Why can't I unmount /tmp ?

[Jerry_109]

Hello All,

Why can't we unmount fdhp31:/tmp ?

##################################
root@fdhp31[/root]
HP-UX fdhp31 B.11.23 U 9000/800/A500-7X
##################################
root@fdhp31[/root]
# bdf /tmp
Filesystem kbytes used avail %used Mounted on
/dev/vg00/tmp 2048000 32936 1999392 2% /tmp

root@fdhp31[/root]
# grep tmp /etc/fstab
/dev/vg00/tmp /tmp vxfs delaylog 0 2

##################################
root@fdhp31[/root]
# cat /etc/mnttab
/dev/vg00/root / vxfs ioerror=mwdisable,delaylog,dev=40000003 0 1 1199742090
/dev/vg00/stand /stand hfs defaults,dev=40000001 0 0 1199742093
/dev/vg00/usr /usr vxfs ioerror=mwdisable,delaylog,dev=40000007 0 0 1199742805
/dev/vg00/opt /opt vxfs ioerror=mwdisable,delaylog,dev=40000005 0 0 1199743217
/dev/vg00/home /home vxfs ioerror=mwdisable,delaylog,dev=40000004 0 0 1199743258
/dev/vg00/tmp /tmp vxfs ioerror=mwdisable,delaylog,dev=40000006 0 0 1199743287
/dev/vg00/var /var vxfs ioerror=mwdisable,delaylog,dev=40000008 0 0 1199743332
-hosts /net autofs ignore,indirect,nosuid,soft,nobrowse,dev=60000000 0 0 1199743522
##################################

root@fdhp31[/]
# fuser -u /dev/vg00/tmp
/dev/vg00/tmp:

root@fdhp31[/]
# umount /tmp
umount: cannot unmount /tmp : Device busy
umount: return error 1.

[Geoff Wild · Accepted solution]

Your answer is in the error:

umount: cannot unmount /tmp : Device busy


fuser -cu /tmp


/tmp is used by the OS...

Why do you need to un mount it?

Rgds...Geoff

[Jerry_109]

A co-worker was testing the umount command on a test system. I have successfully unmounted /tmp before. Just want to understand why ? I'll see if I can install lsof to gather more info ( maybe a socket ? )
Thanks.
##################################
root@fdhp31[/]
# fuser -cu /tmp
/tmp:

root@fdhp31[/]
# umount /tmp
umount: cannot unmount /tmp : Device busy
umount: return error 1.

[Mridul Shrivastava]

fuser o/p clearly shows that it is being used by root hence we can not unmount a filesystem which is still in use. This is the reason we are getting error device busy

[Geoff Wild]

Well - if fuser -cu returns nothing, then it more then likely means a process was probably killed with -9, and a file in /tmp is still considered open....

That probably won't clear up until after a reboot.

Rgds...Geoff

[Jerry_109]

Here's where it worked just now on another system:


root@hohp201[/root]
# bdf /tmp
Filesystem kbytes used avail %used Mounted on
/dev/vg00/tmp 2228224 4208 2207544 0% /tmp
root@hohp201[/root]
# fuser -u /dev/vg00/tmp
/dev/vg00/tmp: 2684o(root) 2671o(root) 2702o(root) 2693o(root) 4416c(root) 4415c(root) 4413c(root) 4417c(root) 4422c(root)

root@hohp201[/root]
# fuser -ku /dev/vg00/tmp
/dev/vg00/tmp: 2684o(root) 2671o(root) 2702o(root) 2693o(root) 4416c(root) 4415c(root) 4413c(root) 4417c(root) 4422c(root)

root@hohp201[/root]
# fuser -u /dev/vg00/tmp
/dev/vg00/tmp:

root@hohp201[/root]
# umount /tmp
root@hohp201[/root]
# bdf /tmp
Filesystem kbytes used avail %used Mounted on
/dev/vg00/root 212992 146536 66056 69% /
root@hohp201[/root]
# mount /dev/vg00/tmp /tmp
root@hohp201[/root]
# bdf /tmp
Filesystem kbytes used avail %used Mounted on
/dev/vg00/tmp 2228224 4208 2207544 0% /tmp
root@hohp201[/root]

[Sandman!]

Well then try sending SIGKILL through fuser to all the processes that maybe using /tmp and if that does not fix it then a reboot is the only way to go.

# fuser -cuk /tmp

[Bill Hassell]

Unfortunately, fuser is only 50% complete in reporting processes that have a file or directory open. The most common problem is that someone has cd'ed into the /tmp directory structure and fuser can't find the user process. That's why you must download lsof as it will always find all the processes that could be blocking an unmount.

[Leonid Mishkind]

Hi. You can use the lsof utility to see open files in you system .
http://hpux.connect.org.uk/hppd/hpux/Sysadmin/lsof-4.78/

Very useful.

Leonid.