Difference between revisions of "EBC Exercise 21b systemd"

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(systemd: Removed)
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== Running your own service ==
 
== Running your own service ==
  
== systemd ==
 
<pre>
 
beagle$ systemctl
 
UNIT                      LOAD  ACTIVE SUB      JOB DESCRIPTION
 
proc-sys...misc.automount loaded active running      Arbitrary Executable File Formats File System Automount Point
 
sys-devi...et-eth0.device loaded active plugged      /sys/devices/platform/cpsw.0/net/eth0
 
sys-devi...et-usb0.device loaded active plugged      /sys/devices/platform/omap/musb-ti81xx/musb-hdrc.0/gadget/net/usb0
 
sys-devi...cblk0p1.device loaded active plugged      /sys/devices/platform/omap/omap_hsmmc.0/mmc_host/mmc0/mmc0:1234/block/mmcblk0/mmcblk0p
 
sys-devi...cblk0p2.device loaded active plugged      /sys/devices/platform/omap/omap_hsmmc.0/mmc_host/mmc0/mmc0:1234/block/mmcblk0/mmcblk0p
 
sys-devi...mmcblk0.device loaded active plugged      /sys/devices/platform/omap/omap_hsmmc.0/mmc_host/mmc0/mmc0:1234/block/mmcblk0
 
sys-devi...y-ttyO0.device loaded active plugged      /sys/devices/platform/omap/omap_uart.0/tty/ttyO0
 
sys-devi...y-ttyO1.device loaded active plugged      /sys/devices/platform/omap/omap_uart.1/tty/ttyO1
 
sys-devi...y-ttyO2.device loaded active plugged      /sys/devices/platform/omap/omap_uart.2/tty/ttyO2
 
sys-devi...y-ttyO3.device loaded active plugged      /sys/devices/platform/omap/omap_uart.3/tty/ttyO3
 
sys-devi...y-ttyO4.device loaded active plugged      /sys/devices/platform/omap/omap_uart.4/tty/ttyO4
 
sys-devi...y-ttyO5.device loaded active plugged      /sys/devices/platform/omap/omap_uart.5/tty/ttyO5
 
sys-devi...y-ttyS0.device loaded active plugged      /sys/devices/platform/serial8250/tty/ttyS0
 
sys-devi...y-ttyS1.device loaded active plugged      /sys/devices/platform/serial8250/tty/ttyS1
 
sys-devi...y-ttyS2.device loaded active plugged      /sys/devices/platform/serial8250/tty/ttyS2
 
sys-devi...y-ttyS3.device loaded active plugged      /sys/devices/platform/serial8250/tty/ttyS3
 
sys-devi...et-sit0.device loaded active plugged      /sys/devices/virtual/net/sit0
 
sys-devi...ty-tty0.device loaded active plugged      /sys/devices/virtual/tty/tty0
 
sys-devi...ty-tty1.device loaded active plugged      /sys/devices/virtual/tty/tty1
 
sys-devi...y-tty10.device loaded active plugged      /sys/devices/virtual/tty/tty10
 
sys-devi...y-tty11.device loaded active plugged      /sys/devices/virtual/tty/tty11
 
sys-devi...y-tty12.device loaded active plugged      /sys/devices/virtual/tty/tty12
 
sys-devi...ty-tty2.device loaded active plugged      /sys/devices/virtual/tty/tty2
 
sys-devi...ty-tty3.device loaded active plugged      /sys/devices/virtual/tty/tty3
 
sys-devi...ty-tty4.device loaded active plugged      /sys/devices/virtual/tty/tty4
 
sys-devi...ty-tty5.device loaded active plugged      /sys/devices/virtual/tty/tty5
 
sys-devi...ty-tty6.device loaded active plugged      /sys/devices/virtual/tty/tty6
 
sys-devi...ty-tty7.device loaded active plugged      /sys/devices/virtual/tty/tty7
 
sys-devi...ty-tty8.device loaded active plugged      /sys/devices/virtual/tty/tty8
 
sys-devi...ty-tty9.device loaded active plugged      /sys/devices/virtual/tty/tty9
 
