[OE-core] [OE-Core][PATCH v6 0/6] systemd stateless configuration

[Alex Kiernan]

On Thu, May 2, 2019 at 10:10 PM Alex Kiernan <alex.kiernan at gmail.com> wrote:
>
>
> This patch set is largely Jonas Bonn's to move towards a "stateless"
> configuration:
>
>   These patches make some modifications to systemd with the long-term goal
>   of being able to run OE in systemd's "stateless" configuration.
>   "Stateless" boils down to building an image with empty /etc and /var
>   directories so that volatile (tmpfs) filesystems can be mounted there;
>   this requires that the system subsequently be able to populate these
>   directories dynamically, which systemd mostly takes care of if things are
>   done right.
>
>   In these patches:
>   i)   Don't include machine-id in writable images so that systemd can run
>        its first-boot machinery
>   ii)  Move systemd configuration files out of /etc
>   iii) Allow systemd to dynamically enable services and populate
>        /etc/systemd/system via the presets mechanism
>
>   There's a long way to go to get to a working "stateless" configuration.
>   Getting to a "volatile" system (just empty /var) should be easier and I'll
>   post patches moving things in that direction shortly.
>
> However as a result of the systemd 242 upgrade, which includes 01d2041e41f4
> ("meson: stop creating enablement symlinks in /etc during installation"),
> services such as systemd-networkd are no longer enabled in images.
>
> This patch set fixes this problem in addition to satisfying the goal of
> moving towards "stateless" configurations.
>
> The issue with respect to image testing during CI was caused by
> systemd-time-wait-sync.service being enabled due to the lack of a default
> preset policy:
>
> https://www.freedesktop.org/wiki/Software/systemd/Preset/#howto
>
> Changes in v6:
> - switch configuration to simple overrides in /usr/lib/systemd/*.conf.d
> - make systemd RRECOMMENDS rather than RDEPENDS on systemd-conf
> - don't exit in postinst as when that executes we're actually a
>   concatenation of all fragments
> - validate SYSTEMD_AUTO_ENABLE is `enable` or `disable`
> - rewrite systemctl-native in Python
> - moved systemctl preset-all to IMAGE_PREPROCESS so it runs after ROOTFS,
>   run for all images, not just read-only
>
> Changes in v5:
> - rebased for systemd 242
> - install default preset distribution policy of "enable nothing"
>
> Alex Kiernan (3):
>   systemd-conf: simplify creation of machine-specific configuration
>   systemctl-native: Rewrite in Python supporting preset-all and mask
>   image: call systemctl preset-all for images
>
> Jonas Bonn (3):
>   systemd: don't build firstboot by default
>   systemd: do not create machine-id
>   systemd: create preset files instead of installing in image
>
>  meta/classes/image.bbclass                    |   9 +-
>  meta/classes/rootfs-postcommands.bbclass      |   6 +
>  meta/classes/systemd.bbclass                  |  41 +-
>  .../systemd/systemd-conf/journald.conf        |   3 +
>  .../systemd/systemd-conf/logind.conf          |   2 +
>  .../systemd/systemd-conf/system.conf          |   2 +
>  .../systemd/systemd-conf/system.conf-qemuall  |   3 +
>  meta/recipes-core/systemd/systemd-conf_242.bb |  61 +--
>  .../systemd/systemd-systemctl/systemctl       | 476 ++++++++++--------
>  .../systemd/systemd/99-default.preset         |   1 +
>  meta/recipes-core/systemd/systemd_242.bb      |  26 +-
>  11 files changed, 360 insertions(+), 270 deletions(-)
>  create mode 100644 meta/recipes-core/systemd/systemd-conf/journald.conf
>  create mode 100644 meta/recipes-core/systemd/systemd-conf/logind.conf
>  create mode 100644 meta/recipes-core/systemd/systemd-conf/system.conf
>  create mode 100644 meta/recipes-core/systemd/systemd-conf/system.conf-qemuall
>  create mode 100644 meta/recipes-core/systemd/systemd/99-default.preset
>

Sigh...

this still has issues - if you boot with `ro` on the kernel command
line and without an initramfs, then / is read-only when systemd starts
and it basically refuses to do anything:

[    7.222134] systemd[1]: No hostname configured.
[    7.227266] systemd[1]: Set hostname to <localhost>.
[    7.232622] systemd[1]: System cannot boot: Missing /etc/machine-id
and /etc is mounted read-only.
[    7.241750] systemd[1]: Booting up is supported only when:
[    7.247362] systemd[1]: 1) /etc/machine-id exists and is populated.
[    7.253752] systemd[1]: 2) /etc/machine-id exists and is empty.
[    7.259757] systemd[1]: 3) /etc/machine-id is missing and /etc is writable.

Note this has nothing to do with read-only-rootfs, this is just a
regular boot... that said a bunch of things that were broken now work,
so it's progress!

I'm leaning towards having systemctl-native touch /etc/machine-id when
it runs, unless you explicitly ask for stateless in DISTRO_FEATURES...
patches to follow.

--
Alex Kiernan