This page is deprecated and not maintained, since cgroup/docker support is built-in now

My Raspberry Pi 3 died. It was used for running Plex server. It was running inside docker before the Pi died. I was looking for replacement. I looked into my basement and I found two Google_Nexus_5_(lg-hammerhead) phones. Then the story began...

Prerequisites

you are fairly familiar with how flashing works, e.g. fastboot stuff.
you've already running postmarketos on your phone
you know what docker is
you know that you are probably gonna remove all the fancy UIs from your phone, and switch to postmarketos-ui-fbkeyboard or some console only mode
you'd better have a LAN connection on your phone rather than wifi

Steps

I can only prove this is working on my phones for now.

1. edit kernel config

NOTE: before you make any change to kernel, always backup ~/.local/var/pmbootstrap/cache_git/pmaports/main/linux-postmarketos-qcom-msm8974/config-postmarketos-qcom-msm8974.armv7

Run

pmbootstrap kconfig edit postmarketos-qcom-msm8974

where qcom-msm8974 is for my Nexus 5. You need to figure out what's for your phone.

You have 2 options to configure the kernel:

a) follow https://wiki.gentoo.org/wiki/Docker#Kernel (which doesn't really apply to kernel 5.9 but I made it)

b) run https://raw.githubusercontent.com/moby/moby/master/contrib/check-config.sh

You can see the changes I made to my kernel config at https://gitlab.com/tigerinus/pmaports/-/commit/d4c1ad862f5485fd9a7577e59b95e97da1b988ae

BTW - I've got a Ugreen USB 2.0 network adapter hooked, so I took the chance and selected Device Drivers => Network device support => <*> USB Network Adapters => <*> ASIX AX88xxx Based USB 2.0 Ethernet Adapters (or whatever adapter you have)

2. build the kernel

pmbootstrap build linux-postmarketos-qcom-msm8974 --force

I had to add --force otherwise it won't build.

If everything is successful, you should find something like below

~/.local/var/pmbootstrap/packages/edge/armv7/linux-postmarketos-qcom-msm8974-5.9.0_rc4-r0.apk

3. install the kernel

Get the linux-postmarketos-qcom-msm8974-5.9.0_rc4-r0.apk copied onto your phone and do

sudo apk add -u linux-postmarketos-qcom-msm8974-5.9.0_rc4-r0.apk

Just in case, I also copied /boot/boot.img-postmarketos-qcom-msm8974 to local as boot.img, boot to bootloader and did

fastboot flash boot boot.img

Reboot the phone and run check-config.sh again to see if anything missing. My experience is you don't need everything enabled.

4. install docker

Boot to your phone, assuming you have a pretty good internet connection, then do

sudo apk add docker

Not only this installs docker, but also an important service containerd.

5. get docker daemon running

Run

sudo service docker start

We are not there yet. This first-time boot is for creating files, directories, group it needs. The docker command won't work because of couple things that have to happen at boot time below.

BTW - If you hate doing sudo docker... everytime, you can optionally add yourself to docker group by