Configuring partitions

Kairos configuration mechanism for partitions is based on the cloud-config file given during installation to override the default values set by the installer.

We allow certain flexibility in the sizes and filesystems used for the default install and allow to create extra partitions as well.

For example, the following cloud-config will make the oem partition have a size of 512Mb and an ext4 filesystem, recovery with a size of 10000Mb and a ext4 filesystem, while leaving the rest of the partitions to their default sizes and filesystems.


  device: "/dev/sda"
  auto: true
      size: 512
      fs: ext4
      size: 10000
      fs: ext4

The partitions that can be configured are: oem, recovery, state and persistent.

And the following config will leave the default partitions as is, but create 2 new extra partitions with the given sizes, filesystems and labels:


  device: "/dev/sda"
  auto: true
    - name: first_partition
      size: 512
      fs: ext3
    - name: second_partition
      size: 100
      fs: ext2
      label: PARTITION_TWO

Only one partition can expand to the rest of the disk. Either persistent or one of the extra-partitions. In case you want the latter, you need to specify the size of persistent to a fixed value.

An example of this would be as follows:


  device: "/dev/sda"
  auto: true
      size: 500
    - name: big_partition
      size: 0
      fs: ext3

Note that there are some caveats in the extra partitions setup:

  • Only size, fs, name and label are used for the partition creation, the name is currently used for the partition label.
  • If a partition has no fs set, the partition will be created, but it will not be formatted.
  • No mounting of any type is done during installation to the extra partitions. That part should be done on the stages of the cloud-config manually, with something like the following step:
    - name: "Mount PARTITION_TWO under /opt/extra"
        - mkdir -p /opt/extra
        - mount -o rw /dev/disk/by-label/PARTITION_TWO /opt/extra

Manual partitioning

In some cases, it’s desired that the user has full control over the partitioning of the disk. This can be achieved by setting the no-format option to true and making sure the disk is prepared with the desired partitions before running the installer.

Here is an example config that instructs the installer to use the “second” disk (/dev/vdb) and makes sure the disk is prepared with the desired partitions:


  no-format: true
  auto: false
  poweroff: false
  reboot: false

  - name: "kairos"
    passwd: "kairos"

  - if:  '[ -e "/dev/vdb" ]'
    name: "Create partitions"
      - |
        parted --script --machine -- "/dev/vdb" mklabel gpt
        # Legacy bios
        sgdisk --new=1:2048:+1M --change-name=1:'bios' --typecode=1:EF02 /dev/vdb        
        path: "/dev/vdb"
        # For efi (comment out the legacy bios partition above)
        #- fsLabel: COS_GRUB
        #  size: 64
        #  pLabel: efi
        #  filesystem: "fat"
        - fsLabel: COS_OEM
          size: 64
          pLabel: oem
        - fsLabel: COS_RECOVERY
          size: 8500
          pLabel: recovery
        - fsLabel: COS_STATE
          size: 18000
          pLabel: state
        - fsLabel: COS_PERSISTENT
          pLabel: persistent
          size: 0
          filesystem: "ext4"

For more information about the full config available for partitions and extra partitions see the full cloud-config page

Last modified April 15, 2024: Document custom partitioning (a199e0a)