deactivate and shrink LV /tmp

Question

How can I deactivate and shrink the Logical volume mounted as /tmp safely ?

lvm> lvreduce --size 30GB /dev/vg_server4/LogVolTmp
WARNING: Reducing active and open logical volume to 30.00 GiB
THIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce LogVolTmp? [y/n]:

thanks

I think it really depends on whether you have anything strictly requires /tmp running. Also some filesystem (e.g. btrfs) supports online shrinking, so unmount may not be necessary either. Is it a system you cannot afford downtime or so? — Tom Yan, Apr 11 '16 at 17:36
@TomYan no ... downtime under 2h is no problem. I have cPanel (apache, mysql, pureftpd) running — Ebrahim Tahernejad, Apr 11 '16 at 18:32

score 1 · Accepted Answer · answered Apr 14 '16 at 14:20

As it was already mentioned, you will most likely need to umount the FS.

When unmounting the FS, you will likely want to switch to singleuser mode to safely unmount the /tmp. (Run telinit 1, /sbin/init 1 or systemctl isolate runlevel1.target depending on distro age/brand.)

When resizing adding -r (--resizefs) switch to lvreduce/lvextend/lvresize will take care of resizing the FS and LV in the right order. Caveat: it does not handle LUKS encrypted volumes yet.

deactivate and shrink LV /tmp

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