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Today, let us see how to resolve this error.

Remove ioctl failed: Device or resource busy

Let us go through the steps followed by our Support Techs to find the process preventing the dm entry from removed:

1.Firstly, SSH into HV shown in the error log.

2.Then, check the device mapper hierarchy to see which backup is utilizing the -real snapshot in the error log.

Run the below command:

dmsetup ls –tree | grep -B5 onapp–xxxxxxxxxxxxxx-zzzzzzzzzzzzzz-real

Please note if you don’t see the root backup device, you may need to increase the value for the -B switch to something higher than 5.

3.Then, determine what process is using the top dm entry in the hierarchy with lsof.

onapp–xxxxxxxxxxxxxx-backup–yyyyyyyyyyyyyy

Run the below command:

lsof /dev/onapp-xxxxxxxxxxxxxx/backup-yyyyyyyyyyyyyy

4.Since the backup is being utilized by tgtd, check if there are any iSCSI targets active.

Run the below command:

tgtadm –lld iscsi –mode target –op show

5.Then, check the Backup Server for related ISCSI sessions and logout of them.

• Login to the backup server shown under “ACL information” from the previous step and run iscsiadm -m session.
• Compare the target name from the previous step and logout of the corresponding ISCSI sessions using iscsiadm -m node -u -T <target name>.
• If there are no corresponding sessions on the backup server, you can skip to step 6.

Make sure the -T command is -T. If the iscsiadm command does not receive the -T after the -u, it will logout of all iscsi targets.

6.Delete the iSCSI target.

• Go back to the Hypervisor and run tgtadm –lld iscsi –op delete –mode target –tid *
• tid stands for Target ID, which is shown when running the command in step 4.

7.Finally, remove the dm entries for the backup and the -real snapshot.

For entries that end with X1, you should run this first:

kpartx -d -p X /dev/mapper/backup-XXXXXXXXXX

Then, run the below commands:

dmsetup remove /dev/onapp-xxxxxxxxxxxxxx/backup-yyyyyyyyyyyyyy

dmsetup remove /dev/onapp-xxxxxxxxxxxxxx/backup-yyyyyyyyyyyyyy-cow

dmsetup remove /dev/mapper/onapp–xxxxxxxxxxxxxx-zzzzzzzzzzzzzz-real

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Conclusion

In short, we saw steps followed by our Support Techs to find the process preventing the dm entry from removed