why can't I umount /home?
Emily Wong 
I'm trying to create a new partition on my Linux system, my intent is to take a small amount of my /home filesystem and change the type for experimentation. I'm using OpenSuse 12.1 in a virtual box.
gparted shows I have the following partitions:
Partition File System MountPoint Size Used
********************************************************
/dev/sda1 linux-swap 744.00MiB ---
/dev/sda2 ext4 / 10.35GiB 5.16GiB
unallocated 1.00MiB ---
/dev/sda3 ext4 /home 28.92GiB 11.51GiB
unallocated 1.00MiB ---I'm logged in a root and my cwd is /, when I try umount /home I get:
umount: /home: device is busy. (In some cases useful info about processes that use the device is found by lsof(8) or fuser(1))
When I run fuser -m /dev/sda3 I get a good sized list:1 303 311 594 649 672 692 696 700 738 754 786...
running ps -e I can find these processes:
PID TTY TIME CMD
1 ? 00:00:00 systemd
303 ? 00:00:00 systemd-stdout-
311 ? 00:00:00 udevd
594 ? 00:00:00 systemd-logind
649 ? 00:00:00 systemd-logind
672 ? 00:00:00 avahi-daemon
692 ? 00:00:00 acpid
700 ? 00:00:00 haveged
...What I'm trying to figure out is how to proceed. I guess I can "force" the umount, but that seems like a bad idea. I can kill all of these processes, then do the umount, but I'm not sure that will work.
What other options do I have? How should I unmount the /home drive?
3 Answers
You should boot into a rescue session using a Linux CD, or you can drop to a lower runlevel using init. It is not a good idea to unmount your $HOME while logged in.
You might also be able to do this if you log in as root (actually log in, not su or sudo). That way the /home partition is not needed and you will be able to unmount it. You will still have to make sure no one is accessing it (see next paragraph) and unmount it manually.
Finally, a useful tool is lsof /dev/sda3 which will list the processes currently accessing that partition. To kill all processes listed by lsof (careful, this may crash your system, depending on the process, but if this happens you should be OK after a reboot), do this:
kill `lsof /dev/sda3 | awk '{print $2}'`You have to be sure that no user is currently logged in in order to unmount a home partition. To do this you can either do that operation using a live distro, or you can try to login to your OS in console mode and login directly as root.
If you want to try this second option, you may find this question useful.
2Be sure to log out of any Vsphere client sessions to the VM. Both the standard and Web Based. Then use SSH to login with root and you should be able to umount the partition.
