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Chapter 17. Managing tape devices
A tape device is a magnetic tape where data is stored and accessed sequentially. Data is written to this tape device with the help of a tape drive. There is no need to create a file system in order to store data on a tape device. Tape drives can be connected to a host computer with various interfaces like, SCSI, FC, USB, SATA, and other interfaces.
17.1. Types of tape devices
The following is a list of the different types of tape devices:
-
/dev/st0
is a rewinding tape device. -
/dev/nst0
is a non-rewinding tape device. Use non-rewinding devices for daily backups.
There are several advantages to using tape devices. They are cost efficient and stable. Tape devices are also resilient against data corruption and are suitable for data retention.
17.2. Installing tape drive management tool
Install the mt-st
package for tape drive operations. Use the mt
utility to control magnetic tape drive operations, and the st
utility for SCSI tape driver.
Procedure
Install the
mt-st
package:# dnf install mt-st
Additional resources
-
mt(1)
andst(4)
man pages on your system
17.3. Tape commands
The following are the common mt
commands:
Command | Description |
---|---|
| Displays the status of the tape device. |
| Erases the entire tape. |
| Rewinds the tape device. |
| Switches the tape head to the forward record. Here, n is an optional file count. If a file count is specified, tape head skips n records. |
| Switches the tape head to the previous record. |
| Switches the tape head to the end of the data. |
17.4. Writing to rewinding tape devices
A rewind tape device rewinds the tape after every operation. To back up data, you can use the tar
command. By default, in tape devices the block size
is 10KB (bs=10k
). You can set the TAPE
environment variable using the export TAPE=/dev/st0
attribute. Use the -f
device option instead, to specify the tape device file. This option is useful when you use more than one tape device.
Prerequisites
-
You have installed the
mt-st
package. For more information, see Installing tape drive management tool. Load the tape drive:
# mt -f /dev/st0 load
Procedure
Check the tape head:
# mt -f /dev/st0 status SCSI 2 tape drive: File number=-1, block number=-1, partition=0. Tape block size 0 bytes. Density code 0x0 (default). Soft error count since last status=0 General status bits on (50000): DR_OPEN IM_REP_EN
Here:
-
the current
file number
is -1. -
the
block number
defines the tape head. By default, it is set to -1. -
the
block size
0 indicates that the tape device does not have a fixed block size. -
the
Soft error count
indicates the number of encountered errors after executing the mt status command. -
the
General status bits
explains the stats of the tape device. -
DR_OPEN
indicates that the door is open and the tape device is empty.IM_REP_EN
is the immediate report mode.
-
the current
If the tape device is not empty, overwrite it:
# tar -czf /dev/st0 _/source/directory
This command overwrites the data on a tape device with the content of
/source/directory
.Back up the
/source/directory
to the tape device:# tar -czf /dev/st0 _/source/directory tar: Removing leading `/' from member names /source/directory /source/directory/man_db.conf /source/directory/DIR_COLORS /source/directory/rsyslog.conf [...]
View the status of the tape device:
# mt -f /dev/st0 status
Verification
View the list of all files on the tape device:
# tar -tzf /dev/st0 /source/directory/ /source/directory/man_db.conf /source/directory/DIR_COLORS /source/directory/rsyslog.conf [...]
Additional resources
-
mt(1)
,st(4)
, andtar(1)
man pages on your system - Tape drive media detected as write protected (Red Hat Knowledgebase)
- How to check if tape drives are detected in the system (Red Hat Knowledgebase)
17.5. Writing to non-rewinding tape devices
A non-rewinding tape device leaves the tape in its current status, after completing the execution of a certain command. For example, after a backup, you could append more data to a non-rewinding tape device. You can also use it to avoid any unexpected rewinds.
Prerequisites
-
You have installed the
mt-st
package. For more information, see Installing tape drive management tool. Load the tape drive:
# mt -f /dev/nst0 load
Procedure
Check the tape head of the non-rewinding tape device
/dev/nst0
:# mt -f /dev/nst0 status
Specify the pointer at the head or at the end of the tape:
# mt -f /dev/nst0 rewind
Append the data on the tape device:
# mt -f /dev/nst0 eod # tar -czf /dev/nst0 /source/directory/
Back up the
/source/directory/
to the tape device:# tar -czf /dev/nst0 /source/directory/ tar: Removing leading `/' from member names /source/directory/ /source/directory/man_db.conf /source/directory/DIR_COLORS /source/directory/rsyslog.conf [...]
View the status of the tape device:
# mt -f /dev/nst0 status
Verification
View the list of all files on the tape device:
# tar -tzf /dev/nst0 /source/directory/ /source/directory/man_db.conf /source/directory/DIR_COLORS /source/directory/rsyslog.conf [...]
Additional resources
-
mt(1)
,st(4)
, andtar(1)
man pages on your system - Tape drive media detected as write protected (Red Hat Knowledgebase)
- How to check if tape drives are detected in the system (Red Hat Knowledgebase)
17.6. Switching tape head in tape devices
You can switch the tape head in the tape device by using the eod
option.
Prerequisites
-
You have installed the
mt-st
package. For more information, see Installing tape drive management tool. - Data is written to the tape device. Fore more information, see Writing to rewinding tape devices or Writing to non-rewinding tape devices.
Procedure
To view the current position of the tape pointer:
# mt -f /dev/nst0 tell
To switch the tape head, while appending the data to the tape devices:
# mt -f /dev/nst0 eod
To go to the previous record:
# mt -f /dev/nst0 bsfm 1
To go to the forward record:
# mt -f /dev/nst0 fsf 1
Additional resources
-
mt(1)
man page on your system
17.7. Restoring data from tape devices
You can restore data from a tape device by using the tar
command.
Prerequisites
-
You have installed the
mt-st
package. For more information, see Installing tape drive management tool. - Data is written to the tape device. For more information, see Writing to rewinding tape devices or Writing to non-rewinding tape devices.
Procedure
For rewinding tape devices
/dev/st0
:Restore the
/source/directory/
:# tar -xzf /dev/st0 /source/directory/
For non-rewinding tape devices
/dev/nst0
:Rewind the tape device:
# mt -f /dev/nst0 rewind
Restore the
etc
directory:# tar -xzf /dev/nst0 /source/directory/
Additional resources
-
mt(1)
andtar(1)
man pages on your system
17.8. Erasing data from tape devices
You can erase data from a tape device by using the erase
option.
Prerequisites
-
You have installed the
mt-st
package. For more information, see Installing tape drive management tool. - Data is written to the tape device. For more information, see Writing to rewinding tape devices or Writing to non-rewinding tape devices.
Procedure
Erase data from the tape device:
# mt -f /dev/st0 erase
Unload the tape device:
# mt -f /dev/st0 offline
Additional resources
-
mt(1)
man page on your system