Why can’t I remove a Linux logical volume?

If you are unable to unmount or lvremove a logical volume, verify that there are no processes holding the LV.

Locate the major/minor numbers for the logical volume you’re trying to remove (ie lvol0):

dmsetup info -c | grep lvol0

Take note of the 5th column, which indicates if a volume is “open,” and the 2nd and 3rd columns, which are the major and minor IDs, respectively. For example:

[root@eclipse ~]# dmsetup info -c | grep lvol5
datavg-lvol5         253  24 L--w    1    1      0 LVM-4WlscxDDEw5R9IvjgZYpu5FQeW9h835ADtQzXFr3cJ6SHEcgS4NFMxzaSKjUkedy
datavg-lvol5-cow     253  27 L--w    1    2      0 LVM-4WlscxDDEw5R9IvjgZYpu5FQeW9h835ADtQzXFr3cJ6SHEcgS4NFMxzaSKjUkedy-cow

Find any process attached to this volume by searching on the major and minor IDs discovered above:

lsof | grep "major,minor"

For example:

[root@eclipse ~]# lsof | grep "253,24"
beremote  14524      root   15r      BLK             253,24                1835186 /tmp/filehRrCD8 (deleted)

Shut down or kill any process still accessing the volume to continue unmounting and removal.

If no processes show as accessing the volume in lsof, check to make sure nothing is sharing the filesystem (i.e. rsync, nfs, or samba).

If you have verified that no processes are holding the LV open, verify that the LV is not mounted somewhere:

cat /proc/mounts

If the volume appears in the output, unmount it using the umount command.
For further assistance, please contact Red Hat for support

How do I troubleshoot tape backups on Linux?

Here are a few helpful procedures for troubleshooting tape backup problems under Linux.

  • First, test the tape drive by attempting to rewind the tape:
mt -f /dev/st0 rewind
    • If there are no problems issuing the rewind command, you’ll be returned to the command prompt.
    • If there are any issues, you will be presented with a descriptive error message.
  • Next, try to perform a manual backup of a few small files:
tar -czvpf /dev/st0 /etc
    • If there are no problems performing the test backup, you’ll see a number of files scroll by and then be returned to the command prompt.
    • If there are any issues, you will presented with a descriptive error message.
  • If there were errors with either of the above tests, please run the Dell Hardware diagnostics

Here are some common errors you may see with tape drives under Linux:

  • Tape has been marked as write-protected or read-only:
tar: /dev/st0: Cannot open: Read-only file system
tar: Error is not recoverable: exiting now

Resources:

How do I troubleshoot a Linux printer

To troubleshoot a print queue on Linux:

  • Log into the server as root
  • Try to ping the server:
ping -c4 lp1
  • Common problems:
    • If the printer doesn’t respond, verify its network connectivity
    • If the printer exhibits packet loss or high latency (round trip) times, check with your network support provider, as these can disrupt printing
  • Check the Linux (CUPS) print queue status:
lpstat -p lp1
  • Common problems:
    • If the printer is “disabled” or “paused,” enable the queue: cupsenable lp1
  • Check the UniVerse (UV) print queue status:
usa -p lp1
  • Common problems:
    • If the printer is marked as “off,” enable the queue: usa +o -p lp1