In order to support offline updates to /usr, we need to be able to run
certain tasks on next boot-up to bring /etc and /var in line with the
updated /usr. Hence, let's devise a mechanism how we can detect whether
/etc or /var are not up-to-date with /usr anymore: we keep "touch
files" in /etc/.updated and /var/.updated that are mtime-compared with
/usr. This means:
Whenever the vendor OS tree in /usr is updated, and any services that
shall be executed at next boot shall be triggered, it is sufficient to
update the mtime of /usr itself. At next boot, if /etc/.updated and/or
/var/.updated is older than than /usr (or missing), we know we have to
run the update tools once. After that is completed we need to update the
mtime of these files to the one of /usr, to keep track that we made the
necessary updates, and won't repeat them on next reboot.
A subsequent commit adds a new ConditionNeedsUpdate= condition that
allows checking on boot whether /etc or /var are outdated and need
updating.
This is an early step to allow booting up with an empty /etc, with
automatic rebuilding of the necessary cache files or user databases
therein, as well as supporting later updates of /usr that then propagate
to /etc and /var again.
We install two sysctl snippets ourselves, hence the condition will
always trigger, so no point in tryng to optimize things with this, it
just will make things slower, if anything.
There's no point in conditionalizing systemd-tmpfiles at boot, since we
ship tmpfiles snippets ourselves, hence they will always trigger anyway.
Also, there's no reason to pull in local-fs.target from the service,
hence drop that.
systemd-sysusers is a tool to reconstruct /etc/passwd and /etc/group
from static definition files that take a lot of inspiration from
tmpfiles snippets. These snippets should carry information about system
users only. To make sure it is not misused for normal users these
snippets only allow configuring UID and gecos field for each user, but
do not allow configuration of the home directory or shell, which is
necessary for real login users.
The purpose of this tool is to enable state-less systems that can
populate /etc with the minimal files necessary, solely from static data
in /usr. systemd-sysuser is additive only, and will never override
existing users.
This tool will create these files directly, and not via some user
database abtsraction layer. This is appropriate as this tool is supposed
to run really early at boot, and is only useful for creating system
users, and system users cannot be stored in remote databases anyway.
The tool is also useful to be invoked from RPM scriptlets, instead of
useradd. This allows moving from imperative user descriptions in RPM to
declarative descriptions.
The UID/GID for a user/group to be created can either be chosen dynamic,
or fixed, or be read from the owner of a file in the file system, in
order to support reconstructing the correct IDs for files that shall be
owned by them.
This also adds a minimal user definition file, that should be
sufficient for most basic systems. Distributions are expected to patch
these files and augment the contents, for example with fixed UIDs for
the users where that's necessary.
There might be implementations around where the network-online logic
might not talk to any network configuration service (and thus not have
to wait for it), hence let's explicitly order network-online.target
after network.target to avoid any ambiguities.
network-pre.target is a passive target that should be pulled in by
services that want to be executed before any network is configured (for
example: firewall scrips).
network-pre.target should be ordered before all network managemet
services (but not be pulled in by them).
network-pre.target should be order after all services that want to be
executed before any network is configured (and be pulled in by them).
If two lines refer to paths that are suffix and prefix of each other,
then always process the prefix first, the suffix second. In all other
cases strictly process rules in the order they appear in the files.
This makes creating /var/run as symlink to /run a lot more fun, since it
is automatically created first.
"m" so far has been a non-globbing version of "z". Since this makes it
quite redundant, let's get rid of it. Remove "m" from the man pages,
beef up "z" docs instead, and make "m" nothing more than a compatibility
alias for "z".
Lennart Poettering
Kay Sievers
Thomas Hindoe Paaboel Andersen
Mantas Mikulėnas
Umut Tezduyar Lindskog
Ronny Chevalier