Chapter 22. Managing tape devices
Chapter 22. 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. 22.1. 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. 22.2. 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: Additional resources mt(1) and st(4) man pages on your system 22.3. Tape commands The following are the common mt commands: Table 22.1. mt commands Command Description 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 record. mt -f /dev/ nst0 eod Switches the tape head to the end of the data. 22.4. 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: Procedure Check the tape head: 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. If the tape device is not empty, overwrite it: This command overwrites the data on a tape device with the content of /source/directory . Back up the /source/directory to the tape device: View the status of the tape device: Verification View the list of all files on the tape device: Additional resources mt(1) , st(4) , and tar(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) 22.5. 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: Procedure Check the tape head of the non-rewinding tape device /dev/nst0 : Specify the pointer at the head or at the end of the tape: Append the data on the tape device: Back up the /source/directory / to the tape device: View the status of the tape device: Verification View the list of all files on the tape device: Additional resources mt(1) , st(4) , and tar(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) 22.6. 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: To switch the tape head, while appending the data to the tape devices: To go to the record: To go to the forward record: Additional resources mt(1) man page on your system 22.7. 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 / : For non-rewinding tape devices /dev/nst0 : Rewind the tape device: Restore the etc directory: Additional resources mt(1) and tar(1) man pages on your system 22.8. 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: Unload the tape device: Additional resources mt(1) man page on your system
yum install mt-st mt -f /dev/st0 load 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 tar -czf /dev/st0 _/source/directory 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 [...] mt -f /dev/st0 status tar -tzf /dev/st0 /source/directory / /source/directory /man_db.conf /source/directory /DIR_COLORS /source/directory /rsyslog.conf [...] mt -f /dev/nst0 load mt -f /dev/nst0 status mt -f /dev/nst0 rewind mt -f /dev/nst0 eod tar -czf /dev/nst0 /source/directory / 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 [...] mt -f /dev/nst0 status tar -tzf /dev/nst0 /source/directory / /source/directory /man_db.conf /source/directory /DIR_COLORS /source/directory /rsyslog.conf [...] mt -f /dev/nst0 tell mt -f /dev/nst0 eod mt -f /dev/nst0 bsfm 1 mt -f /dev/nst0 fsf 1 tar -xzf /dev/st0 /source/directory / mt -f /dev/nst0 rewind tar -xzf /dev/nst0 /source/directory / mt -f /dev/st0 erase mt -f /dev/st0 offline