This should be enough to fix https://bugzilla.redhat.com/show_bug.cgi?id=1856514.
But the limit should be significantly higher than 10% anyway. By setting a
limit on /tmp at 10% we'll break many reasonable use cases, even though the
machine would deal fine with a much larger fraction devoted to /tmp.
(In the first version of this patch I made it 25% with the comment that
"Even 25% might be too low.". The kernel default is 50%, and we have been using
that seemingly without trouble since https://fedoraproject.org/wiki/Features/tmp-on-tmpfs.
So let's just make it 50% again.)
See 7d85383edb.
(Another consideration is that we learned from from the whole initiative with
zram in Fedora that a reasonable size for zram is 0.5-1.5 of RAM, and that pretty
much all systems benefit from having zram or zswap enabled. Thus it is reasonable
to assume that it'll become widely used. Taking the usual compression effectiveness
of 0.2 into account, machines have effective memory available of between
1.0 - 0.2*0.5 + 0.5 = 1.4 (for zram sized to 0.5 of RAM) and
1.0 - 0.2*1.5 + 1.5 = 2.2 (for zram 1.5 sized to 1.5 of RAM) times RAM size.
This means that the 10% was really like 7-4% of effective memory.)
A comment is added to mount-util.h to clarify that tmp.mount is separate.
Limit size of various tmpfs mounts to 10% of RAM, except volatile root and /var
to 25%. Another exception is made for /dev (also /devs for PrivateDevices) and
/sys/fs/cgroup since no (or very few) regular files are expected to be used.
In addition, since directories, symbolic links, device specials and xattrs are
not counted towards the size= limit, number of inodes is also limited
correspondingly: 4MB size translates to 1k of inodes (assuming 4k each), 10% of
RAM (using 16GB of RAM as baseline) translates to 400k and 25% to 1M inodes.
Because nr_inodes option can't use ratios like size option, there's an
unfortunate side effect that with small memory systems the limit may be on the
too large side. Also, on an extremely small device with only 256MB of RAM, 10%
of RAM for /run may not be enough for re-exec of PID1 because 16MB of free
space is required.
There should be a way to turn this logic of, and DefaultDependencies=
appears to be the right option for that, hence let's downgrade this
dependency type from "implicit" to "default, and thus honour
DefaultDependencies=.
This also drops mount_get_fstype() as we only have a single user needing
this now.
A follow-up for #7076.
In the past we introduced this property just for tmp.mount. However on
todays systems usually there are many more tmpfs mounts. Most notably
mounts backing XDG_RUNTIME_DIR for each user.
Let's generalize what we already have for tmp.mount and implement the
ordering After=swap.target for all tmpfs based mounts.
If SMACK is enabled, 'smackfsroot=*' option should be specified when
/tmp is mounted since many non-root processes use /tmp for temporary
usage. If not, /tmp is labeled as '_' and smack denial occurs when
writing.
In order to do that, 'SmackFileSystemRoot=*' is newly added into
tmp.mount.
This reverts commit 409c2a13fd.
It breaks the bootup of systems which enable smack at compile time, but have no
smack enabled in the kernel. This needs a different solution.
If SMACK is enabled, 'smackfsroot=*' option should be specified in
tmp.mount file since many non-root processes use /tmp for temporary
usage. If not, /tmp is labeled as '_' and smack denial occurs when
writing.
We finally got the OK from all contributors with non-trivial commits to
relicense systemd from GPL2+ to LGPL2.1+.
Some udev bits continue to be GPL2+ for now, but we are looking into
relicensing them too, to allow free copy/paste of all code within
systemd.
The bits that used to be MIT continue to be MIT.
The big benefit of the relicensing is that closed source code may now
link against libsystemd-login.so and friends.
The default setups should be a stateless as possible. /tmp as tmpfs is
the intended default for general purpose systems.
Small temporary files should not be stored on disk; lager files, or
files which should potentially survive a reboot, belong into /var/tmp.
Also catch up with some good old UNIX history.
More details are here:
https://fedoraproject.org/wiki/Features/tmp-on-tmpfs
Yu Watanabe