[conspire] /var/tmp - non-volatile: Re: VMs, qemu-kvm, ...

[Michael Paoli]

> Date: Fri, 21 Dec 2018 21:58:49 -0800
> From: Rick Moen <rick at linuxmafia.com>
> To: conspire at linuxmafia.com
> Subject: Re: [conspire] VMs, qemu-kvm, ...
> Message-ID: <20181222055849.GK7928 at linuxmafia.com>

> I'm not there yet.)  Need to consider what in addition to /tmp and
> /var/tmp to mount as tmpfs.

Per FHS[1], etc.[2]
/var/tmp[3] is non-volatile - notably files *are* preserved in /var/tmp
across reboot, so tmpfs isn't suitable for /var/tmp.
Whereas tmpfs is fine for /tmp[4], which is or may be volatile (it is
recommended that files in /tmp be deleted with a reboot - so volatile
filesystem such as tmpfs automagically covers that recommendation).
Essentially, if contents are moot or should be gone/emptied with/upon
reboot, tmpfs may be a good candidate.  E.g. /tmp, /var/run (which I notice
Debian has also, on current stable, made as tmpfs apparently by default:
$ (cd /var/run && pwd -P && df -h .)
/run
Filesystem      Size  Used Avail Use% Mounted on
tmpfs           100M  7.1M   93M   8% /run
$
)

1. http://www.pathname.com/fhs/
2.  
http://refspecs.linuxfoundation.org/LSB_5.0.0/LSB-Core-generic/LSB-Core-generic/execenvfhs.html
3.  
http://www.pathname.com/fhs/pub/fhs-2.3.html#VARTMPTEMPORARYFILESPRESERVEDBETWEE
4. http://www.pathname.com/fhs/pub/fhs-2.3.html#TMPTEMPORARYFILES