systemd
systemd is a modern sysvinit & RC replacement for Linux systems. It is supported in Gentoo as an alternate init system.
Contents |
Installation
Prerequisites: kernel
systemd makes use of many modern Linux kernel features. Right now, the lower bound on kernel version is set in the ebuild to 2.6.38. In addition to that, the following kernel configuration options should be enabled:
General setup --->
[*] Control Group support
Device Drivers --->
Generic Driver Options --->
[*] Maintain a devtmpfs filesystem to mount at /dev
File systems --->
[*] Filesystem wide access notification
<M> Kernel automounter version 4 support (also supports v3)
Networking support --->
Networking options --->
TCP/IP networking --->
<M> The IPv6 protocol
Prerequisites: filesystem
/run directory
The /run directory is used by systemd (and some applications) as a non-persistent storage for runtime data like pidfiles, sockets and state files.
The systemd ebuild will create /run directory itself. However, please note that this change will trigger automatic mounting of it in OpenRC as well, and may trigger using it by different software packages.
/etc/mtab symlink
Upstream suggests that the /etc/mtab file should be a symlink to /proc/self/mounts. This is not obligatory and can create problems with mount -o user and NFS mounts.
To create the symlink:
root # ln -sf /proc/self/mounts /etc/mtab/etc/machine-id
Often systemd guides mention creating the file /etc/machine-id as a global replacement for the D-Bus specific /var/lib/dbus/machine-id. In Gentoo this is already done in the sys-apps/dbus ebuild.
Installing
Installing systemd is as simple as emerging sys-apps/systemd.
root # emerge --ask sys-apps/systemdEnabling
Before doing this configure systemd first.
In order to run systemd, you have to switch the init executable kernel (or your initramfs) uses.
With simple kernels, the init=/bin/systemd argument should be added to the kernel command-line. An example excerpt from grub.conf would look like:
title=Gentoo with systemd root (hd0,0) kernel /vmlinuz root=/dev/sda2 init=/bin/systemd
When using initramfs, other command-line argument will be needed. For example, genkernel uses real_init= there:
title=Gentoo with systemd root (hd0,0) kernel /my-genkernel... root=/dev/hda2 real_init=/bin/systemd initrd /initramfs-genkernel...
Configuration
System configuration
systemd comes with some degree of OpenRC compatibility, so it will gracefully read most of the base system options from its files. This includes the following files:
- /etc/conf.d/hostname for hostname,
- /etc/profile.env for locale (created by env-update from /etc/env.d),
- /etc/rc.conf for the unicode console setting,
- /etc/conf.d/consolefont for the console font settings,
- /etc/conf.d/keymaps for the keymap setting (but only the actual keymap).
Additionally, the following configuration directories are both used by OpenRC and systemd:
- /etc/modules-load.d,
- /etc/sysctl.d,
- /etc/binfmt.d (since OpenRC-0.9.4).
Alternatively, you can migrate your system to use Native systemd configuration files. Bear in mind that upstream has made it clear that at some point in the future it will stop supporting configuration files for specific distributions, and it will only support the native systemd configuration files. If you plan to use systemd exclusively, please use its native configuration files.
Listing available services
All global service files are installed in /lib/systemd/system or /usr/lib/systemd/system. Thus, the simplest way of looking up available service units is listing that directory:
root # ls /lib/systemd/system
acpid.service runlevel2.target
alsa-restore.service runlevel2.target.wants
alsa-store.service runlevel3.target
autovt@.service runlevel3.target.wants
avahi-daemon.service runlevel4.target
avahi-daemon.socket runlevel4.target.wants
avahi-dnsconfd.service runlevel5.target
basic.target runlevel5.target.wants
...
The following file suffixes are of interest:
- .service - plain service files (e.g. ones just running a daemon directly),
- .socket - socket listeners (much like inetd),
- .path - filesystem triggers for services (running services when files change etc.).
Alternatively, systemctl tool can be used to list all services (including implicit ones):
root # systemctl --all --fullAnd finally the systemadm graphical tool can be used. It can be installed with the sys-apps/systemd-ui package.
Installing custom service files
Any custom service files should be copied to the /etc/systemd/system directory. The /lib/systemd/system directory is reserved for service files installed by ebuilds.
Enabling and disabling services
The usual way of enabling a service is using
root # systemctl enable foo.serviceServices can be disabled likewise:
root # systemctl disable foo.serviceThese commands enable services using their default name in default target (both specified in Install section of the service file). However, sometimes services either don't provide that information or you want to use another name/target.
Enabling a service under a custom name
This is especially a case for template services -- services in which part of the name following @ (at sign) is used as a parameter to the service. This is often used to specify the terminal on which getty will run.
To enable a service under custom name, you have to create a symlink to the service file in correct /etc/systemd/system/*.wants directory. The name of that directory can either specify a target or another service which will depend on the new one.
For example, to enable stand-alone net-wireless/wpa_supplicant on wlan0, type:
root # ln -s /lib/systemd/system/wpa_supplicant@.service /etc/systemd/system/multi-user.target.wants/wpa_supplicant@wlan0.serviceTo disable the service, just remove the symlink:
root # rm /etc/systemd/system/multi-user.target.wants/wpa_supplicant@wlan0.serviceNative systemd configuration files
systemd supports a few system configuration files to set the most basic system details.
