badblocks: says it is not safe to run and stops

Symptoms:

When checking for bad blocks, following error is displayed:

# badblocks -nvs /dev/sdb
/dev/sdb is apparently in use by the system; it's not safe to run badblocks!

Solution:

1. Check the mounts (/etc/mtab), unmount with umount
2. Check the swaps (/proc/swaps), unmount with swapoff
3. Check volume groups (/dev/mapper/...), deactivate with vgchange -a n