Question

Can I set boot parameters for the kernel through the #cloud-config

Posted on June 18, 2023
Configuration Management DigitalOcean Droplets
Asked by cybertrapped

I would like to set kernel parameters through the droplet’s initialization script #cloud-config.

I saw your tutorials to set user related configuration https://www.digitalocean.com/community/tutorials/how-to-use-cloud-config-for-your-initial-server-setup , but I have been unable to find information about to pass configuration setting for the kernel through the #cloud-config script

If this is possible, could you provide me with an example that shows how I would pass boot loader command parameters equivalent to "ignore_loglevel debug log_buf_len=100M "

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KFSys

Site Moderator

• June 19, 2023

Heya @cybertrapped,

You can set the Kernel parameters in the GRUB configuration file and then reboot your Droplet to make the changes take effect.

With that said, yes, you can use cloud-config to update Grub and then reboot your Droplet.

The kernel parameters are typically added in the line starting with GRUB_CMDLINE_LINUX_DEFAULT in the /etc/default/grub file.

Here’s an example cloud-config that would append “ignore_loglevel debug log_buf_len=100M” to your kernel command line:

#cloud-config
write_files:
-   path: /etc/default/grub.d/50-cloudimg-settings.cfg
    content: |
        GRUB_CMDLINE_LINUX_DEFAULT="$GRUB_CMDLINE_LINUX_DEFAULT ignore_loglevel debug log_buf_len=100M"
runcmd:
-   update-grub

This script will create a new file under /etc/default/grub.d/ with the name 50-cloudimg-settings.cfg. The content of the file is GRUB_CMDLINE_LINUX_DEFAULT="$GRUB_CMDLINE_LINUX_DEFAULT ignore_loglevel debug log_buf_len=100M".

It’s important to note that the files in this directory are processed in alphanumeric order, and they modify the environment variables that are used in the main /etc/default/grub file.

The runcmd directive will run update-grub command to regenerate the GRUB configuration file.

On the next reboot, your new kernel parameters will be in effect.