15 Useful Linux and Unix Tape Managements Commands For Sysadmins - nixCraft

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15 Useful Linux and Unix Tape
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Managements Commands For
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Sysadmins
Author: Vivek Gite • Last updated: December 22, 2020 • 5 comments
T
ape devices should be used on a regular basis only for archiving Cles or for
transferring data from one server to another. Usually, tape devices are all
hooked up to Unix boxes, and controlled with mt or mtx. You must backup all
data to both disks (may be in the cloud) and the tape device. In this tutorial you
will learn about:
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SysAdmin Should Know
Tape device names
Basic commands to manage tape drive
Basic backup and restore commands
Why do you need backups?
For New SysAdmins
A backup plan is necessary for you to backup your Cles on a regular basis. If you
choose not to back up your own Cles, you risk losing important data. A backup
Practices
allows you to:
Ability to recover from disk failure
Practices
Accidental Cle deletion
File or Cle system corruption
Complete server destruction, including the destruction of on-site backups
due to Cre or other problems
Hard drives and SSD do crash
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Viruses and ransomware can corrupt or delete Cles
You can use tape-based archives to backup the whole server and move tapes
off-site.
Understanding tape Cle marks and block size
/etc
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Fig.01: Tape Cle marks
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Each tape device can store multiple tape backup Cles. Tape backup Cles are
created using cpio, tar, dd, and so on. However, tape device can be opened,
written data to, and closed by the various program. You can store several
backups (tapes) on physical tape. Between each tape Cle is a “tape Cle mark”.
This is used to indicate where one tape Cle ends and another begins on physical
tape. You need to use mt command to positions the tape (winds forward and
rewinds and marks).
How is data stored on a tape drive
Fig.02: How data is stored on a tape
All data is stored subsequently in sequential tape archive format using tar. The
Crst tape archive will start on the physical beginning of the tape (tar #0). The
next will be tar #1 and so on.
Tape device names on Unix
1. /dev/rmt/0 or /dev/rmt/1 or /dev/rmt/[0-127] : Regular tape device name on
Unix. The tape is rewound.
2. /dev/rmt/0n : This is know as no rewind i.e. after using tape, leaves the tape
in current status for next command.
3. /dev/rmt/0b : Use magtape interface i.e. BSD behavior. More-readable by a
variety of OS’s such as AIX, Windows, Linux, FreeBSD, and more.
4. /dev/rmt/0l : Set density to low.
5. /dev/rmt/0m : Set density to medium.
g. /dev/rmt/0u : Set density to high.
7. /dev/rmt/0c : Set density to compressed.
h. /dev/st[0-9] : Linux speciCc SCSI tape device name.
9. /dev/sa[0-9] : FreeBSD speciCc SCSI tape device name.
10. /dev/esa0 : FreeBSD speciCc SCSI tape device name that eject on close (if
capable).
Tape device name examples
The
indicate that I’m using unity 1, compressed density and
/dev/rmt/1cn
no rewind.
The
indicate that I’m using unity 0, high density and BSD
/dev/rmt/0hb
behavior.
The auto rewind SCSI tape device name on Linux : /dev/st0
The non-rewind SCSI tape device name on Linux : /dev/nst0
The auto rewind SCSI tape device name on FreeBSD: /dev/sa0
The non-rewind SCSI tape device name on FreeBSD: /dev/nsa0
How do I list installed SCSI tape devices?
Type the following commands:
## Linux (read man pages for more info) ##
lsscsi
lsscsi -g
## IBM AIX ##
lsdev -Cc tape
lsdev -Cc adsm
lscfg -vl rmt*
*
## Solaris Unix ##
cfgadm –a
cfgadm -al
luxadm probe
iostat -En
## HP-UX Unix ##
ioscan Cf
ioscan -funC tape
ioscan -fnC tape
ioscan -kfC tape
Sample outputs from my Linux server:
Fig.03: Installed tape devices on Linux server
mt command examples
In Linux and Unix-like system, the mt command is used to control operations of
the tape drive, such as Cnding status or seeking through Cles on a tape or writing
tape control marks to the tape. You must type the following command as root
user. The syntax is:
mt -f / tape/
/device/
/name operation
Setting up environment
You can set
shell variable. This is the pathname of the tape drive. The
TAPE
default (if the variable is unset, but not if it is null) is /dev/nsa0 on FreeBSD. It
may be overridden with the
option passed to the
-f
mt
command as
explained below.
