Debian based docker:dind-rootless fails to start with error

[dg424]

Hi,

Please see the discussion here - https://github.com/moby/moby/issues/42910#issue-1016724099. With the help of one of the contributors, I was able to create a debian based rootless image. Everything seems ok, except that the following error pops up on startup:

[rootlesskit:parent] error: failed to setup UID/GID map: newuidmap 42 [0 1000 1 1 100000 65536 65537 100000 65536] failed: newuidmap: write to uid_map failed: Invalid argument

@AkihiroSuda Thought I'd post this here since it no longer seems relevant to moby and they might not take any further action on the issue.

[AkihiroSuda]

Please make sure to run the image with --privileged

[dg424]

Hi Akihiro, Yes, here is the run:

$ docker run --rm -it --privileged --name dind-rootless -e DOCKER_TLS_CERTDIR="" -p 2375:2375 dind-rootless-debian
[rootlesskit:parent] error: failed to setup UID/GID map: newuidmap 32 [0 1000 1 1 100000 65536 65537 100000 65536] failed: newuidmap: write to uid_map failed: Invalid argument
: exit status 1

[dg424]

I posted in Debian's shadow project and this is their response - https://github.com/shadow-maint/shadow/issues/424#issuecomment-939528091

[dg424]

See here - https://github.com/shadow-maint/shadow/issues/424#issuecomment-945881764. Had to comment out the following lines from this part of the rootless Dockerfile - https://github.com/docker-library/docker/blob/master/20.10/dind-rootless/Dockerfile#L19 and line 20. Debian Bullseye rootless boots up now.