How do I find out which process is preventing a umount?
When I do
sudo umount /media/KINGSTON
umount: /media/KINGSTON: device is busy.
I close all the windows and make sure all shell are pointing to other directories. How can I find which process is preventing the umount?
open a terminal:
fuser -c /media/KINGSTON
It will output something like this:
/media/KINGSTON/: 3106c 11086
This will give you the pid of the processes using this volume. The extra character at the end of pid will give some extra info. ( c in 3106c)
c – the process is using the file as its current working directory
m – the file is mapped with mmap
o – the process is using it as an open file
r – the file is the root directory of the process
t – the process is accessing the file as a text file
y – this file is the controlling terminal for the process
So to unmount just kill that pids and re-try the unmount
sudo kill -9 3106 11086 sudo umount /media/KINGSTON
Note: To find the exact application name of these pids you may use this command
For example :
this will output something like below.
Hope this will help
Also this can help:
lsof | grep /media/KINGSTON
The most useful tool is lsof . It shows what files are in used by what processes. If
/media/KINGSTON is a mount point (the device name would also work), the following command shows all files that are in use on this mount point:
If you run this command as an ordinary user, it will only show your own processes¹. Run
sudo lsof /media/KINGSTON to see all users’ processes.
The output from
lsof looks like this:
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME zsh4 31421 gilles cwd DIR 8,1 4096 130498 /var/tmp zsh4 31421 gilles txt REG 8,1 550804 821292 /bin/zsh4 zsh4 31421 gilles mem REG 8,1 55176 821326 /usr/lib/zsh/4.3.10/zsh/complist.so zsh4 31421 gilles 12r REG 8,1 175224 822276 /usr/share/zsh/functions/Completion.zwc
COMMAND column shows the name of the program executable and the
PID column shows the process ID. The
NAME column shows the file name; you might see
(deleted) if the file was deleted while open (when a file is deleted, it no longer has a name, but it still exists until the last process using it closes the file).
USER should be self-explanatory. The other columns don’t matter here except perhaps
FD, which shows how the file is used by the process:
cwd: current working directory
txt: the program executable²
mem: a memory-mapped file (here, think of it as an open file)
- a number: an actual open file; a subsequent letter indicates the opening mode, such as
rfor reading and
There is no mechanical way to locate the window where a file is open (this is in fact not technically meaningful: if a process has several windows, a file is not particularly associated with one window or another), nor even any simple way of identifying a process’s window (and of course a process doesn’t have to have any windows). But usually the command name and file name are enough to locate the offender and close the file properly.
If you can’t close the file and just want to end it all, you can kill the process with
kill 31421 (where
31421 is the process ID) or
kill -HUP 31421 (“hang up”). If plain killing doesn’t do the trick, kill with extreme prejudice:
kill -KILL 31421.
There is a GUI for lsof, glsof, but it’s not quite ready for prime time yet, and isn’t packaged for Ubuntu so far.
Lsof can list some information about other users’s processes, but it doesn’t detect the mount point so won’t list them if you specify a mount point.
Executable code is often called text in discussions of executable formats.
Meanwhile the fuser command has much improved. You can do the full job with a single command:
$ sudo fuser -ickv /"mountpoint"
kkills the offending process,
vshows in advance the process and its user
iasks you for confirmation.
If some process resists, then try again with
fuser -ickv -9 (or more generally with
-SIGNAL) that kills the most stubborn ones.
But you will always find some “immortal” process…!
In this cases I lately learned to use
$ sudo umount --lazy --force <mountpoint>
as a last resource, that up to now worked for me every time.
Note! One other thing that keeps a mountpoint busy is a submount, which isn’t a process so won’t show up if you search via
fuser. And yes, it should be obvious,but in this age of a long list of mounts due to docker and rebinds and etc, it can be easy to overlook that, for instance:
# mount | wc -l 39 # mount |grep usb /dev/sde1 on /media/usb type vfat (rw,relatime,fmask=0022,dmask=0022,codepage=437,iocharset=utf8,shortname=mixed,errors=remount-ro) /media/usb/boot/modloop-lts on /.modloop type squashfs (ro,relatime)
/media/usb cannot be unmounted because of the second mount. (example taken from a real-life alpine linux "diskless" system where I just spent around 10min trying to figure out why I couldn’t unmount /media/usb)