[systemd-devel] [PATCH 3/3] Use a stamp file to avoid running systemd-fsck-root.service twice

[Andrei Borzenkov]

В Sat,  2 May 2015 13:16:59 -0400
Zbigniew Jędrzejewski-Szmek <zbyszek at in.waw.pl> пишет:

> In the initramfs, we run systemd-fsck@<sysroot-device>.service.
> In the real system we run systemd-fsck-root.service. It is hard
> to pass the information that the latter should not run if the first
> succeeded using unit state only.
> 
> - in the real system, we need a synchronization point between the fsck
>   for root and other fscks, to express the dependency to run this
>   systemd-fsck at .service "before all other systemd-fsck@ units". We
>   cannot express it directly, because there are no wildcard
>   dependencies. We could use a target as a sychronization point, but
>   then we would have to provide drop-ins to order
>   systemd-fsck at -.service before the target, and all others after it,
>   which becomes messy. The currently used alternative of having a
>   special unit (systemd-fsck-root.service) makes it easy to express
>   this dependency, and seems to be the best solution.
> 
> - we cannot use systemd-fsck-root.service in the initramfs, because
>   other fsck units should not be ordered after it. In the real system,
>   the root device is always checked and mounted before other filesystems,
>   but in the initramfs this doesn't have to be true: /sysroot might be
>   stacked on other filesystems and devices.
> 
> - the name of the root device can legitimately be specified in a
>   different way in the initramfs (on the kernel command line, or
>   automatically discovered through GPT), and in the real fs (in /etc/fstab).
>   Even if we didn't need systemd-fsck-root.service as a synchronization
>   point, it would be hard to ensure the same instance parameter is
>   provided for systemd-fsck at .service in the initrams and the real
>   system.
> 
> Let's use a "side channel" to pass this information.
> /run/systemd/fsck-root-done is touched after fsck in the initramfs
> succeeds, through an ExecStartPost line in a drop-in for
> systemd-fsck at sysroot.service.

You probably should mention that it effectively reverts
956eaf2b8d6c9999024705ddadc7393bc707de02.

> 
> https://bugzilla.redhat.com/show_bug.cgi?id=1201979
> ---
>  src/shared/generator.c             | 7 +++++++
>  units/systemd-fsck-root.service.in | 1 +
>  2 files changed, 8 insertions(+)
> 
> diff --git a/src/shared/generator.c b/src/shared/generator.c
> index 7b2f846175..a71222d1cb 100644
> --- a/src/shared/generator.c
> +++ b/src/shared/generator.c
> @@ -78,6 +78,13 @@ int generator_write_fsck_deps(
>                          "RequiresOverridable=%1$s\n"
>                          "After=%1$s\n",
>                          fsck);
> +
> +                if (in_initrd() && path_equal(where, "/sysroot"))
> +                        return write_drop_in_format(dir, fsck, 50, "stamp",
> +                                                    "# Automatically generated by %s\n\n"
> +                                                    "[Service]\n"
> +                                                    "ExecStartPost=-/bin/touch /run/systemd/fsck-root-done\n",
> +                                                    program_invocation_short_name);
>          }
>  
>          return 0;
> diff --git a/units/systemd-fsck-root.service.in b/units/systemd-fsck-root.service.in
> index 3617abf04a..48dacc841c 100644
> --- a/units/systemd-fsck-root.service.in
> +++ b/units/systemd-fsck-root.service.in
> @@ -11,6 +11,7 @@ Documentation=man:systemd-fsck-root.service(8)
>  DefaultDependencies=no
>  Before=local-fs.target shutdown.target
>  ConditionPathIsReadWrite=!/
> +ConditionPathExists=!/run/systemd/fsck-root-done
>  
>  [Service]
>  Type=oneshot