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Running Ubuntu 18.04 LTS. I've put a script in the following location:

/usr/share/initramfs-tools/scripts/init-bottom/dothis

dothis is set as +x. I've run sudo update-initramfs -u which appears to update the initramfs contents just fine. I've looked at /boot/grub/grub.cfg and see the expected initrd file configured.

Running lsinitramfs on the file DOES show the script as having been added.

I cannot however find any evidence that dothis is being run on boot. As per documentation online, the root filesystem SHOULD be in place by the time the /init-bottom scripts are run, which should be the only thing required for my 'hello world' to work, as it outputs to a file on the root file system.

Is there some other step that needs to be done in order to get this script to run, or show whether it's being run? I've tried to simply output text to a file in /tmp but this is not showing up either.

iluomo
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1 Answers1

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Since you did not provide more details, I have to guess. Does your dothis script write to /tmp inside the initramfs? The root file system is mounted at /root and the initramfs uses switch_root to switch to it (as last step of the initramfs). Then all files written to /tmp are lost. If you let your script write to /root/root/log, this file will appear in /root/log on the booted system.

To further debug your issue, you can boot your system with the kernel parameter break=bottom. Then you get a shell where you can run your script manually. For even faster debug cycles, you can use a virtual machine.

Benjamin Drung
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