the 1–9
range to produce the same results. The key is using the same number Monday
through Thursday, with any lower number on Friday. For
example, you could have specified levels 4, 4, 4, 4, 2 or 7, 7, 7, 7, 5.
Example—Dump Levels for Daily, Incremental Backups
The following example
shows a schedule where you capture only a day's work on different tapes. This
type of backup is referred to as a daily, incremental backup. In this case,
sequential dump level numbers are used during the week (3, 4, 5, 6) with a
lower number (2) on Friday. The lower number on Friday restarts the processing.
Figure 22–2 Incremental Backup: Daily Incremental
In the preceding example, you could have used the sequence 6, 7, 8,
9 followed by 2, or 5, 6, 7, 8 followed by 3. Remember, the numbers themselves
have no defined meaning. You attribute meaning by ordering them in a specified
sequence, as described in the examples.
Sample Backup Schedules
This section provides sample backup
schedules. All schedules assume that you begin with a full backup (dump level
0), and that you use the -u option to record each backup in
the /etc/dumpdates file.
Example—Daily Cumulative, Weekly Cumulative Backups
Table 22–7 shows the most commonly used incremental
backup schedule. This schedule is recommended for most situations. With this
schedule, the following occurs:
-
All files that have changed since the lower-level backup at
the end of the previous week are saved each day.
-
For each weekday level 9 backup, the previous level 0 or level
5 backup is the closest backup at a lower level. Therefore, each weekday tape
contains all the files that changed since the end of the previous week or
the initial level 0 backup for the first week.
-
For each Friday level 5 backup, the closest lower-level backup
is the level 0 backup done at the beginning of the month. Therefore, each
Friday's tape contains all the files changed during the month up to that point.
Table 22–7 Daily Cumulative or Weekly Cumulative Backup Schedule
|
|
Floating
|
Mon
|
Tues
|
Wed
|
Thurs
|
Fri
|
|
1st of Month
|
0
|
|
|
|
|
|
|
Week 1
|
|
9
|
9
|
9
|
9
|
5
|
|
Week 2
|
|
9
|
9
|
9
|
9
|
5
|
|
Week 3
|
|
9
|
9
|
9
|
9
|
5
|
|
Week 4
|
|
9
|
9
|
9
|
9
|
5
|
The following table shows how the contents of the tapes can change across
two weeks with the daily cumulative, weekly cumulative schedule. Each letter
represents a different file.
Table 22–8 Contents of Tapes for Daily Cumulative/Weekly Cumulative Backup Schedule
|
|
Mon
|
Tues
|
Wed
|
Thurs
|
Fri
|
|
Week 1
|
a b
|
a b c
|
a b c d
|
a b c d e
|
a b c d e f
|
|
Week 2
|
g
|
g h
|
g h i
|
g h i j
|
a b c d e f g h i j k
|
Tape Requirements for the Daily Cumulative, Weekly Cumulative Schedule
With this schedule, you need six tapes if you want to reuse daily tapes.
However, you need nine tapes if you want to use four different daily tapes:
If you need to restore a complete file system, you need the following
tapes:
Example—Daily Cumulative, Weekly Incremental Backups
The
following table shows a schedule where each weekday tape accumulates all files
that changed since the beginning of the week, or the initial level 0 backup
for the first week. In addition, each Friday's tape contains all the files
that changed that week.
Table 22–9 Daily Cumulative, Weekly Incremental Backup Schedule
|
|
Floating
|
Mon
|
Tues
|
Wed
|
Thurs
|
Fri
|
|
1st of Month
|
0
|
|
|
|
|
|
|
Week 1
|
|
9
|
9
|
9
|
9
|
3
|
|
Week 2
|
|
9
|
9
|
9
|
9
|
4
|
|
Week 3
|
|
9
|
9
|
9
|
9
|
5
|
|
Week 4
|
|
9
|
9
|
9
|
9
|
6
|
The following table shows how the contents of the tapes can change across
two weeks with the daily cumulative, weekly incremental backup schedule. Each
letter represents a different file.
Table 22–10 Contents of Tapes for Daily Cumulative, Weekly Incremental Backup Schedule
|
|
Mon
|
Tues
|
Wed
|
Thurs
|
Fri
|
|
Week 1
|
a b
|
a b c
|
a b c d
|
a b c d e
|
a b c d e f
|
|
Week 2
|
g
|
g h
|
g h i
|
g h i j
|
g h i j k
|
Tape Requirements for the Daily Cumulative, Weekly Incremental Backup
Schedule
With this schedule, you need six tapes if you want to reuse daily tapes.
However, you need nine tapes if you want to use four different daily tapes:
If you need to restore a complete file system, you need the following
tapes:
Example—Daily Incremental, Weekly Cumulative Backups
The following table shows a schedule where each weekday tape contains only
the files that changed since the previous day. In addition, each Friday's
tape contains all files changed since the initial level 0 backup at the beginning
of the month.
Table 22–11 Daily Incremental, Weekly Cumulative Backup Schedule
|
|
Floating
|
Mon
|
Tues
|
Wed
|
Thurs
|
Fri
|
|
1st of Month
|
0
|
|
|
|
|
|
|
Week 1
|
|
3
|
4
|
5
|
6
|
2
|
|
Week 2
|
|
3
|
4
|
5
|
6
|
2
|
|
Week 3
|
|
3
|
4
|
5
|
6
|
2
|
|
Week 4
|
|
3
|
4
|
5
|
6
|
2
|
The following table shows how the contents of the tapes can change across
two weeks with the daily incremental, weekly cumulative schedule. Each letter
represents a different file.
