From 93651582aef1ee626dc6f8d032195acd73bc9372 Mon Sep 17 00:00:00 2001

From: Jonathan Lebon <jonathan@jlebon.com>

Date: Mon, 23 Mar 2020 12:25:19 -0400

Subject: [PATCH] manager: optionally, do a full preset on first boot

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A compile time option is added to select behaviour: by default

UNIT_FILE_PRESET_ENABLE_ONLY is still used, but the intent is to change to

UNIT_FILE_PRESET_FULL at some point in the future. Distros that want to

opt-in can use the config option to change the behaviour.

(The option is just a boolean: it would be possible to make it multi-valued,

and allow full, enable-only, disable-only, none. But so far nobody has asked

for this, and it's better not to complicate things needlessly.)

With the configuration option flipped, instead of only doing enablements,

perform a full preset on first boot. The reason is that although

`/etc/machine-id` might be missing, there may be other files provisioned in

`/etc` (in fact, this use case is mentioned in `log_execution_mode`). Some of

those possible files include enablement symlinks even if presets dictate it

should be disabled.

Such a seemingly contradictory situation occurs in {RHEL,Fedora} CoreOS,

where we ship `/etc` as if `preset-all` were called. However, we want to

allow users to disable default-enabled services via Ignition, which does

this by creating preset dropins before switchroot. (For why we do

`preset-all` at compose time, see:

https://github.com/coreos/fedora-coreos-config/pull/77).

For example, the composed FCOS image has a `enable zincati.service`

preset and an enablement for that in `/etc`, while at boot time when we

switch root, there may be a `disable zincati.service` preset with higher

precedence. In that case, we want systemd to disable the service.

This is essentially a revert of 304b3079a203. It seems like systemd

*used* to do this, but it was changed to try to make the container

workflow a bit faster.

Resolves: https://github.com/coreos/fedora-coreos-tracker/issues/392

Co-authored-by: Zbigniew Jędrzejewski-Szmek <zbyszek@in.waw.pl>

---

 meson.build        | 3 +++

 meson_options.txt  | 2 ++

 src/core/manager.c | 4 +++-

 3 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/meson.build b/meson.build

index 582e33c9a73d..72e586aa97c7 100644

--- a/meson.build

+++ b/meson.build

@@ -285,6 +285,8 @@ conf.set10('MEMORY_ACCOUNTING_DEFAULT',                       memory_accounting_

 conf.set('STATUS_UNIT_FORMAT_DEFAULT',                        'STATUS_UNIT_FORMAT_' + status_unit_format_default.to_upper())

 conf.set_quoted('STATUS_UNIT_FORMAT_DEFAULT_STR',             status_unit_format_default)

+conf.set10('FIRST_BOOT_FULL_PRESET',                          get_option('first-boot-full-preset'))

+

 #####################################################################

 cc = meson.get_compiler('c')

@@ -4271,6 +4273,7 @@ foreach tuple : [

         ['link-networkd-shared',  get_option('link-networkd-shared')],

         ['link-timesyncd-shared', get_option('link-timesyncd-shared')],

         ['link-boot-shared',      get_option('link-boot-shared')],

+        ['first-boot-full-preset'],

         ['fexecve'],

         ['standalone-binaries',   get_option('standalone-binaries')],

         ['coverage',              get_option('b_coverage')],

diff --git a/meson_options.txt b/meson_options.txt

index 2a030ac28ec0..28765f900e87 100644

--- a/meson_options.txt

+++ b/meson_options.txt

@@ -27,6 +27,8 @@ option('link-timesyncd-shared', type: 'boolean',

        description : 'link systemd-timesyncd and its helpers to libsystemd-shared.so')

 option('link-boot-shared', type: 'boolean',

        description : 'link bootctl and systemd-bless-boot against libsystemd-shared.so')

+option('first-boot-full-preset', type: 'boolean', value: false,

+       description : 'during first boot, do full preset-all (default will be changed to true later)')

 option('static-libsystemd', type : 'combo',

        choices : ['false', 'true', 'pic', 'no-pic'],

diff --git a/src/core/manager.c b/src/core/manager.c

index 18daff66c780..f4dacef1005d 100644

--- a/src/core/manager.c

+++ b/src/core/manager.c

@@ -1728,7 +1728,9 @@ static void manager_preset_all(Manager *m) {

                 return;

         /* If this is the first boot, and we are in the host system, then preset everything */

-        r = unit_file_preset_all(LOOKUP_SCOPE_SYSTEM, 0, NULL, UNIT_FILE_PRESET_ENABLE_ONLY, NULL, 0);

+        UnitFilePresetMode mode = FIRST_BOOT_FULL_PRESET ? UNIT_FILE_PRESET_FULL : UNIT_FILE_PRESET_ENABLE_ONLY;

+

+        r = unit_file_preset_all(LOOKUP_SCOPE_SYSTEM, 0, NULL, mode, NULL, 0);

         if (r < 0)

                 log_full_errno(r == -EEXIST ? LOG_NOTICE : LOG_WARNING, r,

                                "Failed to populate /etc with preset unit settings, ignoring: %m");