This is a pretty large patch, and adds support for OCI runtime bundles
to nspawn. A new switch --oci-bundle= is added that takes a path to an
OCI bundle. The JSON file included therein is read similar to a .nspawn
settings files, however with a different feature set.
Implementation-wise this mostly extends the pre-existing Settings object
to carry additional properties for OCI. However, OCI supports some
concepts .nspawn files did not support yet, which this patch also adds:
1. Support for "masking" files and directories. This functionatly is now
also available via the new --inaccesible= cmdline command, and
Inaccessible= in .nspawn files.
2. Support for mounting arbitrary file systems. (not exposed through
nspawn cmdline nor .nspawn files, because probably not a good idea)
3. Ability to configure the console settings for a container. This
functionality is now also available on the nspawn cmdline in the new
--console= switch (not added to .nspawn for now, as it is something
specific to the invocation really, not a property of the container)
4. Console width/height configuration. Not exposed through
.nspawn/cmdline, but this may be controlled through $COLUMNS and
$LINES like in most other UNIX tools.
5. UID/GID configuration by raw numbers. (not exposed in .nspawn and on
the cmdline, since containers likely have different user tables, and
the existing --user= switch appears to be the better option)
6. OCI hook commands (no exposed in .nspawn/cmdline, as very specific to
OCI)
7. Creation of additional devices nodes in /dev. Most likely not a good
idea, hence not exposed in .nspawn/cmdline. There's already --bind=
to achieve the same, which is the better alternative.
8. Explicit syscall filters. This is not a good idea, due to the skewed
arch support, hence not exposed through .nspawn/cmdline.
9. Configuration of some sysctls on a whitelist. Questionnable, not
supported in .nspawn/cmdline for now.
10. Configuration of all 5 types of capabilities. Not a useful concept,
since the kernel will reduce the caps on execve() anyway. Not
exposed through .nspawn/cmdline as this is not very useful hence.
Note that this only implements the OCI runtime logic itself. It does not
provide a runc-compatible command line tool. This is left for a later
PR. Only with that in place tools such as "buildah" can use the OCI
support in nspawn as drop-in replacement.
Currently still missing is OCI hook support, but it's already parsed and
everything, and should be easy to add. Other than that it's OCI is
implemented pretty comprehensively.
There's a list of incompatibilities in the nspawn-oci.c file. In a later
PR I'd like to convert this into proper markdown and add it to the
documentation directory.
Let's separate out the raw uid_t/gid_t handling from the username
handling. This is useful later on.
Also, let's use the right gid_t type for group types wherever
appropriate.
if we sync the legacy and unified trees before moving to the right
subcgroup then ultimately the cgroup paths in the hierarchies will be
out-of-sync... Hence, let's move the payload first, and sync then.
Addresses: https://github.com/systemd/systemd/pull/9762#issuecomment-441187979
Previously, when we'd copy an individual file we'd synthesize a
user.crtime_usec xattr with the source's creation time if we can
determine it. As the creation/birth time was until recently not
queriable form userspace this effectively just propagated the same xattr
on the source to the same xattr on the destination. However, current
kernels now allow to query the birthtime using statx() and we do make
use of that now. Which means that suddenly we started synthesizing these
xattrs much more regularly.
Doing this actually does make sense, but only in very few cases:
not for the typical regular files we copy, but certainly when dealing
with disk images. Hence, let's keep this kind of propagation, but let's
make it a flag and default to off. Then turn it on whenever we deal with
disk images, and leave it off otherwise.
This is particularly relevant as overlayfs combining a real fs, and a
tmpfs on top will result in EOPNOTSUPP when it is attempted to open a
file with xattrs for writing, as tmpfs does not support xattrs, and
hence the copy-up cannot work. Hence, let's avoid synthesizing this
needlessly, to increase compat with overlayfs.
Previously, we'd refuse the combination, and claimed we'd imply it, but
actually didn't. Let's allow the combination and imply read-only from
--volatile=, because that's what's documented, what we claim we do, and
what makes sense.
fdopen doesn't accept "e", it's ignored. Let's not mislead people into
believing that it actually sets O_CLOEXEC.
