Ubuntu – Script that starts with boot and auto-restart on failure

bashbootscriptsstartup

I'm trying to write an auto start script that starts on boot and restarts if it crashes. The start on boot is doable by simply adding the script to the

/etc/rc.local

File, however my problem is the auto restart. I thought about exporting the $$ Variable into an external text file before starting the actual script, and using this with another script to check whether that pid still is running or not. My question is now how to check if a specific PID is still running and also if there is a more reliable way to do this.

Best Answer

What your script needs to perform in such a manner is systemd sevice.

An example would be the one below:

[Unit]
Description=My Script


[Service]
Type=forking    
ExecStart=/path/to/script
Restart=on-failure

[Install]
WantedBy=multi-user.target

This can be done in several ways:

Place your script in another location and access it from your systemd service files.
Place the code directly in the systemd service file.

I believe the first option is ideal in your situation. Now once done enable at boot with the normal systemctl commands, such as:

sudo systemctl enable myscript.service
sudo systemctl status myscript.service
sudo systemctl stop myscript.service
sudo systemctl start myscript.service

Sources:

https://www.digitalocean.com/community/tutorials/understanding-systemd-units-and-unit-files

https://www.freedesktop.org/software/systemd/man/systemd.unit.html

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Ubuntu – rc.local is not always executed upon boot

Place the touch on the first line, and make sure it touches a file in a directory where everyone has write access.

Then, log any errors, for example like:

echo -n 255 > /sys/devices/platform/i8042/serio1/serio2/sensitivity 2> /your/log/file
echo level 2 > /proc/acpi/ibm/fan 2> /your/log/file
touch /home/starcorn/Desktop/foo >> /your/log/file 2>&1

rfkill block bluetooth >> /your/log/file 2>&1
exit 0

The >> logfile 2&>1 tells the shell to log error messages to the same file as normal output. The 2> logfile only logs the errors.

What happens with these changes?

Ubuntu – Why is the command in /etc/rc.local not executed during startup

rc.local script exits if any error occurs while executing any of its commands (mention the -e flag in #!/bin/sh -e).

It is possible that some prerequisites are not met when you try to run your commands when rc.local execution takes place, so your command execution fails.

I encountered the same thing while manually setting cpu governor and failing to do so in rc.local. Here's my custom workaround, which uses update-rc.d to make your commands run on startup:

Create a file myscript.sh in directory /etc/init.d with a heading: #!/bin/sh
Put your custom commands as the content
Make it executable: sudo chmod +x /etc/init.d/myscript.sh
Create symlinks for your script for various runlevels: sudo update-rc.d myscript.sh defaults

Also, you could check /etc/network/if-up.d scripts and see if you could trigger your commands when networking starts.

Best Answer

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