[systemd-devel] [PATCH] Generate a fake systemd-fsck-root.service in the initramfs

[Harald Hoyer]

Works for me... booted with "ro" on the kernel cmdline:

$ systemctl status systemd-fsck-root.service
● systemd-fsck-root.service - File System Check on Root Device
   Loaded: loaded (/usr/lib/systemd/system/systemd-fsck-root.service; static;
vendor preset: disabled)
   Active: inactive (dead) since Mi 2015-05-06 15:37:58 CEST; 1min 44s ago
     Docs: man:systemd-fsck-root.service(8)
 Main PID: 144 (code=exited, status=0/SUCCESS)
   CGroup: /system.slice/systemd-fsck-root.service



[    1.440568]  systemd[1]: Starting Root File System Check Placeholder...
[    1.445484]  systemd[1]: Started Root File System Check Placeholder.
[…]
[    1.786864]  systemd[1]: Starting File System Check on /dev/gpt-auto-root...
[    1.804183]  systemd[1]: Started File System Check on /dev/gpt-auto-root.
[    2.015962]  systemd[1]: Mounting /sysroot...
[…]
[    2.294428]  systemd[1]: Switching root.
[…]
[    2.570286]  systemd[1]: Stopped Switch Root.
[…]
[    2.571714]  systemd[1]: Stopped File System Check on Root Device.
[    2.571859]  systemd[1]: Stopping File System Check on Root Device...
[…]
[    2.624669]  systemd[1]: Started Remount Root and Kernel File Systems.


Although "Stopping File System Check on Root Device" is strange...

On 06.05.2015 07:26, Zbigniew Jędrzejewski-Szmek wrote:
> In the initramfs, we run systemd-fsck@<sysroot-device>.service.
> In the real system we run systemd-fsck-root.service. Generate
> a fake systemd-fsck-root.service if we are running a unit check
> for the root file system. We don't really care if the real fsck unit
> fails, because the failure will be handled in some other way.
> 
> This fake unit is created and pulled in only when we actually plan to
> check the file system for /sysroot. This way we avoid having an
> active/exited systemd-fsck-root.service in the main filesystem if
> we didn't do anything.
> 
> https://bugzilla.redhat.com/show_bug.cgi?id=1201979
> 
> C.f. 956eaf2b8d6c9999024705ddadc7393bc707de02.
> ---
> Something like this?
> 
>  TODO                   |  5 -----
>  src/shared/generator.c | 30 ++++++++++++++++++++++++++++++
>  2 files changed, 30 insertions(+), 5 deletions(-)
> 
> diff --git a/TODO b/TODO
> index 430a354e84..cc827701f0 100644
> --- a/TODO
> +++ b/TODO
> @@ -113,9 +113,6 @@ Features:
>  * Maybe add support for the equivalent of "ethtool advertise" to .link files?
>    http://lists.freedesktop.org/archives/systemd-devel/2015-April/030112.html
>  
> -* fstab-generator should generate systemd-fsck-root.service when
> -  running in the initrd, and operate on the right device.
> -
>  * .timer units should optionally support CLOCK_BOOTTIME in addition to CLOCK_MONOTONIC
>  
>  * create a btrfs qgroup for /var/lib/machines, and add all container
> @@ -153,8 +150,6 @@ Features:
>  * Introduce $LISTEN_NAMES to complement $LISTEN_FDS, containing a
>    colon separated list of identifiers for the fds passed.
>  
> -* when the fstab-generator runs in the initrd, it should create a /dev/null mask for systemd-fsck-root.service, to avoid that the the root fs is fsck'ed twice.
> -
>  * maybe introduce WantsMountsFor=? Usecase:
>    http://lists.freedesktop.org/archives/systemd-devel/2015-January/027729.html
>  
> diff --git a/src/shared/generator.c b/src/shared/generator.c
> index 2dc34bf738..813ce1af9a 100644
> --- a/src/shared/generator.c
> +++ b/src/shared/generator.c
> @@ -28,8 +28,32 @@
>  #include "generator.h"
>  #include "path-util.h"
>  #include "fstab-util.h"
> +#include "fileio.h"
>  #include "dropin.h"
>  
> +static int write_fsck_root_service(const char *dir) {
> +        const char *unit;
> +        int r;
> +
> +        unit = strjoina(dir, "/systemd-fsck-root.service");
> +        log_debug("Creating %s.", unit);
> +
> +        r = write_string_file_atomic(unit,
> +                "# Automatically generated by a systemd-fstab-generator or similar\n\n"
> +                "[Unit]\n"
> +                "Description=Root File System Check Placeholder\n"
> +                "DefaultDependencies=no\n"
> +                "Before=shutdown.target\n"
> +                "\n"
> +                "[Service]\n"
> +                "ExecStart=/bin/true\n"
> +                "Type=oneshot\n"
> +                "RemainAfterExit=yes\n");
> +        if (r < 0)
> +                log_warning_errno(errno, "Failed to write unit file %s: %m", unit);
> +        return r;
> +}
> +
>  int generator_write_fsck_deps(
>                  FILE *f,
>                  const char *dir,
> @@ -79,6 +103,12 @@ int generator_write_fsck_deps(
>                          "RequiresOverridable=%1$s\n"
>                          "After=%1$s\n",
>                          fsck);
> +
> +                if (in_initrd() && path_equal(where, "/sysroot")) {
> +                        (void) write_fsck_root_service(dir);
> +                        fprintf(f,
> +                                "Wants=systemd-fsck-root.service\n");
> +                }
>          }
>  
>          return 0;
>