## Add to your shell startup file ##
TAPE=/
/dev/
/st1 #Linux
TAPE=/
/dev/
/rmt/
/2 #Unix
TAPE=/
/dev/
/nsa3 #FreeBSD
export TAPE
1: Display status of the tape/drive
#Use default
mt status
mt -f / dev/
/rmt/
/0
status #Unix
mt -f / dev/
/st0 status #Linux
mt -f / dev/
/nsa0 status #FreeBSD
mt -f / dev/
/rmt/
/1 status #Unix unity 1 i.e. tape device no. 1
You can use shell loop as follows to poll a system and locate all of its tape
drives:
for d in 0 1 2 3 4 5
do
mt -f "/dev/rmt/${d}" status
done
2: Rewinds the tape
mt rew
mt rewind
mt -f / dev/
/mt/
/0 rewind
mt -f / dev/
/st0 rewind
3: Eject the tape
mt off
mt offline
mt eject
mt -f / dev/
/mt/
/0 off
mt -f / dev/
/st0 eject
4: Erase the tape (rewind the tape and, if
applicable, unload the tape)
mt erase
mt -f / dev/
/st0 erase
#Linux
mt -f / dev/
/rmt/
/0 erase #Unix
5: Retensioning a magnetic tape cartridge
If errors occur when a tape is being read, you can retension the tape, clean the
tape drive, and then try again as follows:
mt retension
mt -f / dev/
/rmt/
/1 retension #Unix
mt -f / dev/
/st0 retension #Linux
6: Writes n EOF marks in the current position of
tape
mt eof
mt weof
mt -f / dev/
/st0 eof
7: Forward space count Cles i.e. jumps n EOF
marks
The tape is positioned on the Crst block of the next Cle i.e. tape will position on
Crst block of the Celd (see Cg.01):
mt fsf
mt -f / dev/
/rmt/
/0 fsf
mt -f / dev/
/rmt/
/1 fsf 1 #go 1 forward file/tape (see fig.01)
8: Backward space count Cles i.e. rewinds n EOF
marks
The tape is positioned on the Crst block of the next Cle i.e. tape positions after
EOF mark (see Cg.01):
mt bsf
mt -f / dev/
/rmt/
/1 bsf
mt -f / dev/
/rmt/
/1 bsf 1 #go 1 backward file/tape (see fig.01)
Here is a list of the tape position commands:
fsf
Forward space count files.
The tape is positioned on the first block of the next file.
fsfm
Forward space count files.
The tape is positioned on the last block of the previous file.
bsf
Backward space count files.
The tape is positioned on the last block of the previous file.
bsfm
Backward space count files.
The tape is positioned on the first block of the next file.
asf
The tape is positioned at the beginning of the count file. Positioning is done by first rewinding the tape and then spacing forward over count filemarks.
fsr
Forward space count records.
bsr
Backward space count records.
fss
( SCSI tapes)
) Forward space count setmarks.
bss
( SCSI tapes)
) Backward space count setmarks.
