I recently switched to CentOS 7. I was trying to safely remove my backup drive. The drive unmounts, but the LED on it, stays on.

I know how a disk can be safely removed using command line as answered here. So I issued the following commands

udisksctl unmount -b /dev/sdb1
udisksctl power-off -b /dev/sdb

(yes my disk was /dev/sdb) Which outputs the following :

Unmounted /dev/sdb1.
Unknown command `power-off'
  udisksctl COMMAND

  help            Shows this information
  info            Shows information about an object
  dump            Shows information about all objects
  status          Shows high-level status
  monitor         Monitor changes to objects
  mount           Mount a filesystem
  unmount         Unmount a filesystem
  unlock          Unlock an encrypted device
  lock            Lock an encrypted device
  loop-setup      Set-up a loop device
  loop-delete     Delete a loop device
  smart-simulate  Set SMART data for a drive

Use "udisksctl COMMAND --help" to get help on each command.

I checked if I was using the latest version of udisks2:

sudo yum install udisks2
[sudo] password for user: 
Loaded plugins: langpacks
Loading mirror speeds from cached hostfile
 * base: centos.excellmedia.net
 * extras: centos.excellmedia.net
 * rpmfusion-free-updates: fr2.rpmfind.net
 * rpmfusion-nonfree-updates: fr2.rpmfind.net
 * updates: centos.excellmedia.net

Package udisks2-2.1.2-6.el7.x86_64 already installed and latest version
Nothing to do

I have thoroughly searched the web, but nothing relevant showed up. I think I could be missing a package, because I did a minimal install, though I am not certain if that is the case. Can someone please help me out?

1 Answer 1


The power-off command was added 4 years ago. According to the NEWS file, it is available from version 2.1.3. You have version 2.1.2.

When checking for updates, you get the latest version for your distribution. That’s not necessarily the latest version available directly from the developers.


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