PAGEFLOP
FORWARD
SELECTOR
SELAGAIN
WRONGSEL
YOUR SELECTION IS NOT IN THE 0 - #SELIMIT RANGE Please try again
GO
Copyright CourseWare Technologies Inc., 1985-88
Lesson - 7
BACKUP AND RESTORE PROCEDURES
MENU
Backups-Restores|Topics to Learn|7-0|12,44
# Topic
--- -------
1 - Purpose of Backups
2 - Backup Types
3 - Selecting A Backup Strategy
4 - Backing Up with the tar Command
5 - Backing Up with the cpio Command
6 - Backing Up with the backup/dump Command
7 - Restoring Files and Directories
8 - Other Backup Utilities
9 - Lesson Review
8 - Lesson Review
0 - Return to the Main Menu
P1
Backups-Restores|Purpose of Backups|7-1.1|4,55
Backing up is the process of saving the data from
your computer's hard disk(s) onto a 9-track tape,
data cartridge, diskettes, or other form of removable
storage media.
P2
Backups-Restores|Purpose of Backups|7-1.2|10,53
Data loss occurs due to equipment failure and
human error.
Backups are done to enable the recovery of
lost data/files.
The procedure of recovering or copying the data
from the backup media back to the hard disk is called
restoring.
P3
Backups-Restores|Backup Types|7-2.1|7,50
There are two types of backups:
1. Full or epoch backups save all of the
data on the entire computer system.
2. Incremental backups save only the data
that was modified since the last full backup.
P4
Backups-Restores|Backup Types|7-2.2|12,58
Incremental backups can be set up to save all of
the data since:
* The last full backup
* The last incremental backup
* an incremental backup of a specified number of
days ago.
One must keep in mind that the most complete backup
permits the fastest complete restore; however, it requires
the maximum media and maximum backup time.
P5
Backups-Restores|Selecting A Backup Strategy|7-3.1|9,52
Since you do not want to lose the information on
your system disk due to mechanical failure or human
error, it is important that you do frequent backups of
your files.
One should select the backup strategy that will
optimize data security, backup-restore time, and
media requirements.
P6
Backups-Restores|Selecting A Backup Strategy|7-3.2|10,58
It is suggested that whenever a significant amount
of new data is being added or changed, a backup of at
least the new information should be done on a daily
basis!
A full dump every week is recommended. You should
perform an incremental backup daily. Furthermore a
strategy has to be devised so there is an overlap of
backed up data in case a volume is lost.
P7
Backups-Restores|Selecting A Backup Strategy|7-3.3|7,60
We shall discuss the following backup and recovery tools:
* tar (for tape archiver),
* cpio (for copy archives in and out),
* volcopy,
* dump/backup, and
* restore.
P8
Backups-Restores|Selecting A Backup Strategy|7-3.4|13,54
First, we'll compare the various commands, then we'll
describe each one in detail.
The tar command:
* won't automatically locate modified files,
* is very reliable and portable, and
* works recursively, i.e., maintains the tree
hierarchy.
The dump or backup command is:
* faster than tar or cpio,
* more efficient than tar or cpio, and
* leaves a time stamp.
P9
Backups-Restores|Selecting A Backup Strategy|7-3.5|14,54
The cpio command:
* is more space efficient than tar,
* has an archive containing pathname and status
information,
* has a format portable across all UNIX-like
systems, BUT
* is more difficult to use, and
* does not handle directory hierarchies.
The volcopy command:
* is just for System V,
* does label checking, and
* creates new volumes that do not have files scattered
all over the disks.
P10
Backups-Restores|Selecting A Backup Strategy|7-3.6|10,50
The tar and cpio commands permit the system
manager and ordinary users to make copies of the
desired directories and files. However, these commands
do not automatically locate modified files.
You have to use the find command to build the
list of modified files and use this list as an
argument to tar and cpio commands.
P11
Backups-Restores|Backups Using tar|7-4.1|5,53
The tar command is one of the most reliable
commands for data storage, portability and recovery.
It was originally designed to operate on magnetic
tapes; however it also permits one to copy files to
or from other magnetic disks.
P12
Backups-Restores|Backups Using tar|7-4.2|11,55
The format of the tar command for archiving is:
tar cvf specialfile files
where f expects specialfile to be the name of the file
corresponding to a disk drive, c creates a new archive,
and v is for verbose.
Unless otherwise indicated, the default device
for tar is the magnetic tape drive.
P13
Backups-Restores|Backups Using tar|7-4.3|5,54
If a file system is mounted on the directory a1,
to back up that file system onto the device rfd0, the
command would be:
tar cf /dev/rfd0 /a1
P14
Backups-Restores|Backups Using tar|7-4.4|11,51
The tar command works recursively when copying
a file system. It assumes that the second argument
is a directory; therefore it looks for files in that
directory. If it finds another directory, it tries
to copy the files from that directory until there are
no directories on the lower levels.
If the argument is an ordinary file then obviously
there are no files below it, and tar copies only
that file in the hierarchy.
