Difference between revisions of "Tar"

Latest revision as of 05:29, 20 November 2013

In computing, tar (derived from tape archive) is both a file format (in the form of a type of archive bitstream) and the name of the program used to handle such files.

Example usage

tar pipes

Is far more efficient (and with less problems) to copy files from one location (or machine) to another via tar pipes.

• Copy everything in /foo to the directory /bar preserving permissions and ownership. Do so verbosely and save the stdout to backup.log and stderr to error.log. Finally, background the job in case of terminal timeouts:

% (cd /foo; tar -cf - . ) | (cd /bar; tar --same-owner -xvpf - ) >backup.log 2>error.log &

The exact same idea as above can be done simply with:

% cp -rvp /foo /bar >backup.log 2>error.log &

• You can also use a tar pipe to copy across a network:

% (cd /src; tar -cvf - foo) | (ssh other.machine 'cd /dst; tar -xf -')
#~OR~
tar cf - whatever | ssh remotehost " ( cd /some/path ; tar xf - ) " 
ssh remotehost "( cd /somewhere ; tar cf - something ) " | tar xf -

• Copy everything in /foo to the current directory:

gtar cf - -C /foo . | gtar xvf -

General

• Backup directory /data and /home with tar command (z - compressed; note the /dev/nst0; 'nst0' not 'st0'):

% tar -czf /dev/st0 /data /home
#~OR~
% tar --index-file=foo.log -jcvf /dev/nst0 /data /home
#~OR~
% tar -jcvf /dev/nst0 /data /home 1>stdout 2>stderr  # Using Bash shell
#~OR~
% tar -jcvf /dev/nst0 --label="Backup - `date '+%Y-%m-%d'` - /home" /home 1>stdout 2>stderr

• Display list of files on tape drive:

% tar -tzf /dev/st0
#~OR~
% tar -tvf /dev/st0

• Restore /data directory:

% cd /
% mt -f /dev/st0 rewind
% tar -xzf /dev/st0 data

Backup via ssh

% tar zcvf - /data | ssh root@www.example.com "cat > /backup/data.tar.gz"

• Or, using the dd command:

% tar cvzf - /data | ssh root@www.example.com "dd of=/backup/data.tar.gz"

• Or, backup to a remote tape device:

% tar cvzf - /data | ssh root@www.example.com "cat > /dev/nst0"

• Also, using the mt command to rewind the tape and then dump to it:

% tar cvzf - /data | ssh root@www.example.com $(mt -f /dev/nst0 rewind; cat > /dev/nst0)$

• Finally, restore the data over a ssh session:

% ssh root@www.example.com "cat /backup/data.tar.gz" | tar zxvf -

Miscellaneous commands

• Exclude certain files from a tar archive:

$ tar -zcvf /home/backup.tar.gz --exclude='foo' --exclude='bar' /home/bob
# ~OR~
$ tar -zcv --exclude='foo' --exclude='bar' -f /home/backup.tar.gz /home/bob

• Exclude directories from a tar archive (note: It is usually a good idea to give the absolute path to the directories you wish to exclude):

$ tar -jcvf my_archive.tar.bz2 /dir/to/archive --exclude '/dir/to/exclude1/*' --exclude '/dir/to/exclude2/*'

• Or, list files to exclude in a file (one filename per line):

$ tar -zcvf /home/backup.tar.gz -X exclude.txt /home/bob

• Tar the contents of a directory, but not the directory itself (and exclude specific sub-directories and/or files):

$ cd foo && tar -vcj --exclude='.git' --exclude='.gitignore' -f /home/bob/foo.tar.bz2 . && cd ..
# Then extract to a different directory (and overwrite the contents of the destination directory)
$ tar -jxvf foo.tar.bz2 --overwrite -C /home/bob/bar/

Backup script (example)

Note: Taken from http://wiki.novell.com/index.php/Nbackup

#!/bin/bash
rm /var/log/nightly-backup.*
echo "@Backup Begins ====================" > /var/log/nightly-backup.log
date >> /var/log/nightly-backup.log
date > /var/log/nightly-backup.errors
mt -f /dev/nst0 rewind >> /var/log/nightly-backup.log 2>> /var/log/nightly-backup.errors
echo "-- System backup" >> /var/log/nightly-backup.log
tar cvf /dev/nst0 --label="System Backup - `date '+%d-%B-%Y'`" \
     --totals -X /etc/backup.excludes / \
     >> /var/log/nightly-backup.log 2>> /var/log/nightly-backup.errors
echo "-- NSS Backup" >> /var/log/nightly-backup.log
/opt/novell/sms/bin/nbackup -cvf /dev/nst0 \
     --label="NSS Backup - `date '+%d-%B-%Y'`" \
     -U local-linux-admin-user \
     -P password /media/nss/MOUNTPOINT/ \
     >> /var/log/nightly-backup.log \
     2>> /var/log/nightly-backup.nss
echo "-- Rewinding and Ejecting Tape" >> /var/log/nightly-backup.log
mt -f /dev/nst0 rewoff >> /var/log/nightly-backup.log 2>> /var/log/nightly-backup.errors
date >> /var/log/nightly-backup.log
echo "@Backup Ends ====================" >> /var/log/nightly-backup.log

See also

• mt
• rsync

External links

• tar(1):The GNU version of the tar archiving utility — Linux man page on usr-share-man.org.

Tutorials

• Linux tape backup with mt and tar command - howto
• Howto: Use tar command through network over ssh session
• Howto: Setting up RAID 1 mirroring on a running remote Linux system over ssh connection
• How do I rotate log files?
• Backup shell script to backup selected directories and upload securely (gpg) to FTP server
• Shell script to backup directories & files from your home directory and email them as .tar.gz file
• How do I use cpio command under Linux?
• Automated Backups With rdiff-backup
• Backup / Restore Using NBACKUP and TAR
• How to use TAR
• TAR file format
• How to Write a DAT Tape on Linux
• Using Standard Input and Output