/etc/hostname
A trivial file containing the system hostname. Replaces /etc/conf.d/hostname.
frobnicator
/etc/vconsole.conf
Simple configuration file specifying console font and keymap. Replaces /etc/conf.d/consolefont and /etc/conf.d/keymaps, yet it doesn't support all features of those init.d scripts.
KEYMAP=pl2 FONT=LatArCyrHeb-16 # example: German keyboard and console KEYMAP=de-latin1 FONT=latarcyrheb-sun16
/etc/locale.conf
In systemd, locale settings are stored in /etc/locale.conf. The file supports same syntax as shell locale variables, so you can basically rename /etc/env.d/02locale or a similar file.
LANG="pl_PL.UTF-8" LC_ALL="pl_PL.UTF-8"
systemd-logind & pam_systemd
systemd intends to provide an integrated ConsoleKit replacement called logind. Some applications (like net-misc/networkmanager and sys-auth/polkit) provide support for it through USE=systemd. Please note that this flag usually disables ConsoleKit support as well and thus packages may stop working as expected if the procedure described below is not fulfilled.
In order to enable session tracking for systemd-logind, you have to enable the pam_systemd PAM module first.
# ... session optional pam_motd.so motd=/etc/motd session optional pam_mail.so'''session optional pam_systemd.so'''
Except for tracking user logins (like ConsoleKit does), this will cause all user processes to belong to a cgroup. You can add controllers=... to provide additional cgroup controllers (like cpu for CPU load balancing). You can also add kill-session-processes=1 to ensure that all processes spawned by user are killed on logout. For more information, take a look at man pam_systemd.
Note: A previous version of this page advised you to modify /etc/pam.d/system-login, instead of system-auth. This is not correct, as services such as kdm (PAM files kde and kde-np) or gdm will include system-auth directly, without going via system-login.
Services
Native services
Some of Gentoo packages already install systemd unit files. For these services, it is enough to enable them. A quick summary of packages installing unit files can be seen on systemd eclass users list.
The following table lists systemd services matching OpenRC ones:
| Gentoo package | OpenRC service | systemd unit | Notes |
|---|---|---|---|
| sys-apps/openrc | bootmisc | systemd-tmpfiles-setup.service | always enabled, uses tmpfiles.d |
| consolefont | systemd-vconsole-setup.service | always enabled, uses vconsole.conf | |
| devfs | |||
| dmesg | |||
| fsck | fsck*.service | pulled in implicitly by mounts | |
| functions.sh | See note | bug #373219 | |
| hostname | (builtin) | /etc/hostname | |
| hwclock | |||
| keymaps | systemd-vconsole-setup.service | always enabled, uses vconsole.conf | |
| killprocs | |||
| local | |||
| localmount | local-fs.target | actual units are created implicitly from fstab | |
| modules | systemd-modules-load.service | always enabled, uses /etc/modules-load.d/*.conf | |
| mount-ro | |||
| mtab | |||
| net.lo | |||
| netmount | remote-fs.target | ||
| network | |||
| numlock | |||
| procfs | (builtin) | ||
| root | remount-rootfs.service | ||
| savecache | n/a | OpenRC internals | |
| staticroute | |||
| swap | swap.target | actual units are created implicitly from fstab | |
| swclock | |||
| sysctl | systemd-sysctl.service | sysctl.conf and sysctl.d/ | |
| sysfs | (builtin) | ||
| termencoding | systemd-vconsole-setup.service | always enabled, uses vconsole.conf | |
| urandom | systemd-random-seed-load.service | ||
| systemd-random-seed-save.service | |||
| app-admin/rsyslog | rsyslog | rsyslog.service | |
| media-sound/alsa-utils | alsasound | alsa-store.service | (enabled by default) |
| alsa-restore.socket | (enabled by default) | ||
| net-misc/dhcpcd | dhcpcd | dhcpcd.service | |
| net-misc/openssh | sshd | sshd.service | runs sshd as a daemon |
| sshd.socket | runs sshd on a inetd-like basis (for each incoming connection) | ||
| net-misc/wpa_supplicant | wpa-supplicant | wpa_supplicant.service | D-Bus controlled daemon (e.g. for NetworkManager) |
| wpa_supplicant@.service | interface-specific wpa_supplicant (used like wpa_supplicant@wlan0.service) | ||
| net-print/cups | cupsd | cups.service | classic on-boot start up service |
| cups.socket | socket and path activation (cups only started on-demand) | ||
| cups.path | |||
| net-wireless/bluez | bluetooth | bluetooth.service | |
| sys-apps/dbus | dbus | dbus.service | |
| dbus.socket | |||
| sys-apps/irqbalance | irqbalance | irqbalance.service | supports daemon mode only |
| sys-fs/udev | udev | udev.service | |
| udev-mount | (builtin) | /dev is mounted as tmpfs | |
| udev-postmount | udev-trigger.service | ||
| udev-settle.service | |||
| sys-power/acpid | acpid | acpid.service | |
| x11-apps/xdm | (xdm) | xdm.service | OpenRC uses common xdm init.d installed by x11-base/xorg-server |
OpenRC services
Although systemd originally intended to support running old init.d scripts, that support is not suited well for a dependency-based RC like OpenRC and thus is completely disabled on Gentoo. OpenRC provides additional measures to ensure that init.d scripts can't be run when OpenRC was not used to boot the system (otherwise the results would be unpredictable).