P15
Backups-Restores|Backups Using tar|7-4.5|14,57
The command to copy all of the files on the system
to tape drive 5, is:
tar c5 /
Note: Make sure that your archiving medium is large
enough for storing all the files that you plan to back up!
To archive the entire current directory into the
file admin.tar, you would use the following command:
tar cf admin.tar *
P16
Backups-Restores|Backups Using tar|7-4.6|10,46
To check the contents of the new archive
called admin.tar, the command would be:
tar tf admin.tar
To copy the entire tree-structure of the
current directory to a directory called
/a/bin/distribute, use:
tar cf - . | (cd /a/bin/distribute; tar xf -)
P17
Backups-Restores|Backups Using cpio|7-5.1|8,52
The cpio command (copy archives in and out)
is similar to tar. It copies files into and out
of an archive. The archive contains pathname and
status information. However, rather than reading
the pathnames, cpio reads the standard input to
obtain a list of pathnames and copies those files
onto the standard output together with the pathname
and status information.
P18
Backups-Restores|Backups Using cpio|7-5.2|12,60
The format of the cpio archiving command is:
ls pathname(s) -print | cpio -ocBv > specialfile
pathname is the pathname of every file to be
archived;
specialfile is the name of the file corresponding to
a disk drive;
B means to Block 5120 bytes per record;
c means to create ASCII header information;
v indicates to verbosely list the filenames.
P19
Backups-Restores|Backups Using cpio|7-5.3|12,54
To archive all files and subdirectories in the
/usr/CTI directory and put them on the storage
find /usr/CTI -print | cpio -ocBv > /dev/rst
find /usr/CTI -print | cpio -ocBv > /dev/fd0
find /usr/CTI -print | cpio -ocBv > /dev/rmt0
The command to produce a cpio archive of all
of the files ending in .c and put them on the device
/dev/rfd148ds9 would be:
ls *.c | cpio -oBv > /dev/rfd148ds9
P20
Backups-Restores|Backups Using backup/dump|7-6.1|10,55
When the number of users on the system grows, a
special-purpose backup utility like backup or dump
should be used because:
* It is faster than tar or cpio.
* It is more efficient than tar or cpio.
* It leaves a time stamp in a special file of the
backup level.
P21
Backups-Restores|Backups Using backup/dump|7-6.2|13,54
The actual command that performs backup is backup
under UNIX. Under 4.3 BSD systems the utility that
performs an identical function is dump.
The syntax for the backup and dump commands is:
backup [options [device name] file system]
dump [options [device name] file system]
where the device name is the name of the tape device and
file system is the name of the file system to be dumped.
P22
Backups-Restores|Backups Using backup/dump|7-6.3|5,54
Depending on the options and arguments chosen, the
backup utility can save from single files to entire
file systems. Furthermore, it allows you to select
data to backup based on a specified time of last
modification.
P23
Backups-Restores|Backups Using backup/dump|7-6.4|9,52
The backup level (0-9) permits one to specify
which files to backup for the same file system from
the last date stored in the /etc/ddate (or
/etc/dumpdates for BSD systems) for the same file
system.
Level 0 causes the entire file system to be
backed up.
P24
Backups-Restores|Backups Using backup/dump|7-6.5|10,56
Similarly, backup/dump permits one to perform
incremental backups of various levels.
Note how the command interprets the backup dates:
* Level 9 causes the files modified since last
full backup to be backed up.
* Level 5 causes the files modified since the
last level 5 or higher backup to be backed up.
P25
Backups-Restores|Restoring Files and Directories|7-7.1|14,54
Restoring files from archives is the opposite of
the backup procedure. You may restore single files as
well as entire file systems.
The program to use for restoring files depends upon
which program was used for the archive:
program used to make archive program used to restore
---------------------------- -----------------------
tar tar
cpio cpio
dump restore
backup restore
P26
Backups-Restores|Restoring Files and Directories|7-7.2|15,55
Some general points about restoring files:
Never restore a file to it's original directory.
(You could overwrite a better version.) You must make
a new directory (and make sure the user owns it) or
restore files to /usr/tmp.
When restoring files, you must know whether
your system restores the files by names or inode
numbers.
Often you must specify the complete pathname of
the desired file.
P27
Backups-Restores|Restoring Files and Directories|7-7.3|12,55
Some more general points about restoring files:
If the system restores the files by their inode
numbers, you will have to move the file to the desired
name, e.g.:
mv 337 /usr/CTI/admin/7sa
After restoring files, check the ownership and
permissions and send a message to the user telling him
or her where the files are.
P28
Backups-Restores|Restoring Files and Directories|7-7.4|15,55
Prior to restoring files or file systems, it
is a good idea to check the table of contents of the
volume from which you plan to restore these files.
As you saw earlier, the tar command that allows one
to check the contents of an archive is:
tar tvf archive name
The restore command which allows you to check
the contents of an archive that was made using dump is:
restore t
P29
Backups-Restores|Restoring Files and Directories|7-7.5|10,51
The command that allows you to check the
table of contents on an archive made with cpio is:
cpio -t
The command that allows one to check the table
of contents on an archive made with backup is:
dumpdir
P30
Backups-Restores|Restoring with tar|7-7.6|14,45
With the tar program, you may restore an
entire archive, a directory, or a single file.
