[Buildroot] systemd and journald

[Buildroot] systemd and journald

[Yann E. MORIN]

Gabe, ?ric, Maxime, All,

I've been toying around with systemd lately, and I've stumbled on a
problem with our skeleton and the expectations of systemd.

Please bear in imind that I've just started, so I may be doing
somnething weird and/or incorrect. Anyway...

I'm using this defconfig (on rpi0, but that should not be specific to
the rpi):

    BR2_arm=y
    BR2_arm1176jzf_s=y
    BR2_PACKAGE_HOST_LINUX_HEADERS_CUSTOM_4_4=y
    BR2_TOOLCHAIN_BUILDROOT_GLIBC=y
    BR2_GLIBC_VERSION_2_23=y
    BR2_BINUTILS_VERSION_2_26_X=y
    BR2_GCC_VERSION_5_X=y
    BR2_TOOLCHAIN_BUILDROOT_CXX=y
    BR2_INIT_SYSTEMD=y
    BR2_ROOTFS_POST_IMAGE_SCRIPT="board/raspberrypi0/post-image.sh"
    BR2_LINUX_KERNEL=y
    BR2_LINUX_KERNEL_CUSTOM_GIT=y
    BR2_LINUX_KERNEL_CUSTOM_REPO_URL="https://github.com/raspberrypi/linux.git"
    BR2_LINUX_KERNEL_CUSTOM_REPO_VERSION="26f3b72a9c049be10e6af196252283e1f6ab9d1f"
    BR2_LINUX_KERNEL_USE_CUSTOM_CONFIG=y
    BR2_LINUX_KERNEL_CUSTOM_CONFIG_FILE="$(O)/linux.config"
    BR2_LINUX_KERNEL_DTS_SUPPORT=y
    BR2_LINUX_KERNEL_INTREE_DTS_NAME="bcm2708-rpi-b-plus"
    BR2_PACKAGE_RPI_FIRMWARE=y
    # BR2_PACKAGE_RPI_FIRMWARE_INSTALL_DTB_OVERLAYS is not set
    BR2_PACKAGE_SYSTEMD_JOURNAL_GATEWAY=y
    BR2_PACKAGE_SYSTEMD_BOOTCHART=y
    BR2_PACKAGE_SYSTEMD_NETWORKD=y
    BR2_TARGET_ROOTFS_EXT2=y
    BR2_TARGET_ROOTFS_EXT2_4=y
    # BR2_TARGET_ROOTFS_TAR is not set
    BR2_PACKAGE_HOST_DOSFSTOOLS=y
    BR2_PACKAGE_HOST_GENIMAGE=y
    BR2_PACKAGE_HOST_MTOOLS=y

This is using our default skeleton.

In this case, the journal is not accessible:

    # journalctl
    No journal files were found.
    -- No entries --

That's because the journal is started before /tmp is mounted:

             Starting Journal Service...
    [...]
    [  OK  ] Started Journal Service.
    [...]
             Mounting /tmp...
    [  OK  ] Mounted /tmp.

So, because our /var/log is a symlink to /tmp , the journal is correctly
created in /tmp/journal/c30ad28b21d444ba9fff7fb25b5454b1/system.journal
but since another filesystem is mounted over it later, it is no longer
accessible, so journalctl does not find it.

I'm not sure where to go forward rom there, but it looks like our
skeleton is wrong when the init system is systemd.

Any clue or suggestion?

Regards,
Yann E. MORIN.

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[Buildroot] systemd and journald

[Eric Le Bihan]

Hi!

Le Sun, 22 May 2016 14:41:40 +0200,
"Yann E. MORIN" <yann.morin.1998@free.fr> a ?crit :

> So, because our /var/log is a symlink to /tmp , the journal is
> correctly created
> in /tmp/journal/c30ad28b21d444ba9fff7fb25b5454b1/system.journal but
> since another filesystem is mounted over it later, it is no longer
> accessible, so journalctl does not find it.
> 
> I'm not sure where to go forward rom there, but it looks like our
> skeleton is wrong when the init system is systemd.

I haven't played with a systemd-based setup for a while, but I used to fix this with a post-build script [1]. 

There was also a discussion some times ago about the need for a skeleton package per init system [2].

[1] https://github.com/elebihan/buildroot-ext-elb/blob/master/overlays/base-systemd/post-build.sh
[2] http://buildroot-busybox.2317881.n4.nabble.com/How-to-provide-one-default-skeleton-per-init-system-td72124.html

-- 
ELB

[Buildroot] systemd and journald

[Yann E. MORIN]

?ric, All,

On 2016-05-23 10:07 +0200, Eric Le Bihan spake thusly:
> Le Sun, 22 May 2016 14:41:40 +0200,
> "Yann E. MORIN" <yann.morin.1998@free.fr> a ?crit :
> 
> > So, because our /var/log is a symlink to /tmp , the journal is
> > correctly created
> > in /tmp/journal/c30ad28b21d444ba9fff7fb25b5454b1/system.journal but
> > since another filesystem is mounted over it later, it is no longer
> > accessible, so journalctl does not find it.
> > 
> > I'm not sure where to go forward rom there, but it looks like our
> > skeleton is wrong when the init system is systemd.
> 
> I haven't played with a systemd-based setup for a while, but I used to
> fix this with a post-build script [1]. 

Hmm.. that's what maxime told me on IRC, too...

> There was also a discussion some times ago about the need for a
> skeleton package per init system [2].

Right, and it's been there a long time ago...

> [1] https://github.com/elebihan/buildroot-ext-elb/blob/master/overlays/base-systemd/post-build.sh
> [2] http://buildroot-busybox.2317881.n4.nabble.com/How-to-provide-one-default-skeleton-per-init-system-td72124.html

Thanks for the poitners, I'll try to see what I can come up with.

Thanks!

Regards,
Yann E. MORIN.

-- 
.-----------------.--------------------.------------------.--------------------.
|  Yann E. MORIN  | Real-Time Embedded | /"\ ASCII RIBBON | Erics' conspiracy: |
| +33 662 376 056 | Software  Designer | \ / CAMPAIGN     |  ___               |
| +33 223 225 172 `------------.-------:  X  AGAINST      |  \e/  There is no  |
| http://ymorin.is-a-geek.org/ | _/*\_ | / \ HTML MAIL    |   v   conspiracy.  |
'------------------------------^-------^------------------^--------------------'