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When chase_symlinks() is called on something on a doesn't exist, it immediately
returns an error. But we were relying on it to prepend "/sysroot/". If it
fails, we need to do that ourselves.
For example, with /sysroot/etc/fstab containing a line for /foo, if /sysroot/foo
doesn't exist, we'd generate a mount point for /foo.
Originally (6b1dc2bd3cdb3bd932b0692be636ddd2879edb92) we had 'pre' and 'post'
to refer to remote-fs-pre.target and remote-fs.target or local-fs-pre.target
and local-fs.target. But 'pre' is long gone, and 'post' by itself doesn't
make much sense. Rename it for clarity.
Mount information can come from /etc/fstab, /sysroot/etc/fstab, and
/proc/cmdline. Even when we had the path to the right source handy, we would
often write something inaccurate. In particular, in the initrd, we would
generally write "/etc/fstab" instead of "/sysroot/etc/fstab" for no good
reason.
All units in units/ follow this pattern, as do all other generators that we
provide. The question of the order was raised in
https://github.com/systemd/zram-generator/pull/90#discussion_r684965984,
and I think it's nice to make it consistent everywhere
(What= before Where= matches mount(8) and fstab(5)).
The naming of variables is very inconsistent. I tried to use more
modern style naming (UNDERSCORED_TITLE_CASE), but I didn't change existing
names too much. Only SYSTEM_DATA_UNIT_PATH is renamed to SYSTEM_DATA_UNIT_DIR
to match SYSTEM_CONFIG_UNIT_DIR.
Let's rename MountpointsFlags → MountPointFlags. In most of our codebase
we name things mount_point/MountPoint rather than mountpoint/Mountpoint,
do so here too.
Also, prefix the enum values with "MOUNT_". The fact the enum values
weren#t prefixed was pretty unique in our codebase, and pretty
surprising. Let's fix that.
This is just refactoring, no actual change in behaviour
This changes the fstab-generator to handle mounting of /usr/ a bit
differently than before. Instead of immediately mounting the fs to
/sysroot/usr/ we'll first mount it to /sysusr/usr/ and then add a
separate bind mount that mounts it from /sysusr/usr/ to /sysroot/usr/.
This way we can access /usr independently of the root fs, without for
waiting to be mounted via the /sysusr/ hierarchy. This is useful for
invoking systemd-repart while a root fs doesn't exist yet and for
creating it, with partition data read from the /usr/ hierarchy.
This introduces a new generic target initrd-usr-fs.target that may be
used to generically order services against /sysusr/ to become available.
With some versions of the compiler, the _cleanup_ attr makes it think
the variable might be freed/closed when uninitialized, even though it
cannot happen. The added cost is small enough to be worth the benefit,
and optimized builds will help reduce it even further.
Apart from tests, the new argument isn't used anywhere, so there should be no
functional change. Note that the two arms of the big conditional are switched, so the
diff is artificially inflated. The actual code change is rather small. I dropped the
path which extracts ret_value manually, because it wasn't supporting unescaping of the
escape character properly.
It's useful to be able to combine a regular /usr/ file system with a
tmpfs as root, for an OS that boots up in volatile mode on every single
boot. Let's add explicit support for this via root=tmpfs.
Note the relationship to the existing systemd.volatile= option:
1. The kernel command line "root=/dev/… systemd.volatile=yes" will mount
the specified root fs, and then hide everything at the top by
overmounting it with a tmpfs, except for the /usr subtree.
2. The kernel command line "root=tmpfs mount.usr=/dev/…" otoh will mount
a toot fs at the top (just like the case above), but will then mount
the top-level dir of the fs specified in mount.usr= directly below
it.
Or to say this differently: in the first case /usr/ from the physical
storage fs is going to become /usr/ of the hierarchy ultimately booted,
while in the second case / from the physical storage fs is going to
become /usr of the hierarchy booted.
Philosophically I figure systemd.volatile= is more an option for
"one-off" boots, while root=tmpfs is something to have as default mode
of operation for suitable images.
This is currently hard to test reasonably, since Dracut refuses to
accept root=tmpfs. This needs to be addressed separately though.
If an entry in fstab uses "x-systemd.automount" option and also asks for
additionnal dependencies via x-systemd.requires or such, then the dependencies
were applied to the automount unit.
But this unlikely to do the right thing and is inconsistent with what's done
for network mounts.
Indeed when an fstab entries has "_netdev,x-systemd.automount" options, the
dependencies against the network requested by "_netdev" are (correctly) applied
to the mount unit only and the automount unit remains ordered against
local-fs.target.
The same logic should be followed when extra deps are specified via the mount
options as automount units should always be ordered against local-fs.target.
Note: in general explicit deps specified via mount options should be used with
care and should be used to specify dependencies on other mount units only as it
can easily create ordering cycles otherwise like it's been seen in
https://github.com/systemd/systemd-stable/issues/69. Mount units (as well as
automount ones) are ordered before local-fs.target by default which is a
low-level target that most other units depend on.
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.
First After=local-fs-pre.target wasn't described in the man page although it's
part of the default dependencies automatically set by pid1.
Secondly, Before=local-fs.target was only set if the automount unit was
generated from the fstab-generator because the dep was explicitly
generated. It was also not documented as a default dependency.
Fix it by managing the dep from pid1 instead.
fstab-generator was also handling the default ordering dependencies for mount
units setup in initrd. To do that it was turning the defaults dependencies off
completely and ordered the mount unit against either local-fs.target or
initrd-fs.target or initrd-root-fs.target itself.
But it had the bad side effect to also remove all other default dependencies as
well. Thus if an initrd mount was using _netdev, the network dependencies were
missing.
In general fstab-generator shouldn't use DefaultDependecies=no because it can
handle only a small set of the default dependencies the rest are dealt by pid1.
So this patch makes pid1 handle all default dependencies.
Teaches systemd-fstab-generator these two unit options,
creating appropriate dependencies on the generated .mount
units. When used, they override any other automatically
generated dependencies, such as local-fs.target, and are
NOT suppressed by noauto. The new options are ignored for
/, in the same way that noauto is ignored.
Fixes: #14380
Signed-off-by: Antonio Russo <antonio.e.russo@gmail.com>