-.mount                  loaded active mounted      /
 
dev-mqueue.mount          loaded active mounted      POSIX Message Queue File System
 
etc-machine\x2did.mount  loaded active mounted      /etc/machine-id
 
proc-sys...fmt_misc.mount loaded active mounted      Arbitrary Executable File Formats File System
 
sys-kernel-debug.mount    loaded active mounted      Debug File System
 
tmp.mount                loaded active mounted      Temporary Directory
 
systemd-...d-console.path loaded active waiting      Dispatch Password Requests to Console Directory Watch
 
systemd-...word-wall.path loaded active waiting      Forward Password Requests to Wall Directory Watch
 
avahi-daemon.service      loaded active running      Avahi mDNS/DNS-SD Stack
 
bone101.service          loaded active running      Beaglebone 101 presentation
 
cape.service              loaded active exited        Beaglebone cape support
 
cloud9.service            loaded active running      Cloud9 IDE
 
connman.service          loaded active running      Connection service
 
console-...-start.service loaded active exited        Console System Startup Logging
 
crond.service            loaded active running      Periodic Command Scheduler
 
dbus.service              loaded active running      D-Bus System Message Bus
 
dropbear...:59238.service loaded active running      SSH Per-Connection Server
 
gateone.service          loaded active running      GateOne daemon
 
gdm.service              loaded active running      Gnome Display Manager
 
getty@tty1.service        loaded active running      Getty on tty1
 
leds.service              loaded active exited        Angstrom LED config
 
network-...t-init.service loaded active exited        Start USB Ethernet gadget
 
pvr-init.service          loaded active exited        pvr-init.service
 
remount-rootfs.service    loaded active exited        Remount Root FS
 
serial-g...@ttyO0.service loaded active running      Serial Getty on ttyO0
 
systemd-journald.service  loaded active running      Journal Service
 
systemd-logind.service    loaded active running      Login Service
 
systemd-...s-load.service loaded active exited        Load Kernel Modules
 
systemd-...pi-vfs.service loaded active exited        Remount API VFS
 
systemd-sysctl.service    loaded active exited        Apply Kernel Variables
 
systemd-...-setup.service loaded active exited        Recreate Volatile Files and Directories
 
systemd-...ssions.service loaded active exited        Permit User Sessions
 
timestamp.service        loaded active exited        Timestamping service
 
udev-trigger.service      loaded active exited        udev Coldplug all Devices
 
udev.service              loaded active running      udev Kernel Device Manager
 
udhcpd.service            loaded active running      DHCP server for USB0 network gadget
 
xinetd.service            loaded active exited        xinetd.service
 
avahi-daemon.socket      loaded active listening    Avahi mDNS/DNS-SD Stack Activation Socket
 
dbus.socket              loaded active running      D-Bus System Message Bus Socket
 
dropbear.socket          loaded active listening    dropbear.socket
 
systemd-initctl.socket    loaded active listening    /dev/initctl Compatibility Named Pipe
 
systemd-journald.socket  loaded active running      Journal Socket
 
systemd-shutdownd.socket  loaded active listening    Delayed Shutdown Socket
 
udev-control.socket      loaded active listening    udev Control Socket
 
udev-kernel.socket        loaded active running      udev Kernel Socket
 
basic.target              loaded active active        Basic System
 
getty.target              loaded active active        Login Prompts
 
graphical.target          loaded active active        Graphical Interface
 
local-fs-pre.target      loaded active active        Local File Systems (Pre)
 
local-fs.target          loaded active active        Local File Systems
 
multi-user.target        loaded active active        Multi-User
 
remote-fs.target          loaded active active        Remote File Systems
 
sockets.target            loaded active active        Sockets
 
swap.target              loaded active active        Swap
 
sysinit.target            loaded active active        System Initialization
 
systemd-...es-clean.timer loaded active waiting      Daily Cleanup of Temporary Directories
 
 
LOAD  = Reflects whether the unit definition was properly loaded.
 
ACTIVE = The high-level unit activation state, i.e. generalization of SUB.
 
SUB    = The low-level unit activation state, values depend on unit type.
 
