Difference between revisions of "EBC Exercise 21b systemd"
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'''[Install]''' | '''[Install]''' | ||
'''WantedBy=multi-user.target''' | '''WantedBy=multi-user.target''' | ||
− | I copied the last two line from /lib/systemd/system/cloud9.service since they are needed to start at boot time. Modify the file so it will work for your server. | + | I copied the last two line from /lib/systemd/system/cloud9.service since they are needed to start at boot time. Modify the file so it will work for your server. Make sure to modify 'Description' as well or your service will confuse itself with the original bonescript.service. |
There is one other thing you have to add to the file. When node.js runs it needs to know where to find its modules. There is an environment variable that says where | There is one other thing you have to add to the file. When node.js runs it needs to know where to find its modules. There is an environment variable that says where |
Revision as of 20:55, 11 October 2013
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.
Contents
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.
Stopping no matter what
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
If you check in exercises/realtime you find boneServer.js a server for some demos. You run it with:
beagle$ cd exercises/realtime beagle$ ./boneServer.js Listening on 8080 info - socket.io started
Now point a browser to 192.168.7.2:8080. You'll see a list of demos served up by boneServer.js. Suppose you want the boneServer to automatically start every time the the Beagle boots. Here is how to do it.
We need to create a service file and the quickest way is to find one that does similar things.
beagle$ systemctl | grep bone bonescript-autorun.service loaded active running Bonescript autorun bonescript.service loaded active running Bonescript server bonescript.socket loaded active running bonescript.socket
I see a couple of bonescript servers that look promising.
beagle$ systemctl status bonescript bonescript.service - Bonescript server Loaded: loaded (/lib/systemd/system/bonescript.service; static) Active: active (running) since Sun 2000-01-09 15:07:55 EST; 13 years 9 months ago Main PID: 357 (node) CGroup: name=systemd:/system/bonescript.service `-357 /usr/bin/node server.js Jan 09 15:07:55 yoder-black-bone systemd[1]: Starting Bonescript server... Jan 09 15:08:04 yoder-black-bone bonescript[357]: [35B blob data] Jan 09 15:08:05 yoder-black-bone bonescript[357]: - - - [Sun, 09 Jan 2000 20:...
Looks like the file is in /lib/systemd/system/bonescript.service copy it to a handy place and take a look.
beagle$ cp /lib/systemd/system/bonescript.service boneServer.service beagle$ cat boneServer.service [Unit] Description=Bonescript server [Service] WorkingDirectory=/usr/lib/node_modules/bonescript ExecStart=/usr/bin/node server.js SyslogIdentifier=bonescript [Install] WantedBy=multi-user.target
I copied the last two line from /lib/systemd/system/cloud9.service since they are needed to start at boot time. Modify the file so it will work for your server. Make sure to modify 'Description' as well or your service will confuse itself with the original bonescript.service.
There is one other thing you have to add to the file. When node.js runs it needs to know where to find its modules. There is an environment variable that says where
beagle$ echo $NODE_PATH /usr/lib/node_modules
You need to add a line to the service file that set this environment variable. Look at the other files in /lib/systemd/system to see how this is done. (Hint: grep Env *).
Once your BoneServer.service file is ready, copy it to the right place
beagle$ cp boneServer.service /lib/systemd/system
and start the server
beagle$ systemctl start boneServer
Point your browser to 192.168.7.2:8080 and see if it works.
To make it work after rebooting
beagle$ systemctl enable boneServer ln -s '/lib/systemd/system/boneServer.service' '/etc/systemd/system/multi-user.target.wants/boneServer.service'
Notice it copies your file to another place. Try rebooting and see if it works.
Embedded Linux Class by Mark A. Yoder