Tar

In computing, tar (derived from tape archive) is both 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

• Copy everything in /foo, to the directory /bar preserving permissions, you can use:

% (cd /foo; tar -cf - . ) | (cd /bar; tar -xpf - )

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

% (cd /src; tar -cvf - foo) | (ssh other.machine 'cd /dst; tar -xf -')

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

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

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