Basic backup commands
Let us see commands to backup and restore Cles
9: To backup directory (tar format)
tar cvf / dev/
/rmt/
/0n / etc
tar cvf / dev/
/st0 / etc
10: To restore directory (tar format)
tar xvf / dev/
/rmt/
/0n -C / path/
/to/
/restore
tar xvf / dev/
/st0 -C / tmp
11: List or check tape contents (tar format)
mt -f / dev/
/st0 rewind; dd if=/
/dev/
/st0 of=-
## tar format ##
tar tvf { DEVICE}
} { Directory-FileName}
}
tar tvf / dev/
/st0
tar tvf / dev/
/st0 desktop
tar tvf / dev/
/rmt/
/0 foo > list.txt
12: Backup partition with dump or ufsdump
## Unix backup c0t0d0s2 partition ##
ufsdump 0uf / dev/
/rmt/
/0
/ dev/
/rdsk/
/c0t0d0s2
## Linux backup /home partition ##
dump 0uf / dev/
/nst0 / dev/
/sda5
dump 0uf / dev/
/nst0 / home
## FreeBSD backup /usr partition ##
dump -0aL -b64 -f / dev/
/nsa0 / usr
12: Restore partition with ufsrestore or restore
## Unix ##
ufsrestore xf / dev/
/rmt/
/0
## Unix interactive restore ##
ufsrestore if / dev/
/rmt/
/0
## Linux ##
restore rf / dev/
/nst0
## Restore interactive from the 6th backup on the tape media ##
restore isf 6 / dev/
/nst0
## FreeBSD restore ufsdump format ##
restore -i -f / dev/
/nsa0
13: Start writing at the beginning of the tape (see
Cg.02)
## This will overwrite all data on tape ##
mt -f / dev/
/st1 rewind
### Backup home ##
tar cvf / dev/
/st1 / home
## Offline and unload tape ##
mt -f / dev/
/st0 offline
To restore from the beginning of the tape:
mt -f / dev/
/st0 rewind
tar xvf / dev/
/st0
mt -f / dev/
/st0 offline
14: Start writing after the last tar (see Cg.02)
## This will kee all data written so far ##
mt -f / dev/
/st1 eom
### Backup home ##
tar cvf / dev/
/st1 / home
## Unload ##
mt -f / dev/
/st0 offline
15: Start writing after tar number 2 (see Cg.02)
## To wrtite after tar number 2 (should be 2+1)
mt -f / dev/
/st0 asf 3
tar cvf / dev/
/st0 / usr
## asf equivalent command done using fsf ##
mt -f / dev/
/sf0 rewind
mt -f / dev/
/st0 fsf 2
To restore tar from tar number 2:
mt -f / dev/
/st0 asf 3
tar xvf / dev/
/st0
mt -f / dev/
/st0 offline
How do I verify backup tapes created using tar?
It is important that you do regular full system restorations and service testing, it’s
the only way to know for sure that the entire system is working correctly. See our
tutorial on verifying tar command tape backups for more information.
Sample shell script
#!/bin/bash
# A UNIX / Linux shell script to backup dirs to tape device like /dev/st0 (linux)
# This script make both full and incremental backups.
# You need at two sets of five
tapes. Label each tape as Mon, Tue, Wed, Thu and Fri.
# You can run script at midnight or early morning each day using cronjons.
# The operator or sys admin can replace the tape every day after the script has done.
# Script must run as root or configure permission via sudo.
# ------------------------------------------------------------------------# Copyright (c) 1999 Vivek Gite <vivek@nixcraft.com>
# This script is licensed under GNU GPL version 2.0 or above
# ------------------------------------------------------------------------# This script is part of nixCraft shell script collection (NSSC)
# Visit https://bash.cyberciti.biz/ for more information.
# ------------------------------------------------------------------------# Last updated on : March-2003 - Added log file support.
