How to grow partitions using systemd-growfs?

[paulmenzel]

Dear mkosi folks, as with systemd-repart I assume, I need to configure the image myself, if I want this feature. Instead of /etc/fstab using a partition flag bit 59 can be used. Did somebody already integrate that in their mkosi configuration?

[rgilton]

The method I tried was was to put this file in /etc/repart.d/50-root.conf:

[Partition]
Type=root
GrowFileSystem=yes

I was expecting systemd-repart and systemd-growfs to do their magic and grow the root partition and filesystem. Unfortunately neither of those things happened. I think this is because the "first boot" is occurring when mkosi builds the image (i.e. it creates /etc/machine-id, which is what systemd uses to determine if the first boot has occurred), rather than when I ship the resulting image off somewhere else (in my case, libvirt).

If I manually start systemd-growfs-root.service, then the partition and filesystem are successfully resized. I have yet to work out an automated approach though.

[rgilton]

Ok, I think I've figured out that systemd-growfs-root.service is just not configured by default to run on first-boot, or indeed on any boot.

So with the following modifications, the root fs gets resized properly for me:

1. /etc/repart.d/50-root.conf contains the value I wrote in my previous comment.
2. Set systemd-growfs-root.service to:
   a) by WantedBy by multi-user.target
   b) only run on first boot.
   c) be enabled

2(a) and (b) are achieved by this override in /etc/systemd/system/systemd-growfs-root.service.d:

[Unit]
ConditionFirstBoot=true

[Install]
WantedBy=multi-user.target

2(c) is achieved by running systemctl enable systemd-growfs-root.service in the mkosi.finalize script.