Raspberry Pi with multiboot (multiple rootfs)

[ raspberry boot ]

One question that I receive (from my friends, myself and people that install archlinux at 3am) appears every time. How to create a multiboot architecture inside a sdcard for the Raspberry Pi ?

After a boring day doing some unrelated stuff out of home, and with 1h free to do something before sleep and eating (heating my frozen lasagna), why not solving that secular question that follow me ?

I took some time to think about it: maybe doing something related to the archlinux boot section, or with noobs, and maybe with BerryBoot.

With 1h-ish free I did remove all non-trivial ways.

• archlinux: The script will use all the sdcard, changing the scripts will take time.
• noobs: It does not appears to be the correct tool, some investigation shows that.
• BerryBoot: Appears to be the way to go, but it'll take time also to configure everything.

Doing the hard stuff with no sweat

So, the idea now is to break everything and try something new. Use Raspbian image, create a second rootfs partition, change the rootfs in /boot, sounds simple, easy and fast !

1. Download Raspbian (I did everything with Raspbian stretch lite).

2. Burn the sdcard with Etcher (I like dd, but Etcher is so simple!).

3. Use gparted to create a second partition with the same configuration of the /rootfs one ! (rootfs2).

   

4. Make a copy of our old rootfs. sudo cp /mount_point_of_rootfs/* /mount_point_of_rootfs2/* -r

5. Now, with everything ready, we should update the partuuid values of /etc/fstab and /boot/cmdline.txt. (sudo blkid)

   /dev/mmcblk0p1: LABEL="boot" UUID="3725-1C05" TYPE="vfat" PARTUUID="0155ef5b-01"
   /dev/mmcblk0p2: LABEL="rootfs" UUID="fd695ef5-f047-44bd-b159-2a78c53af20a" TYPE="ext4" PARTUUID="0155ef5b-02"
   /dev/mmcblk0p3: LABEL="rootfs2" UUID="3da53eaa-4044-4554-8052-0f8c225f7b8c" TYPE="ext4" PARTUUID="0155ef5b-03"
   

6. With all partitions mounted, update:

   • /boot/cmdline.txt: partuuid of /rootfs to 0155ef5b-02
   • /rootfs/etc/fstab: partuuid of /boot to 0155ef5b-01 and / to 0155ef5b-02
   • /rootfs2/etc/fstab: partuuid of /boot to 0155ef5b-01 and / to 0155ef5b-03

7. To change which rootfs you want to boot, just need to change the suffix of the partuuid in /boot/cmdline.txt.

The 01 suffix is the boot partition (/boot), 02 is our "recovery" partition with 700MB free (/rootfs), and our last and probably the "main" partition with 13GB free is the one with 03 suffix (/rootfs2).

Notes

• This may not work with different kernels because of the initramfs.
• If you want to improve this article, please send a PR in my github !