The syntax for using the tar command to
restore all files from the disk is:
tar xvf specialfile
For example, the command to restore
tar xvf /dev/fd1
tar xvf /dev/rst
tar xvf /dev/rmt0
P31
Backups-Restores|Restoring with tar|7-7.7|12,54
To restore a single file or directory you need
to list the contents of the directory. For example,
to get a verbose listing of the archive /dev/rfd0
with a blocking factor of 20 you would type:
tar tvbf 20 /dev/rfd0
To restore all files starting with the directory
name cti from the archive /dev/rfd0, you would use
the command:
tar xf /dev/rfd0 cti/*
P32
Backups-Restores|Restoring with cpio|7-7.8|13,55
The command to extract all the files that are archived
in cpio format is:
cpio -i [Bcdmrtuv] [patterns]
where patterns can be any of the name-generating notations
of sh or csh.
For example, to restore all of the files whose names end in
*.summary from the device /dev/fd1
the command would be:
cpio -idv *.summary < /dev/fd1
P33
Backups-Restores|Restoring with restore|7-7.9|9,46
For files archived with backup or dump the
restore function is performed with the restore
command.
It is possible to restore:
* 1 or more particular files or
* an entire file system.
Backups-Restores|Restoring with restore|7-7.9|13,46
For files archived with backup or dump the
restore function is performed with the restore
command.
It is possible to restore:
* 1 or more particular files or
* an entire file system.
The restore function is also available
through the sysadmin menu.
Backups-Restores|Restoring with restore|7-7.9|16,50
For files archived with backup or dump the
restore function is performed with the restore
command.
It is possible to restore:
* 1 or more particular files or
* an entire file system.
The restore function may also be available
through the admin menu.
Note that the utility volcopy may be used
to perform full restores as well.
P34
Backups-Restores|Restoring Files with restore|7-7.10|12,55
The general steps for restoring files are:
1. locate the appropriate tape(s),
2. mount the tape,
3. determine the name of the device it's mounted on,
4. cd /usr/tmp to avoid overwriting files with the same name,
5. type restore t to read the table of contents,
6. identify the files to be restored,
7. restore the files with restore,
8. check ownership and permissions, and
9. notify the owner about the location of the restored
files.
P35
Backups-Restores|Restoring Files with restore|7-7.11|12,55
You can also use the restore command interactively
by typing restore -i When you do so, you can browse
through directories to create a list of files to be
restored using interactive commands like:
help - display a summary of available commands
cd dir - change to the named directory
ls [dir] - list the files in dir
add file - add the named file to the list of
files to extract
delete file - delete the named file from the list
extract - extract all files on the list
P36
Backups-Restores|Restoring Files with restore|7-7.12|12,55
The command to rewind a reel of 1/2 inch tape and
take it off-line is:
mt offline
For 1/4 inch tapes (on data cartridges) you must
add a option to indicate which device. The command to
do this is
mt -f /dev/devicename offline
P37
Backups-Restores|Restoring Files and Directories|7-7.13|7,52
Backups-Restores|Restoring Files and Directories|7-7.11|7,52
Backup and restore procedures may not be the
most interesting tasks; however, they are some of
the most important system maintenance tasks.
As a system administrator, you should
understand these clearly prior to storing important
files on your system.
P38
Backups-Restores|Other Backup Utilities|7-8.1|11,56
The command volcopy can be used to backup or copy
entire file systems (with label checking) to mounted
volumes. This utility is similar to the DOS copy
utility. To copy volume 2 of the file system is mounted
on device /dev/rfd0 onto volume 1 of /dev/rfud1 use:
volcopy is /dev/rfd0 2 /dev/rfud1 1
Many UNIX systems offer a menu-level interface
for performing backups.
Backups-Restores|Other Backup Utilities|7-8.1|6,54
Many UNIX systems offer a menu-level interface
for performing backups.
Under Xenix this utility is called sysadmin
which uses the backup command.
P39
Backups-Restores|Other Backup Utilities|7-8.2|14,60
To use the system backup utility sysadmin
1. Login as root.
2. Type at the prompt: sysadmin. The program
will display the file system maintenance menu, e.g.:
File System Maintenance
-----------------------
1 to do daily backup
2 to do a periodic backup
3 to get a backup listing
4 to restore a file
5 to quit
3. Select the desired choice and follow the interactive
procedure.
Backups-Restores|Other Backup Utilities|7-8.2|14,60
The command for specifying initial labels for
unmounted disks and file systems is /etc/labelit. The
labels produced by labelit are used by volcopy when
copying files onto these mounted file systems.
When used with no arguments, labelit prints
the label information on the file system.
The command to specify label mt of version mt.3
for a new magnetic tape on device /dev/rmt3 is:
labelit /dev/rmt3 mt mt.3 -n