JOB    = Pending job for the unit.
 
 
86 units listed. Pass --all to see inactive units, too.
 
</pre>
 
  
 
{{YoderFoot}}
 
{{YoderFoot}}

Revision as of 16:07, 10 October 2013

thumb‎ Embedded Linux Class by Mark A. Yoder


Traditionally user space initialization has been done using init.d, however recently many distributions have been switching to systemd

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 control groups, supports snapshotting and restoring of the system state, maintains mount and automount points and implements an elaborate transactional dependency-based service control logic.

Here we'll see how to use systemd as an administration and how to create a simple service.

Administration

There are a few simple commands that show what's running under systemd and how to stop and start them. The examples here were inspired by the twenty part series on systemd administration and the three part intro by Carla Schroder

To see what's running, run

beagle$ systemctl
UNIT                        LOAD   ACTIVE SUB       DESCRIPTION
proc-sys...t_misc.automount loaded active waiting   Arbitrary Executable File Fo
sys-devi...tty-ttyO0.device loaded active plugged   /sys/devices/ocp.2/44e09000.
sys-devi...ty-ttyGS0.device loaded active plugged   /sys/devices/ocp.2/47400000.
sys-devi...-net-eth0.device loaded active plugged   /sys/devices/ocp.2/4a100000.
sys-devi...blk0boot0.device loaded active plugged   /sys/devices/ocp.2/mmc.10/mm
sys-devi...blk0boot1.device loaded active plugged   /sys/devices/ocp.2/mmc.10/mm
sys-devi...mmcblk0p1.device loaded active plugged   /sys/devices/ocp.2/mmc.10/mm
sys-devi...mmcblk0p2.device loaded active plugged   /sys/devices/ocp.2/mmc.10/mm
sys-devi...k-mmcblk0.device loaded active plugged   /sys/devices/ocp.2/mmc.10/mm
sys-devi...tty-ttyS0.device loaded active plugged   /sys/devices/platform/serial
sys-devi...tty-ttyS1.device loaded active plugged   /sys/devices/platform/serial
sys-devi...tty-ttyS2.device loaded active plugged   /sys/devices/platform/serial
sys-devi...tty-ttyS3.device loaded active plugged   /sys/devices/platform/serial
sys-module-fuse.device      loaded active plugged   /sys/module/fuse
sys-subs...ices-eth0.device loaded active plugged   /sys/subsystem/net/devices/e
-.mount                     loaded active mounted   /
dev-mqueue.mount            loaded active mounted   POSIX Message Queue File Sys
sys-fs-f...onnections.mount loaded active mounted   FUSE Control File System
sys-kernel-debug.mount      loaded active mounted   Debug File System
tmp.mount                   loaded active mounted   /tmp
systemd-...ord-console.path loaded active waiting   Dispatch Password Requests t
systemd-...ssword-wall.path loaded active waiting   Forward Password Requests to
avahi-daemon.service        loaded active running   Avahi mDNS/DNS-SD Stack
bonescript-autorun.service  loaded active running   Bonescript autorun
bonescript.service          loaded active running   Bonescript server

and so on. Look through the list and see what you recognize. If you make your window bigger you will see more information. Here's how to find more details about a given process.

beagle$ systemctl status bonescript.service
bonescript.service - Bonescript server
         Loaded: loaded (/lib/systemd/system/bonescript.service; static)
         Active: active (running) since Tue 2013-10-08 15:30:10 EDT; 1 day 20h ago
       Main PID: 346 (node)
         CGroup: name=systemd:/system/bonescript.service
       	  `-346 /usr/bin/node server.js

Oct 08 15:30:10 yoder-black-bone systemd[1]: Started Bonescript server.
Oct 08 15:30:16 yoder-black-bone bonescript[346]: [35B blob data]
Oct 08 15:30:16 yoder-black-bone bonescript[346]: - - - [Tue, 08 Oct 2013 19:...
Oct 08 15:30:17 yoder-black-bone bonescript[346]: - - - [Tue, 08 Oct 2013 19:...
Oct 08 15:30:17 yoder-black-bone bonescript[346]: - - - [Tue, 08 Oct 2013 19:...

