The code to evaluate the kernel command line option was busted because it
was doing 'return b == !!r' at a point where 'r > 0'. Thus we'd return "true"
in both cases:
$ SYSTEMD_PROC_CMDLINE=systemd.condition-first-boot build/systemd-analyze condition 'ConditionFirstBoot=true'
test.service: ConditionFirstBoot=true succeeded.
Conditions succeeded.
$ SYSTEMD_PROC_CMDLINE=systemd.condition-first-boot build/systemd-analyze condition 'ConditionFirstBoot=false'
test.service: ConditionFirstBoot=false succeeded.
Conditions succeeded.
We only use 'ConditionFirstBoot=true' in units, so this wasn't noticed.
But I think the logic is broken in general: the condition should evaluate as
true only during initial boot. If we rerun the units at later points, we should
not consider ConditionFirstBoot to be true.
Also, the first boot logic is also used in pid1 itself. AFAICT, for two
things: in first boot machine-id is initialized transiently (this allows
first-boot operations to be restarted if boot fails), and preset-all is
executed. But this logic was different and separate from the logic to
evaluate ConditionFirstBoot. The distinction is abolished, and the operations
in pid1 now use the same logic as ConditionFirstBoot, which means that the
kernel command line option is checked, and condition_test_first_boot()
just tests whether pid1 thinks we're in first boot.
This makes things easier to grok for the user: there's just one condition for
"first boot" and it applies to both pid1 and units.
This documents that explicit `Before=`/`After=` dependencies can be
used to selectively override implicit ordering coming from default
dependencies. That allows for more granular control compared to the
already documented `DefaultDependencies=no` option.
The alternative approach came up in a discussion around the ordering
of `boot-complete.target`, so this also adds an explicit suggestion
in that direction to the "Automatic Boot Assessment" documentation.
Ref: https://lists.freedesktop.org/archives/systemd-devel/2022-September/048330.html
So this is a bit of a bikeshedding thing. But I think we should do this
nonetheless, before this is released.
Playing around with the glob matches I realized that "=$" is really hard
to grep for, since in shell code it's an often seen construct. Also,
when reading code I often found myself thinking first that the "$"
belongs to the rvalue instead of the operator, in a variable expansion
scheme.
If we move the $ character to the left hand, I think we are on the safer
side, since usually lvalues are much more restricted in character sets
than rvalues (at least most programming languages do enforce limits on
the character set for identifiers).
It makes it much easier to grep for the new operator, and easier to read
too. Example:
before:
ConditionOSRelease=ID=$fedora-*
after:
ConditionOSRelease=ID$=fedora-*
The only reason to do this is to ensure uniformity with the other
options, that work like this, i.e. ConditionOSRelease= or
ConditionSecurity=.
This is a compatibility break, but a minor one, given that string
comparison and version comparison is mostly the same for equality and
inequality.
These two operators always indicate ordering comparisons, as opposed to
"=" and "!=" which depending on context mean literal string compares.
This is useful for ConditionOSRelease= for example, as this means
there's now always a way to do version compares.
Often I end up debugging a problem on a system, and I
do e.g. `journalctl --grep=failed|error`. The use of the term
"failed" for condition checks adds a *lot* of unnecessary noise into
this.
Now, I know this regexp search isn't precise, but it has proven
to be useful to me.
I think "failed" is too strong of a term as a baseline, and also
just stands out to e.g. humans watching their servers boot or
whatever.
The term "met condition" is fairly widely used, e.g.
https://stackoverflow.com/questions/63751794/what-does-the-condition-is-met-exactly-mean-in-programming-languages
Use that instead.
/bin/sh as a shell is punishing. There is no good reason to make
the occasional root login unpleasant.
Since /bin/sh is usually /bin/bash in compat mode, i.e. if one is
available, the other will be too, /bin/bash is almost as good as a default.
But to avoid a regression in the situation where /bin/bash (or
DEFAULT_USER_SHELL) is not installed, we check with access() and fall back
to /bin/sh. This should make this change in behaviour less risky.
(FWIW, e.g. Fedora/RHEL use /bin/bash as default for root.)
This is a follow-up of sorts for 53350c7bba,
which added the default-user-shell option, but most likely with the idea
of using /bin/bash less ;)
Fixes#24369.
%R is already used in service manager specifier expansion (cgroup root),
hence use a different char, that was so far not used.
Follow-up for: 6ceb0a4094