# Last updated on : Feb-2007 - Added support for excluding files / dirs.
# ------------------------------------------------------------------------LOGBASE=/
/root/
/backup/
/log
# Backup dirs; do not prefix /
BACKUP_ROOT_DIR="home sales"
# Get todays day like Mon, Tue and so on
NOW=$(
(date +"%a")
)
# Tape devie name
TAPE="/dev/st0"
# Exclude file
TAR_ARGS=""
EXCLUDE_CONF=/
/root/
/.backup.exclude.conf
# Backup Log file
LOGFIILE=$LOGBASE/
/$NOW.backup.log
# Path to binaries
TAR=/
/bin/
/tar
MT=/
/bin/
/mt
MKDIR=/
/bin/
/mkdir
# -----------------------------------------------------------------------# Excluding files when using tar
# Create a file called $EXCLUDE_CONF using a text editor
# Add files matching patterns such as follows (regex allowed):
# home/vivek/iso
# home/vivek/*.cpp~
# -----------------------------------------------------------------------[ -f $EXCLUDE_CONF ] && TAR_ARGS="-X $EXCLUDE_CONF"
#### Custom functions #####
# Make a full backup
full_backup(
() {
local old=$(
(pwd
pwd)
)
cd /
$TAR $TAR_ARGS -cvpf $TAPE $BACKUP_ROOT_DIR
$MT -f $TAPE rewind
$MT -f $TAPE offline
cd $old
}
# Make a
partial backup
partial_backup(
() {
local old=$(
(pwd
pwd)
)
cd /
$TAR $TAR_ARGS -cvpf $TAPE -N "$(date -d '1 day ago')" $BACKUP_ROOT_DIR
$MT -f $TAPE rewind
$MT -f $TAPE offline
cd $old
}
# Make sure all dirs exits
verify_backup_dirs(
() {
local s=0
for d in $BACKUP_ROOT_DIR
do
if [ ! -d / $d ] ;
then
echo "Error : /$d directory does not exits!"
s=1
fi
done
# if not; just die
[ $s -eq 1 ] && exit 1
}
#### Main logic ####
# Make sure log dir exits
[ ! -d $LOGBASE ] && $MKDIR -p $LOGBASE
# Verify dirs
verify_backup_dirs
# Okay let us start backup procedure
# If it is Monday make a full backup;
# For Tue to Fri make a partial backup
# Weekend no backups
case $NOW in
Mon)
)
full_backup;;
;;
Tue|
|Wed|
|Thu|
|Fri)
)
partial_backup;;
;;
* ) ;;
esac > $LOGFIILE 2>&
>&1
A note about third party backup utilities
Both Linux and Unix-like system provides many third-party utilities which you can
use to schedule the creation of backups including tape backups such as:
Amanda
Bacula
rsync
duplicity
rsnapshot
See also
Man pages –
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5 comments… add one ↓
Ronny Mandal • Mar 28, 2016 @ 9:46
I really like the concept of storing data on data. I have a HP DAT 160-station and
a lot of tapes. The problem is, the capacity of one tape is 80 GB uncompressed.
My RAID-volume is 21 TB.
↩
∞
Egil Simones • Dec 21, 2020 @ 14:18
Hi Ronny,
we supply tapedrives now with 20TB native capacity. IBM 3592’s. Så you can
manage with quite few tapes. We can also to a library so you can mount 116000 tapes.
↩
∞
Ron Barak • May 17, 2016 @ 11:17
Erratum:
8: Backward space count Cles i.e. rewinds n EOF marks
The tape is positioned on the Crst block of the next Cle i.e. tape positions after
EOF mark
->
8: Backward space count Cles i.e. rewinds n EOF marks
The tape is positioned on the Crst block of the previous Cle i.e. tape positions
after EOF mark
↩
∞
HUssam • Dec 15, 2017 @ 13:07
Thanks for sharing the scripts and information.
Can we alter a tape track without ruining all data tracks that follow?
I have been working with dozens of LTO drives from different vendors and
ranging for LTO2 to LTO5, and they all share the same behavior: when a track is
written, double Clemarks (EOFs) are written at the end marking not only the end
of the track but also the end of data. So if I wanted to change data in a tack in
the middle of the tape (retaining track size of course) I would not be able to do it
without killing the following tracks. Looking into st driver man page, there is a
driver yag MT_ST_TWO_FM that describes this behavior and the default is off.
Looking at drive options under /sys/class/scsi_tape/ conCrms that this yag is
off, however, the behavior is happening.
I think there are two possible explanations, either st driver compatibility issue
with LTO drives, or this is a default behavior implemented in drive’s hardware
ignoring the st driver’s yag.
Any thoughts or workarounds?
↩
∞
Egil Simones • Dec 21, 2020 @ 14:20
Hi,
you can ust LTFS, Linear Tape File System, which make your tape like a disk.
That is free and supported for lto and 3592 for Linux and Windows.
Egil Simones, Eurotech Norway
↩
∞
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