Stopping and Starting

You can stop a process with

beagle$ systemctl | grep cloud
cloud9.service              loaded active running   Cloud9 IDE
beagle$ systemctl status cloud9
cloud9.service - Cloud9 IDE
         Loaded: loaded (/lib/systemd/system/cloud9.service; enabled)
         Active: active (running) since Fri 2000-01-07 17:46:06 EST; 13 years 9 months ago
       Main PID: 130 (node4)
         CGroup: name=systemd:/system/cloud9.service
       	  `-130 /usr/bin/node4 /usr/share/cloud9/bin/cloud9.js -l 0.0...

Oct 08 15:30:15 yoder-black-bone node4[130]: publish state{"type":"state","p...}
Oct 10 10:51:10 yoder-black-bone node4[130]: uncaught exception:
Oct 10 10:51:10 yoder-black-bone node4[130]: Error: ENOENT, No such file or ...'
Oct 10 10:51:10 yoder-black-bone node4[130]: at Object.statSync (fs.js:400:18)
Oct 10 10:51:10 yoder-black-bone node4[130]: at /usr/share/cloud9/server/clo...7
Oct 10 10:51:10 yoder-black-bone node4[130]: at Array.forEach (native)
Oct 10 10:51:10 yoder-black-bone node4[130]: at StatWatcher.<anonymous> (/us...)
beagle$ systemctl stop cloud9

Now try accessing cloud9 from a web browser (192.168.7.2:3000). It isn't there. You can start it with

beagle$ systemctl start cloud9
beagle$ systemctl status cloud9
cloud9.service - Cloud9 IDE
         Loaded: loaded (/lib/systemd/system/cloud9.service; enabled)
         Active: active (running) since Thu 2013-10-10 11:53:25 EDT; 14s ago
       Main PID: 1470 (node4)
         CGroup: name=systemd:/system/cloud9.service
       	  `-1470 /usr/bin/node4 /usr/share/cloud9/bin/cloud9.js -l 0....

Oct 10 11:53:29 yoder-black-bone node4[1470]: .){2ooooonnnnvnvnvvvvvIIIIIIll...`
Oct 10 11:53:29 yoder-black-bone node4[1470]: -{2oooonnnnnvvvvvvvlIIlllllil=...-
Oct 10 11:53:29 yoder-black-bone node4[1470]: . -."11oonnvvvnvvIIlIlliliiiii....
Oct 10 11:53:29 yoder-black-bone node4[1470]: . -+~!lvvnvIvIIllliiiii|i|||i|....
Oct 10 11:53:29 yoder-black-bone node4[1470]: . ..--~++++++++~+~+~+~+-+-+~+~....
Oct 10 11:53:29 yoder-black-bone node4[1470]: . .  . . .... . . .... .. ... ....
Oct 10 11:53:29 yoder-black-bone node4[1470]: Ajax.org Cloud9 IDE
Oct 10 11:53:29 yoder-black-bone node4[1470]: version 0.6
Oct 10 11:53:29 yoder-black-bone node4[1470]: Project root is: /var/lib/cloud9
Oct 10 11:53:29 yoder-black-bone node4[1470]: Point your browser to http://l...0

Notice the log messages have changed.

Autostart at boot time

You can use enable and disable to make a service start (or not start) at boot time.

beagle$ systemctl disable cloud9
rm '/etc/systemd/system/multi-user.target.wants/cloud9.service'
beagle$ systemctl enable cloud9
ln -s '/lib/systemd/system/cloud9.service' '/etc/systemd/system/multi-user.target.wants/cloud9.service'

Watch out though, if some other service needs the service you disabled, it will start anyway. If you want to stop a service NO MATTER WHAT.

beagle$ ln -s /dev/null /etc/systemd/system/servicename.service
beagle$ systemctl daemon-reload

systemd first looks in /etc/systemd/system and then looks in /lib/systemd/system. The command above places an empty file in /etc/systemd/system, so the real file in /lib/systemd/system is never seen.

Running your own service



thumb‎ Embedded Linux Class by Mark A. Yoder