Table 22–12 Contents of Tapes for Daily Incremental, Weekly Cumulative Backup Schedule
|
|
Mon
|
Tues
|
Wed
|
Thurs
|
Fri
|
|
Week 1
|
a b
|
c d
|
e f g
|
hi
|
a b c d e f g h i
|
|
Week 2
|
j k l
|
m
|
n o
|
p q
|
a b c d e f g h i j k l m n o p q r s
|
Tape Requirements for Daily Incremental, Weekly Cumulative Schedule
With this schedule, you need at least 9 tapes if you want to reuse daily
tapes, which is not recommended. Preferably, you need 21 tapes if you save
weekly tapes for a month: one tape for the level 0, four tapes for the Fridays,
and four or 16 daily tapes.
If you need to restore the complete file system, you need the following
tapes:
Example—Monthly Backup Schedule for a Server
The following table shows an example
backup strategy for a heavily used file server on a small network where users
are doing file-intensive work, such as program development or document production.
This example assumes that the backup period begins on a Sunday and consists
of four seven-day weeks.
Table 22–13 Example of Monthly Backup Schedule for a Server
|
Directory
|
Date
|
Dump Level
|
Tape Name
|
|
root (/)
|
1st Sunday
|
0
|
n tapes
|
|
/usr
|
1st Sunday
|
0
|
n tapes
|
|
/export
|
1st Sunday
|
0
|
n tapes
|
|
/export/home
|
1st Sunday
|
0
|
n tapes
|
|
|
1st Monday
|
9
|
A
|
|
|
1st Tuesday
|
9
|
B
|
|
|
1st Wednesday
|
5
|
C
|
|
|
1st Thursday
|
9
|
D
|
|
|
1st Friday
|
9
|
E
|
|
|
1st Saturday
|
5
|
F
|
|
root (/)
|
2nd Sunday
|
0
|
n tapes
|
|
/usr
|
2nd Sunday
|
0
|
n tapes
|
|
/export
|
2nd Sunday
|
0
|
n tapes
|
|
/export/home
|
2nd Sunday
|
0
|
n tapes
|
|
|
2nd Monday
|
9
|
G
|
|
|
2nd Tuesday
|
9
|
H
|
|
|
2nd Wednesday
|
5
|
I
|
|
|
2nd Thursday
|
9
|
J
|
|
|
2nd Friday
|
9
|
K
|
|
|
2nd Saturday
|
5
|
L
|
|
root (/)
|
3rd Sunday
|
0
|
n tapes
|
|
/usr
|
3rd Sunday
|
0
|
n tapes
|
|
/export
|
3rd Sunday
|
0
|
n tapes
|
|
/export/home
|
3rd Sunday
|
0
|
n tapes
|
|
|
3rd Monday
|
9
|
M
|
|
|
3rd Tuesday
|
9
|
N
|
|
|
3rd Wednesday
|
5
|
O
|
|
|
3rd Thursday
|
9
|
P
|
|
|
3rd Friday
|
9
|
Q
|
|
|
3rd Saturday
|
5
|
R
|
|
root (/)
|
4th Sunday
|
0
|
n tapes
|
|
/usr
|
4th Sunday
|
0
|
n tapes
|
|
/export
|
4th Sunday
|
0
|
n tapes
|
|
/export/home
|
4th Sunday
|
0
|
n tapes
|
|
|
4th Monday
|
9
|
S
|
|
|
4th Tuesday
|
9
|
T
|
|
|
4th Wednesday
|
5
|
U
|
|
|
4th Thursday
|
9
|
V
|
|
|
4th Friday
|
9
|
W
|
|
|
4th Saturday
|
5
|
X
|
With this schedule, you use 4n tapes, the
number of tapes needed for 4 full backups of the root (/), /usr, /export, and /export/home file systems. Also, you need 24 additional tapes for the incremental
backups of the /export/home file systems. This schedule
assumes that each incremental backup uses one tape and that you save the tapes
for a month.
Here's how this schedule works:
-
On each Sunday, do a full backup (level 0) of the root (/), /usr, /export, and /export/home file systems. Save the level 0 tapes for at least
three months.
-
On the first Monday of the month, use tape A to do a level
9 backup of the /export/home file system. The ufsdump command copies all files changed since the previous lower-level
backup. In this case, the previous lower-level backup is the level 0 backup
that you did on Sunday.
-
On the first Tuesday of the month, use tape B to do a level
9 backup of the /export/home file system. Again, the ufsdump command copies all files changed since the last lower-level
backup, which is Sunday's level 0 backup.
-
On the first Wednesday of the month, use tape C to do a level
5 backup of the /export/home file system. The ufsdump command copies all files that changed since Sunday.
-
Do the Thursday and Friday level 9 backups of the /export/home file system on tapes D and E. The ufsdump command copies all files that changed since the last lower-level
backup, which is Wednesday's level 5 backup.
-
On the first Saturday of the month, use tape F to do a level
5 backup of /export/home. The ufsdump
command copies all files changed since the previous lower-level backup (in
this case, the level 0 backup you did on Sunday). Store tapes A-F until the
first Monday of the next four-week period, when you use them again.
-
Repeat steps 1–6 for the next three weeks, using tapes
G–L and 4n tapes for the level 0 backup on
Sunday, and so on.
-
For each four-week period, repeat steps 1–7, using a
new set of tapes for the level 0 backups and reusing tapes A–X for the
incremental backups. The level 0 tapes could be reused after three months.
This schedule lets you save files
in their various states for a month. This plan requires many tapes, but ensures
that you have a library of tapes to draw upon. To reduce the number of tapes,
you could reuse Tapes A–F each week.
Ladda ner denna bok i PDF (1889 KB)