Practical questions for having /tmp and /var on same partition

Hi.

I just installed MX Linux onto a computer, and tough the installer does provide an option to have separate / /root /home and swap partitions, it does not natively offer the user to specify partitions to put /var and /temp.

Therefore, I have set aside 25BG free space for this purpose. I also want to put /var and /tmp on same one partition.

On this page - unix.stackexchange.com/../why-put-things-other-than-home-to-a-separate-partition it says:

var and /tmp can be filled up by user programs or daemons. Therefore it can be safe to have these in separate partitions that would prevent /, the root partition, to be 100% full, and would hit your system badly. To avoid having two distinct partitions for these, it is not uncommon to see /tmp being a symlink to /var/tmp.

The first practical question - what steps are necessary to do this? According to last post in this askubuntu forum thread:

if you provide an existing directory instead of the link name, ln will create a link inside that directory

I've made symlinks before, but this confuses me.


Thanks in advance

You will probably have to do these steps from a rescue DVD. If you try them on a live system the system will probably crash part way through the rearrangement.

Format the new partition.

Move the contents of /var to the new partition leaving /var as an empty directory on /.

change /etc/fstab to mount the new partition on /var

delete /tmp on / and recreate /tmp on / as a symbolic link to /var/tmp

The only possible problem I see with what you are attempting is if the boot process uses /tmp before /var is mounted through /etc/fstab. I don't think that is what actually happens so I think it should work.

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Steve Stites

Thanks a lot #jailbait, that make sense. See if I got time to test this tomorrow.

If it get problems with this, it's a newly OS installed so not much time wasted anyway.

The practice of putting /var and /tmp on separate partitions dates back through the mists of time when hard drives were still relatively new and extremely small. With today's hard drives, it should not be necessary.

I common allocate 25-30GB for my root partition, which contains everything except /home, and have never experienced any issues related the /var and /tmp. (Before I started doing that, I would have just one root partition containing everything, and also never encountered any issues.)

The only possible problem I see with what you are attempting is if the boot process uses /tmp before /var is mounted through /etc/fstab. I don't think that is what actually happens so I think it should work.

Good point!
systemd places files in /tmp
If these are overmounted, it might misbehave.

EDIT
I think it uses the /tmp later, not before mounting, so it is likely not a real problem.

Originally Posted by MadeInGermany I think it uses the /tmp later, not before mounting, so it is likely not a real problem.

The new idea is to use /run.

Putting /tmp and /var on their own partition(s) is only useful for servers. There a lot of users may create a lot of data on /tmp, while databases typically make use of /var to keep track of things.

FWIW, /tmp is a tmpfs (aka RAM disk) on my system.
Major distros seem to disagree about what exactly /tmp should be, but I think that's the right way.
There's more:

$> grep -w tmpfs /etc/mtab
run /run tmpfs rw,nosuid,nodev,relatime,mode=755 0 0
tmpfs /dev/shm tmpfs rw,nosuid,nodev 0 0
tmpfs /sys/fs/cgroup tmpfs ro,nosuid,nodev,noexec,size=4096k,nr_inodes=1024,mode=755 0 0
tmpfs /tmp tmpfs rw,nosuid,nodev,size=3538532k,nr_inodes=409600 0 0
tmpfs /run/user/1000 tmpfs rw,nosuid,nodev,relatime,size=707704k,nr_inodes=176926,mode=700,uid=1000,gid=1000 0 0

Originally Posted by ondoho FWIW, /tmp is a tmpfs (aka RAM disk) on my system.

tmpfs, AKA “a symlink to /dev/shm” or just any kind of ramdisk for temporary data should be a natural choice. I do not know if my use of the temp-directory qualifies me as a security-freak. But knowing that wiping RAM is quite different from wiping a hard-disk has its charms. – Knowing that not doing anything at all is enough for a RAM-disk, too.