rootless.md

Rootless mode (Experimental)

Requirements:

• runc (May 30, 2018) or later
• Some distros such as Debian and Arch Linux require echo 1 > /proc/sys/kernel/unprivileged_userns_clone
• newuidmap and newgidmap need to be installed on the host. These commands are provided by the uidmap package.
• /etc/subuid and /etc/subgid should contain >= 65536 sub-IDs. e.g. penguin:231072:65536.
• To run in a Docker container with non-root USER, docker run --privileged is still required. See also Jessie's blog: https://blog.jessfraz.com/post/building-container-images-securely-on-kubernetes/

Setting up rootless mode also requires some bothersome steps as follows, but we will soon have automation tool.

Terminal 1:

$ unshare -U -m
unshared$ echo $$ > /tmp/pid

Unsharing mountns (and userns) is required for mounting filesystems without real root privileges.

Terminal 2:

$ id -u
1001
$ grep $(whoami) /etc/subuid
penguin:231072:65536
$ grep $(whoami) /etc/subgid
penguin:231072:65536
$ newuidmap $(cat /tmp/pid) 0 1001 1 1 231072 65536
$ newgidmap $(cat /tmp/pid) 0 1001 1 1 231072 65536

Terminal 1:

unshared# buildkitd

• The data dir will be set to /home/penguin/.local/share/buildkit
• The address will be set to unix:///run/user/1001/buildkit/buildkitd.sock
• overlayfs snapshotter is not supported except Ubuntu-flavored kernel: http://kernel.ubuntu.com/git/ubuntu/ubuntu-artful.git/commit/fs/overlayfs?h=Ubuntu-4.13.0-25.29&id=0a414bdc3d01f3b61ed86cfe3ce8b63a9240eba7
• containerd worker is not supported ( pending PR: containerd/containerd#2006 )
• Network namespace is not used at the moment.

Terminal 2:

$ go get ./examples/build-using-dockerfile
$ build-using-dockerfile --buildkit-addr unix:///run/user/1001/buildkit/buildkitd.sock -t foo /path/to/somewhere