I have a tape drive that attached to the Redhat server , I use dmesg show the below messages

#dmesg |grep tape
Attached scsi tape st0 at scsi1, channel 0, id 5, lun 0
st0: Write not multiple of tape block size.

I assume the drive is attached to the device path /dev/st0 of my server , then I tried tar -cvf /dev/st0 /tmp , but I found that the file is backup to the file /dev/st0 but not the tape drive , can advise how can I know what device path that attached ? thx

hwinfo --tape
will show you the device file, e.g. /dev/tape or /dev/st0, and the driver the system tries to use. then
mt -f <devic file> status
will show you the state of your tape device.

If it wrote to a file it suggests that the "device" files were not created for your drive.

If you do something like "ls -l /dev/st0*" you ought to see something like:
crw-rw---- 1 root disk 9, 0 Apr 12 22:12 /dev/st0
crw-rw---- 1 root disk 9, 96 Apr 12 22:12 /dev/st0a
crw-rw---- 1 root disk 9, 32 Apr 12 22:12 /dev/st0l
crw-rw---- 1 root disk 9, 64 Apr 12 22:12 /dev/st0m

The c in first position tells you that you have a character (a/k/a raw) device file. If there is no c (or b, l, or d) then it is is a "regular" file. You should delete that regular file then run:

That should make the device files for you.

thx reply,

I can eject the tape by mt -f /dev/st0 offline , the device path /dev/st0 must is my tape device , but when tar file to it "tar -zcvf /dev/st0 file" , I found there is a file /dev/st0 created , it seems not write to the tape , can advise what is wrong ? thx

It doesn't make sense that mt would find the device file by name but your tar wouldn't.

Type "ls -l /dev/st0*" and post results here please.

crw-rw---- 1 root disk 9, 0 Jun 24 2004 /dev/st0
crw-rw---- 1 root disk 9, 96 Jun 24 2004 /dev/st0a
crw-rw---- 1 root disk 9, 32 Jun 24 2004 /dev/st0l
crw-rw---- 1 root disk 9, 64 Jun 24 2004 /dev/st0m

please write to the tape "tar -cf /dev/st0 <some_files>" then "ls -l /dev/st0*" then "tar -tf /dev/st0" and post all the output.

You have: crw-rw---- 1 root disk 9, 0 Jun 24 2004 /dev/st0

That is the character device file you should have so I don't understand why you think it is "creating a file" rather than writing to tape. That character device file IS the tape drive not a regular file.

thx replies,

I still can't find it

dev]# ls -l /dev/st0
ls: /dev/st0: No such file or directory

After tar -cf /dev/st0 <some_files> , /dev/st0 is a file , the file not begins with c ,


Thx

I will reboot it later for creating /dev/st0 .

But I am wonder in my system , there is /nst0 , is it also the tape drive path ? if yes , why I am unable to write files to the tape ?
#ll /dev/nst0
crw-rw---- 1 root disk 9, 128 Jun 25 2004/dev/nst0



#tar -cvf /dev/nst0 /tmp/*
/tmp/file.txt
tar (child): /dev/nst0: Wrote only 0 of 10240 bytes
tar (child): Error is not recoverable: exiting now
Broken pipe

/dev/nst0 should point to same drive as /dev/st0. The difference being that the /dev/st0 will automatically rewind tape after the backup and the /dev/nst0 won't. (The n = "no rewind".) The reason for using a no rewind device is to allow you to add another backup after the one already on the tape.

I just noticed something though - In an earlier post you put as output for "ls -l /dev/st0*" the following:

However you just posted:
In the earlier post you see /dev/st0 but in later one you don't. This could occur if in fact the file that appears to be /dev/st0 in earlier post has hidden characters after the name. Sometimes you could see this by trying to type "ls -l /dev/st0* |cat -v".

Alternatively you could simply do "rm /dev/st0*" then do the MAKEDEV I suggested in an earlier post. You do not need to reboot to make the devices as that is what MAKEDEV does.