In mkosi, I want to add a sysupdate verb to wrap systemd-sysupdate.
The definitions will be picked up from mkosi.sysupdate/ and passed
to systemd-sysupdate. I want users to be able to write transfer
definitions that are independent of the output directory used by
mkosi. To make this possible, it should be possible to specify the
directory that transfer sources should be looked up in on the sysupdate
command line. Let's allow this via a new --transfer-source= option.
Additionally, transfer sources that want to take advantage of this
feature should specify PathRelativeTo=directory to indicate the configured
Path= is interpreted relative to the tranfer source directory specified
on the CLI.
This allows for the following transfer definition to be put in
mkosi.sysupdate:
"""
[Transfer]
ProtectVersion=%A
[Source]
Type=regular-file
Path=/
PathRelativeTo=directory
MatchPattern=ParticleOS_@v.usr-%a.@u.raw
[Target]
Type=partition
Path=auto
MatchPattern=ParticleOS_@v
MatchPartitionType=usr
PartitionFlags=0
ReadOnly=1
"""
Linux kernel v4.18 (2018-08-12) added user-namespace support to FUSE, and
bumped the FUSE version to 7.27 (see: da315f6e0398 (Merge tag
'fuse-update-4.18' of
git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse, Linus Torvalds,
2018-06-07). This means that on such kernels it is safe to enable FUSE in
nspawn containers.
In outer_child(), before calling copy_devnodes(), check the FUSE version to
decide whether enable (>=7.27) or disable (<7.27) FUSE in the container. We
look at the FUSE version instead of the kernel version in order to enable FUSE
support on older-versioned kernels that may have the mentioned patchset
backported ([as requested by @poettering][1]). However, I am not sure that
this is safe; user-namespace support is not a documented part of the FUSE
protocol, which is what FUSE_KERNEL_VERSION/FUSE_KERNEL_MINOR_VERSION are meant
to capture. While the same patchset
- added FUSE_ABORT_ERROR (which is all that the 7.27 version bump
is documented as including),
- bumped FUSE_KERNEL_MINOR_VERSION from 26 to 27, and
- added user-namespace support
these 3 things are not inseparable; it is conceivable to me that a backport
could include the first 2 of those things and exclude the 3rd; perhaps it would
be safer to check the kernel version.
Do note that our get_fuse_version() function uses the fsopen() family of
syscalls, which were not added until Linux kernel v5.2 (2019-07-07); so if
nothing has been backported, then the minimum kernel version for FUSE-in-nspawn
is actually v5.2, not v4.18.
Pass whether or not to enable FUSE to copy_devnodes(); have copy_devnodes()
copy in /dev/fuse if enabled.
Pass whether or not to enable FUSE back over fd_outer_socket to run_container()
so that it can pass that to append_machine_properties() (via either
register_machine() or allocate_scope()); have append_machine_properties()
append "DeviceAllow=/dev/fuse rw" if enabled.
For testing, simply check that /dev/fuse can be opened for reading and writing,
but that actually reading from it fails with EPERM. The test assumes that if
FUSE is supported (/dev/fuse exists), then the testsuite is running on a kernel
with FUSE >= 7.27; I am unsure how to go about writing a test that validates
that the version check disables FUSE on old kernels.
[1]: https://github.com/systemd/systemd/issues/17607#issuecomment-745418835Closes#17607
Follow-up for 99aad9a2b9
The commit changed lookup_paths_init_or_warn() call to
be fatal to manager_reload(), but invoke_main_loop()
assumes that manager_reload() would only return
recoverable error, and put the manager back to
MANAGER_OK in that case, which is spurious.
Looking at it more, it appears to be utterly unnecessary
to reinitialize LookupPaths here, given that nothing during
the reload process would change the search dirs. Let's drop
the path altogether hence.
Right now it mostly duplicates a test that already exists in
TEST-50-DISSECT.mountfsd.sh, but it serves as a template for more unprivileged
nspawn tests.
Yu Watanabe
Lennart Poettering
Mike Yuan
Daan De Meyer
Yanqing Jing
samuelvw01
Erik Sjölund
marginaldev
Luke T. Shumaker
Michal Sekletar