GitLab on Strato VServer: Resource temporarily unavailable

reproduce.sh

$ apt-get update && apt-get upgrade -y

$ uname -a
Linux 4.9.0 #1 SMP Mon Mar 16 15:39:59 MSK 2020 x86_64 GNU/Linux

# Install docker based on these instruction https://docs.docker.com/engine/install/debian/
$ apt-get install -y \
    apt-transport-https \
    ca-certificates \
    curl \
    gnupg-agent \
    software-properties-common
    
$ curl -fsSL https://download.docker.com/linux/debian/gpg | apt-key add -
$ add-apt-repository \
   "deb [arch=amd64] https://download.docker.com/linux/debian \
   $(lsb_release -cs) \
   stable"
$ apt-get update && apt-get install -y docker-ce

$ docker --version
Docker version 19.03.8, build afacb8b7f0

$ lsb_release -a
No LSB modules are available.
Distributor ID:	Debian
Description:	Debian GNU/Linux 9.12 (stretch)
Release:	9.12
Codename:	stretch

$ docker run --rm -p 8080:80 gitlab/gitlab-ce:12.9.4-ce.0

Might be a bit late, but for all who're interested.
It's the Numproc which are the problem. As is with all containerized servers there is a limit on how many processes you can run.
In your case the limit is 400 which is absurdly low! For comparison I have another vps with another company and there my limit is 131072.

I only stumbled upon this problem bc I got the 25 year deal from Strato, good thing I cancelled.