Device busy when reading from tape drive with tar

When I try to read a tar from tape with tar tvbf 2048 /dev/nst0, it returns:

tar: /dev/nst0: Cannot read: Device or resource busy
tar: At beginning of tape, quitting now
tar: Error is not recoverable: exiting now

And lsof | grep st0 returns nothing.

All commands works with mt works. If I try with strace:

...
open("/dev/nst0", O_RDONLY)             = 3
read(3, 0x7ff16eb8f000, 1048576)        = -1 EBUSY (Device or resource busy)
...

The tape drive has the latest firmware. The tape drive is an IBM ULTRIUM-HH6 and the firmware is F9A1.

Solution 1:

• Did you also write with the same block size?
• Did you rewind beforereading?
• Does mt -f /dev/nst0 status work?
• Are you chaining dd with tar or just using tar as you wrote? There is a quirk when using tar piping and $TAPE environment variable. see below.

Sometimes you issue a command, it fails, there is no noise from the drive, but the tape is not in "rewound" state anymore. Try implicit rewind before each command.

Do a test with another tape (run the commands immediately after each other: cd /path/to files mt -f /dev/nst0 rewind; tar -b 2048 -c -f /dev/nst0 * mt -f /dev/nst0 rewind; tar -b 2048 -t -f /dev/nst0

Btw if you don't want to pass -f /dev/nst0 all the time add export TAPE=/dev/nst0 in your .bashrc. Keep in mind that if you have this variable tar will prefer the tape drive over stdin/stdout. So this will return "Device or resource busy"

export TAPE=/dev/nst0
mt rewind ; tar -b 128 -c *|dd of=$TAPE bs=64K 

... because both dd and tar are trying to open the tape drive. The correct way to pipe tar is by passing -f -:

mt rewind ; tar -b 128 -c -f - *|dd of=$TAPE bs=64K 

Also I'm not sure if this block size will work well. In this document you can read:

A block size no larger than 256 KB (262144 bytes) is strongly recommended when working with HP-UX and tape or VTL devices.

So try dropping the block size to 256KiB or even 128KiB (That's tar -b 512 or -b 256 respectively).