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

[Zbigniew Jędrzejewski-Szmek]

On Wed, May 06, 2015 at 03:50:08PM +0200, Harald Hoyer wrote:
> 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...
Hm, that's strange. This would suggest that sd-fsck-root.service is not
wanted by anything in your system. I wonder if this is because you
have gpt-auto-root, and I'm using plain old fstab.

$ systemctl show -p WantedBy,RequiredBy,RequiredByOverridable systemd-fsck-root
RequiredBy=
RequiredByOverridable=
WantedBy=local-fs.target

Zbyszek

> 
> 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;
> > 
> 
>