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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
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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
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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
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17.3. Tape commands
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The following are the common mt commands:

Expand
Table 17.1. mt commands
CommandDescription

mt -f /dev/st0 status

Displays the status of the tape device.

mt -f /dev/st0 erase

Erases the entire tape.

mt -f /dev/nst0 rewind

Rewinds the tape device.

mt -f /dev/nst0 fsf n

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.

mt -f /dev/nst0 bsfm n

Switches the tape head to the previous record.

mt -f /dev/nst0 eod

Switches the tape head to the end of the data.

17.4. Writing to rewinding tape devices
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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

  1. You have installed the mt-st package. For more information, see Installing tape drive management tool.

  2. Load the tape drive: 

    # mt -f /dev/st0 load
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Procedure

  1. 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
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    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.

  2. If the tape device is not empty, overwrite it: 

    # tar -czf /dev/st0 _/source/directory
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    This command overwrites the data on a tape device with the content of /source/directory.

  3. 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
[...]
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  4. View the status of the tape device: 

    # mt -f /dev/st0 status
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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
[...]
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17.5. Writing to non-rewinding tape devices
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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

  1. You have installed the mt-st package. For more information, see Installing tape drive management tool.

  2. Load the tape drive: 

    # mt -f /dev/nst0 load
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Procedure

  1. Check the tape head of the non-rewinding tape device /dev/nst0: 

    # mt -f /dev/nst0 status
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  2. Specify the pointer at the head or at the end of the tape: 

    # mt -f /dev/nst0 rewind
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  3. Append the data on the tape device: 

    # mt -f /dev/nst0 eod
# tar -czf /dev/nst0 /source/directory/
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  4. 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
[...]
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  5. View the status of the tape device: 

    # mt -f /dev/nst0 status
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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
[...]
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17.6. Switching tape head in tape devices
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You can switch the tape head in the tape device by using the eod option.

Prerequisites

  1. You have installed the mt-st package. For more information, see Installing tape drive management tool.
  2. 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
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  • To switch the tape head, while appending the data to the tape devices: 

    # mt -f /dev/nst0 eod
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  • To go to the previous record: 

    # mt -f /dev/nst0 bsfm 1
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  • To go to the forward record: 

    # mt -f /dev/nst0 fsf 1
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17.7. Restoring data from tape devices
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You can restore data from a tape device by using the tar command.

Prerequisites

  1. You have installed the mt-st package. For more information, see Installing tape drive management tool.
  2. 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/
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  • For non-rewinding tape devices /dev/nst0:

    • Rewind the tape device: 

      # mt -f /dev/nst0 rewind
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    • Restore the etc directory: 

      # tar -xzf /dev/nst0 /source/directory/
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17.8. Erasing data from tape devices
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You can erase data from a tape device by using the erase option.

Prerequisites

  1. You have installed the mt-st package. For more information, see Installing tape drive management tool.
  2. Data is written to the tape device. For more information, see Writing to rewinding tape devices or Writing to non-rewinding tape devices.

Procedure

  1. Erase data from the tape device: 

    # mt -f /dev/st0 erase
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  2. Unload the tape device: 

    # mt -f /dev/st0 offline
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