I'm seeing this:

# docker pull postgres
Using default tag: latest
latest: Pulling from library/postgres
Digest: sha256:28b4a1b0d3ae9b38a16c97a4e655bdc13496a304d1a241c531ac1efc2faa7230
Status: Image is up to date for postgres:latest
# docker run postgres
error: failed switching to "postgres": function not implemented

This is a 32-bit image running on a 32-bit Arch Linux system (https://archlinux32.org/). Although, if I try to pull the same image (actually postgres@sha256:0ce7cf6e460f486f5f9f0ae16ca5504b5e8aa468fdb6e27caa30f38a8ccf2874 to get the 32-bit one) to an x86_64 Arch system it still has the same problem.

# uname -a
Linux router.lan 4.19.4-arch1-1.0-ARCH #1 SMP PREEMPT Mon Nov 26 10:55:08 CET 2018 i686 GNU/Linux

I think the problem is in gosu; if I copy the gosu binary out of the container, and run it outside of Docker, I see the same error.

# ./gosu root true
error: failed switching to "root": function not implemented

gosu is making a setuid syscall which is returning ENOSYS. I'm not sure why.

Can someone reproduce the problem?