nss-altfiles may be needed for a stateless OS. It is a NSS extension
which allows moving /etc/passwd and friends into a read-only location
like /usr/share/defaults/etc. That path is what the Clear Linux patches
for shadow use and thus what we pick here.

Signed-off-by: Patrick Ohly <[email protected]>

Clear Linux uses nss-altfiles. It has regular releases and
should be good enough for refkit, too.

Signed-off-by: Patrick Ohly <[email protected]>

This is a cleaned up and updated version of the stateless work that
was done before.

It introduces "stateless" as distro and image feature. All of the
functionality is in stateless.bbclass, which also has
documentation. Currently the class is meant to be inherited globally,
because it enables additional patches for individual recipes
according to the STATELESS_SRC variables set by the .inc files.

This approach was chosen as an interim solution because it keeps those
changes all in individual files, instead of scattering them across
different .bbappends or upstream recipes. Also, most of the patches
come straight from the Clear Linux Project without modifications, so
it cannot be guaranteed that they always apply. Ideally, the patches
should go into the recipes that they are patching or (better)
upstream.

Most of the functionality is around the rootfs transformation. The
idea here is that packages and rootfs creation do not need to be
modified in several cases. For images that use a whole-disk update
mechanism, additional post-processing can move configuration files
around and change them as needed.

In other cases (like not installing unnecessary example config files
into /etc), the upstream recipe would need to be changed, so there is
further work left for OE and Yocto. This commit can serve as a
starting point for a discussion arounnd that.

Signed-off-by: Patrick Ohly <[email protected]>

Once we have added users and groups to the /etc databases, the systemd
sysusers.d config files shouldn't have any effect any more at runtime
and thus can be removed from images.

This works around a limitation of the current implementation and/or a
bug in the base files: because the user "nobody" exists, the current
implementation does nothing. But there is no group "nobody", and
systemd then adds that at runtime. That prevents updating /etc/group
with OSTree, because the file is always considered as "locally
modified by admin".

Signed-off-by: Patrick Ohly <[email protected]>

The main part of the test is that a new system user is active after an
update. Optionally, the test does the update while a local user has
been added.

The normal OSTree /etc handling is not enough for the full test: once
/etc/passwd and /etc/group were modified by adding the local user,
that copy of the files continue to be used and the new system user is
not registered after the update.

So for now we only enable the "light" test.

Signed-off-by: Patrick Ohly <[email protected]>

The test_update_user test only passed after ensuring that booting
didn't modify /etc/group. We should have an explicit check for that.

Signed-off-by: Patrick Ohly <[email protected]>

nsswitch.conf turned out to be a problematic choice, because some
stateless configurations move it away. host.conf is slight better.

Now we also explicitly test that the configured files are really
present. That makes mis-configured tests more obvious.

Signed-off-by: Patrick Ohly <[email protected]>

When there is a dangling symlink, the resulting error message did
not make it clear how to suppress the error for valid symlinks.
Now it mentions REFKIT_QA_IMAGE_SYMLINK_WHITELIST and what was checked
for in it.

The path resolution uses the same string before giving the full path
on the build host.

Signed-off-by: Patrick Ohly <[email protected]>

This enables the "stateless" distro feature and the "stateless" image
for all refkit-image.bbclass images.

However, only the changes that do no require upstream source code
patching get enabled. For example, systemd configuration gets moved
from /etc entirely into /usr. This is a choice we make for the
"refkit" distro. "refkit-config.inc" merely activates the base
stateless support, without any of the .inc files which actually cause
changes.

Advanced changes like allowing local user management separately from
the system users are not enabled because they depend on
patches. Enabling those changes would increase the risk that building
IoT Refkit breaks when OE-core gets updated, and at this point it is
not certain whether that is a risk worth taking.

Signed-off-by: Patrick Ohly <[email protected]>