How to automatically start services with systemd in Yocto

[dougbailey]

I am upgrading a product I have developed to the latest iMX6 BSP that is using Yocto Morty. One big change with the Morty based BSP is the use of Systemd in place of System V Init files.

I read that systemd is supposed to be backaward compatible with the SysV Init files but I do not see this occur. I see that the generated service files are created but the services themselves are not started at boot up.

To get around this, I am regenerating the init files using "*.service" files handled by Systemd. I can generate the files but I need to find a way to specifiy the services that start at bootstrap from the Yocto recipes. I can do it by creating a symlink to the service file from /etc/systemd/system/multi-user.target.wants/ directory. However, I read that manually creating these symlinks is not suggested.

What is the preferred way within Yocto to create systemd service files that are automatically activated at boot?

Regards 

Doug Bailey

[gusarambula]

Hello Doug Bailey,

There are some documents online that may be of help, like the following thread on a third-party forum. I hope it helps!

https://stackoverflow.com/questions/45614578/enable-systemd-services-using-yocto

Regards,

[dougbailey]

Thanks for the information.  It's a big help. 

[ryanpabis]

Did you ever get this to work?  I am having the same problem.  The only way I can get my services to start at boot is by creating the symlink.  Even after following the link posted by gusarambula

[dougbailey]

I ended up using a symlink when I wanted to force the startup in the build process.  

I added the following into my do_install function: 

if ${@bb.utils.contains('DISTRO_FEATURES','systemd','true','false',d)}; then
    install -d ${D}/etc/systemd/system/multi-user.target.wants
    install -m 644 ${WORKDIR}/resetswx.service ${D}/etc/systemd/system/resetswx.service
    ## Add following link if you want auto start of service
    ## ln -s /etc/systemd/system/resetswx.service ${D}/etc/systemd/system/multi-user.target.wants/resetswx.service

fi 

[ryanpabis · Accepted solution]

Thanks Doug.  Not sure exactly what fixed it for me but this is what I did and it work.

NOTE: Like many others I had a sysvinit script and then let the systemd-sysv-generator create a wrapper for me which I called dl-mgr.service.  This service starts and stops the dl-mgr.sh script.  You can find these files in (/run/systemd/generator.late/) if you don't have a .service file yet.

SRC_URI = "file://dl-mgr.sh \
                     file://dl-mgr.service \"

inherit update-rc.d systemd

SYSTEMD_PACKAGES = "${PN}"
INITSCRIPT_PACKAGES = "${PN}"

SYSTEMD_SERVICE_${PN} = "dl-mgr.service"

I then added this to my do_install section

install -d ${D}${libexecdir}
install -m 0755 ${WORKDIR}/dl-mgr.sh ${D}${libexecdir}/dl-mgr.sh
install -d ${D}${systemd_system_unitdir}
install -m 0644 ${WORKDIR}/dl-mgr.service ${D}${systemd_system_unitdir}

As well as this to the end of the .bb file

FILES_${PN} += "${libexecdir}/dl-mgr.sh"
FILES_${PN} += "${systemd_system_unitdir}/dl-mgr.service"

And then finally, i updated my dl-mgr.service (the one that was autogenerated) to include this.

ExecStart=/usr/libexec/dl-mgr.sh start
ExecStop=/usr/libexec/dl-mgr.sh stop

[Install]

WantedBy=multi-user.target

[Sourabh1107]

Hello @ryanpabis  thanks for the solution. I am trying to achieve the same to start my custom script during boot-up. If I have 2 scripts to be executed once rootfs is mounted or during boot-up how should I include 2 files in image recipe? Should I create 2 separate systemd service files? Can you please let me know how to do this? Assuming script names are custom-script1.sh and custom-script2.sh

Your help will be much appreciated.

Thanks in advance.

[la_basco]

I believe the important lines related to enabling the service at startup -- that made your recipe work are:

1.) in your recipe:
inherit update-rc.d systemd 

2.) in your service file

[Install]

WantedBy=multi-user.target


Explanation:
1. This line in the recipe, particularly, inherit systemd, makes use of the systemd.bbclass located in poky/meta/classes where the default directive is to enable services as seen from the lines:

# Whether to enable or disable the services on installation.
SYSTEMD_AUTO_ENABLE ??= "enable"

2. This line is important because in the process of enabling the service, it specifies -- in what systemd target directory the symlink will be installed. In this case, the symlink should be in etc/systemd/system/multi-user.target.wants directory.

[dougbailey]

Whereas my solution is more of a hack, this looks like a better way to implement the service. 

Thanks for posting this.  I will use it in the future.