Difference between revisions of "Mt"

Revision as of 01:24, 2 February 2007

The correct title of this article is mt. The initial letter is capitalized due to technical restrictions.

mt is a command used to control and backup data onto magnetic tapes.

Consult the man pages for mt and st for extended information. Also, make sure the modules for st have been loaded with lsmod.

Example usage

Note: The default device name should be /dev/st0 (i.e. first SCSI tape device).

• Rewind tape drive:

% mt -f /dev/st0 rewind

• 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

• Return ("tell") current block:

% mt -f /dev/st0 tell

• 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

• Unload (i.e. enable eject) the tape:

% mt -f /dev/st0 offline

• Display status information about the tape unit:

% mt -f /dev/st0 status

• Erase the tape:

% mt -f /dev/st0 erase

• Go to end of data:

% mt -f /dev/nst0 eod

• Goto previous record:

% mt -f /dev/nst0 bsfm 1

• Forward record:

% mt -f /dev/nst0 fsf 1

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

• Eject the tape (or CDROM, DVD, etc):

% eject /media/cdrom

• Close the tray:

% eject -t /media/cdrom

• 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

Linux tape drives naming conventions

SCSI tape device names

The st driver provides the interface to a variety of SCSI tape devices under Linux.

• First (auto rewind) SCSI tape device name: /dev/st0
• Second (auto rewind) SCSI tape device name: /dev/st1
• First the non-rewind SCSI tape devices: /dev/nst0
• Second the non-rewind SCSI tape devices: /dev/nst1

IDE tape device names

The ht driver provides the interface to a variety of IDE tape devices under Linux.

• First (auto rewind) IDE tape device name: /dev/ht0
• Second (auto rewind) IDE tape device name: /dev/ht1
• First the non-rewind IDE tape devices: /dev/nht0
• Second the non-rewind IDE tape devices: /dev/nht1

Main tape types

• Digital Data Storage (DDS);
• Digital Audio Tape (DAT); and
• Digital Linear Tape (DLT)

See also

• tar
• rsync

External links

• Linux tape backup with mt and tar command - howto
• Howto: Use tar command through network over ssh session
• Tape drives naming convention under Linux
• 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