From `man 3 fdopen`:
> e (since glibc 2.7):
> Open the file with the O_CLOEXEC flag. See open(2) for more information. This flag is ignored for fdopen()
As mentioned by @jlebon in #11131.
cg_ns_supported() caches, so the condition was really checked just once, but
it looks weird to assign the return value to arg_use_cgns (if the variable is not present),
because then the other checks are effectively equivalent to
if (cg_ns_supported() && cg_ns_supported()) { ...
and later
if (!cg_ns_supported() || !cg_ns_supported()) { ...
That's what the function is for after all, and only if it's done there
we can verify the effect of .nspawn files correctly too: after all we
should not just validate that everything configured on the command line
makes sense, but the stuff configured in the .nspawn files, too.
This then let's us to ensure it's called after we parsed the cmdline,
and after we loaded the settings file, so that it these env var settings
override everything loaded from there.
This splits out a bunch of functions from fileio.c that have to do with
temporary files. Simply to make the header files a bit shorter, and to
group things more nicely.
No code changes, just some rearranging of source files.
Whenever we invoke external, foreign code from code that has
RLIMIT_NOFILE's soft limit bumped to high values, revert it to 1024
first. This is a safety precaution for compatibility with programs using
select() which cannot operate with fds > 1024.
This commit adds the call to rlimit_nofile_safe() to all invocations of
exec{v,ve,l}() and friends that either are in code that we know runs
with RLIMIT_NOFILE bumped up (which is PID 1 and all journal code for
starters) or that is part of shared code that might end up there.
The calls are placed as early as we can in processes invoking a flavour
of execve(), but after the last time we do fd manipulations, so that we
can still take benefit of the high fd limits for that.
This changes cg_enable_everywhere() to return which controllers are
enabled for the specified cgroup. This information is then used to
correctly track the enablement mask currently in effect for a unit.
Moreover, when we try to turn off a controller, and this works, then
this is indicates that the parent unit might succesfully turn it off
now, too as our unit might have kept it busy.
So far, when realizing cgroups, i.e. when syncing up the kernel
representation of relevant cgroups with our own idea we would strictly
work from the root to the leaves. This is generally a good approach, as
when controllers are enabled this has to happen in root-to-leaves order.
However, when controllers are disabled this has to happen in the
opposite order: in leaves-to-root order (this is because controllers can
only be enabled in a child if it is already enabled in the parent, and
if it shall be disabled in the parent then it has to be disabled in the
child first, otherwise it is considered busy when it is attempted to
remove it in the parent).
To make things complicated when invalidating a unit's cgroup membershup
systemd can actually turn off some controllers previously turned on at
the very same time as it turns on other controllers previously turned
off. In such a case we have to work up leaves-to-root *and*
root-to-leaves right after each other. With this patch this is
implemented: we still generally operate root-to-leaves, but as soon as
we noticed we successfully turned off a controller previously turned on
for a cgroup we'll re-enqueue the cgroup realization for all parents of
a unit, thus implementing leaves-to-root where necessary.
Ideally, coccinelle would strip unnecessary braces too. But I do not see any
option in coccinelle for this, so instead, I edited the patch text using
search&replace to remove the braces. Unfortunately this is not fully automatic,
in particular it didn't deal well with if-else-if-else blocks and ifdefs, so
there is an increased likelikehood be some bugs in such spots.
I also removed part of the patch that coccinelle generated for udev, where we
returns -1 for failure. This should be fixed independently.
Pretty much everything uses just the first argument, and this doesn't make this
common pattern more complicated, but makes it simpler to pass multiple options.
From #10526:
$ sudo systemd-nspawn -i image
Spawning container image on /home/zbyszek/src/mkosi/image.
Press ^] three times within 1s to kill container.
Short read while reading cgroup mode.
Lennart Poettering
Zbigniew Jędrzejewski-Szmek
Chris Down
Yu Watanabe