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systemd - system and service manager

Introduction

systemd is a system and service manager for Linux, compatible with SysV and LSB init scripts. systemd provides aggressive parallelization capabilities, uses socket and D-Bus activation for starting services, offers on-demand starting of daemons, keeps track of processes using Linux cgroups, supports snapshotting and restoring of the system state, maintains mount and automount points and implements an elaborate transactional dependency-based service control logic. It can work as a drop-in replacement for sysvinit.

Installation

Currently v11 is available from experimental and v13 is being worked on. systemd requires latest upstream version of dbus, means you need dbus >=1.4.0, which can also be found in experimental. You have to enhance your sources.list and add experimental Distribution.

To install systemd (and dbus) from experimental:

# apt-get update
# apt-get install -t experimental dbus systemd

You also need a kernel with the following options enabled:

Since v8 the cgroupfs is mounted at /sys/fs/cgroup. This requires a Linux kernel >= 2.6.36 or a backport of this patch.

Debian Linux kernels (>= 2.6.32-23) are suitable.

Debian packages with native systemd support

dbus

(>=1.4.0-1)

experimental

supports socket activation

rsyslog

(>=5.7.1-1)

experimental

supports socket activation, run "systemctl enable rsyslog.service"

hal

(>=0.5.14-4)

experimental

supports D-Bus activation

consolekit

(>=0.4.3-1)

unstable

supports D-Bus activation

avahi

(>=0.6.28-1)

experimental

avahi-daemon: supports socket and D-Bus activation, avahi-dnsconfd: started by multi-user.target. Run "systemctl enable avahi-daemon.service" resp. "systemctl enable avahi-dnsconfd.service".

EXAMPLE (here for rsyslog, enable service after installation from Debian/experimental):

# systemctl enable rsyslog.service
Output:
ln -s '/lib/systemd/system/rsyslog.service' '/etc/systemd/system/multi-user.target.wants/rsyslog.service'
ln -s '/lib/systemd/system/rsyslog.socket' '/etc/systemd/system/sockets.target.wants/rsyslog.socket'

Known Issues and Workarounds

Issue #1: sysvinit vs. systemd-sysv

sysvinit is the current default init-system in Debian and is flagged as an "Essential" package. This means the package management tools will refuse to remove or replace the package unless forced. Also on dist-upgrades essential packages are preferred and will be re-installed. For more Details see chapters "3.8 Essential packages" and "5.6.9 Essential"

The systemd-sysvinit package ships /sbin/init (as a symlink to /bin/systemd) and therefore conflicts with the sysvinit package.

Workaround #1: Do not install systemd-sysv, enhance grub-line (Kernel command line) by "init=/bin/systemd". For a grub2 persistent solution (requires an update-grub to refresh /boot/grub/grub.cfg):

# $EDITOR /etc/default/grub
GRUB_CMDLINE_LINUX_DEFAULT="quiet init=/bin/systemd" <--- Change this line

# update-grub

Workaround #2: Install systemd-sysv and put package "on hold".

The problem with "Essential flag" needs some discussion with the sysvinit maintainer.

Issue #2: agetty vs. getty

util-linux-ng has /sbin/agetty, Debian has renamed agetty to getty in its util-linux package (will be fixed for wheezy by Debian maintainer) (603786)

Issue #3: libnotify-0.7

Upstream systemd >=v12 requires libnotify 0.7 - this needs a revert as it is not available in Debian yet (603635)

The full error-message in dmesg:

[    5.784886] systemd[1]: /etc/mtab is not a symlink or not pointing to /proc/self/mounts. This is not supported anymore. Please make sure to replace this file by a symlink to avoid incorrect or misleading mount(8) output.

Workaround: 1. Create required symlink 2. Mask mtab and udev-mtab services

# ln -sf /proc/self/mounts /etc/mtab
# ls -l /etc/mtab
Output:
lrwxrwxrwx 1 root root 17 23. Nov 11:31 /etc/mtab -> /proc/self/mounts <--- Created new symlink

# ln -s /dev/null /etc/systemd/system/mtab.service      <--- Mask mtab.service
# ln -s /dev/null /etc/systemd/system/udev-mtab.service <--- Mask udev-mtab.service

# ls -l /etc/init.d/*mtab* <--- Original *mtab* init-scripts
Output:
-rwxr-xr-x 1 root root 3649 22. Mär 2010  /etc/init.d/mtab.sh
-rwxr-xr-x 1 root root 1153 12. Jul 01:20 /etc/init.d/udev-mtab

Debugging systemd

Sometimes it is necessary to investigate why systemd hangs on startup.

EXAMPLE: When building a first v15 package a lot of people fell into the "fsck -l pitfall" (see Known Issues). Result: systemd-fsck gave back error-code 16 and got into maintenance mode (yay!).

Solution #0: Remove "quiet" from Kernel command line (so called "cmdline" or "grub line")

Solution #1: Increase verbosity via cmdline: Add "systemd.log_target=kmsg systemd.log_level=debug"

Of course you can have a "temporary" persistent solution:

[ /etc/default/grub ]
GRUB_CMDLINE_LINUX="systemd.log_target=kmsg systemd.log_level=debug" <--- Add here (by uncommenting you can easily switch to debug)

update-grub

In addition enhance cmdline with "systemd.sysv_console=1" (0: disabled, 1: enabled).

Solution #2: Increase verbosity via /etc/systemd/system.conf

LogLevel=debug           <--- Uncomment this line and use "debug" (default: commented and "info")
LogTarget=syslog-or-kmsg <--- Uncomment this line (default: commented)
SysVConsole=yes          <--- Uncomment this line (default: commented)

HINT: "man system" and "man systemd.conf" (Note: File is system.conf vs. man-page system*d*.conf)

NOTE on ?LogLevel (see systemd(1) and systemd.conf(5)):

"Set log level. As argument this accepts a numerical log level or the well-known syslog(3) symbolic names (lowercase): emerg, alert, crit, err, warning, notice, info, debug."

Use native mount

With v12 or later you can use native (means systemd's) mount and fsck facility by activating it in /etc/systemd/system.conf.

# egrep 'MountAuto|SwapAuto' /etc/systemd/system.conf
Output:
MountAuto=yes
SwapAuto=yes

If you use LVM and your swap partition is on a LV, you need to use the actual device (/dev/dm-X) in /etc/fstab until the lvm2 package has been updated to properly work together with udev (603710)

Who is who?

Maintainer of the systemd package is Tollef Fog Heen (Mithrandir). Currently, it's discussed to get Michael Biebl (mbiebl) as co-maintainer. Michael and Sedat Dilek (dileks) contributed to the initial version of this wiki.

Where to get help?

As systemd is a very young project (see [1]), we would appreciate to use the existing upstream infrastructure like mailing-list [2], IRC and read Lennart's blog [3], etc. for following the development. Most people interested in systemd development (from diverse distributions) and Debian-specific packaging are around on IRC: #systemd (irc.freenode.net). Anyway, Debian-specific bugs should be sent to Debian-BTS (for example use report-bug tool).

  1. http://0pointer.de/blog/projects/systemd.html

  2. http://lists.freedesktop.org/mailman/listinfo/systemd-devel

  3. http://0pointer.de/blog/

Known Bugs and Bug Tracking Systems

TODO

Future plans

Resources