This article introduces how to install docker in the docker Ubuntu container, so that you can create a container in the container and realize the matryoshka doll!
1. Start and enter the docker Ubuntu container
root@ubuntu20:~# docker run -itd --name ubuntu --privileged --cap-add=NET_ADMIN ubuntu:20.04
350983744ebfbc2d7828ef24256b7b5a7d4ce4dd97e083e173c10f2dca4fa097
root@ubuntu20:~# docker exec -it ubuntu bash
root@350983744ebf:/#
2. Replace software source
root@350983744ebf:/# sed -i s@/archive.ubuntu.com/@/mirrors.aliyun.com/@g /etc/apt/sources.list
root@350983744ebf:/# sed -i s@/security.ubuntu.com/@/mirrors.aliyun.com/@g /etc/apt/sources.list
root@350983744ebf:/# apt-get update
Get:1 http://mirrors.aliyun.com/ubuntu focal InRelease [265 kB]
Get:2 http://mirrors.aliyun.com/ubuntu focal-updates InRelease [114 kB]
Get:3 http://mirrors.aliyun.com/ubuntu focal-backports InRelease [108 kB]
Get:4 http://mirrors.aliyun.com/ubuntu focal-security InRelease [114 kB]
Get:5 http://mirrors.aliyun.com/ubuntu focal/multiverse amd64 Packages [177 kB]
Get:6 http://mirrors.aliyun.com/ubuntu focal/restricted amd64 Packages [33.4 kB]
Get:7 http://mirrors.aliyun.com/ubuntu focal/universe amd64 Packages [11.3 MB]
Get:8 http://mirrors.aliyun.com/ubuntu focal/main amd64 Packages [1275 kB]
Get:9 http://mirrors.aliyun.com/ubuntu focal-updates/universe amd64 Packages [1421 kB]
Get:10 http://mirrors.aliyun.com/ubuntu focal-updates/restricted amd64 Packages [3092 kB]
Get:11 http://mirrors.aliyun.com/ubuntu focal-updates/multiverse amd64 Packages [32.0 kB]
Get:12 http://mirrors.aliyun.com/ubuntu focal-updates/main amd64 Packages [3633 kB]
Get:13 http://mirrors.aliyun.com/ubuntu focal-backports/main amd64 Packages [55.2 kB]
Get:14 http://mirrors.aliyun.com/ubuntu focal-backports/universe amd64 Packages [28.6 kB]
Get:15 http://mirrors.aliyun.com/ubuntu focal-security/universe amd64 Packages [1117 kB]
Get:16 http://mirrors.aliyun.com/ubuntu focal-security/restricted amd64 Packages [2942 kB]
Get:17 http://mirrors.aliyun.com/ubuntu focal-security/main amd64 Packages [3145 kB]
Get:18 http://mirrors.aliyun.com/ubuntu focal-security/multiverse amd64 Packages [29.3 kB]
Fetched 28.9 MB in 3s (8636 kB/s)
Reading package lists... Done
3. Install docker
apt-get install docker.io
A lot of programs of more than 400M need to be installed.
4. Start the docker service
Because the systemctl program no longer works in the docker container, the system will not automatically start the docker service after installing docker. You need to manually add the service startup script:
apt-get install vim
vi /etc/init.d/docker
Create a new /etc/init.d/docker file with the following contents:
#!/bin/sh
set -e
### BEGIN INIT INFO
# Provides: docker
# Required-Start: $syslog $remote_fs
# Required-Stop: $syslog $remote_fs
# Should-Start: cgroupfs-mount cgroup-lite
# Should-Stop: cgroupfs-mount cgroup-lite
# Default-Start: 2 3 4 5
# Default-Stop: 0 1 6
# Short-Description: Create lightweight, portable, self-sufficient containers.
# Description:
# Docker is an open-source project to easily create lightweight, portable,
# self-sufficient containers from any application. The same container that a
# developer builds and tests on a laptop can run at scale, in production, on
# VMs, bare metal, OpenStack clusters, public clouds and more.
### END INIT INFO
export PATH=/sbin:/bin:/usr/sbin:/usr/bin:/usr/local/sbin:/usr/local/bin
BASE=docker
# modify these in /etc/default/$BASE (/etc/default/docker)
DOCKERD=/usr/bin/dockerd
# This is the pid file managed by docker itself
DOCKER_PIDFILE=/var/run/$BASE.pid
# This is the pid file created/managed by start-stop-daemon
DOCKER_SSD_PIDFILE=/var/run/$BASE-ssd.pid
DOCKER_LOGFILE=/var/log/$BASE.log
DOCKER_OPTS=
DOCKER_DESC="Docker"
# Get lsb functions
. /lib/lsb/init-functions
if [ -f /etc/default/$BASE ]; then
. /etc/default/$BASE
fi
# Check docker is present
if [ ! -x $DOCKERD ]; then
log_failure_msg "$DOCKERD not present or not executable"
exit 1
fi
fail_unless_root() {
if [ "$(id -u)" != '0' ]; then
log_failure_msg "$DOCKER_DESC must be run as root"
exit 1
fi
}
case "$1" in
start)
fail_unless_root
touch "$DOCKER_LOGFILE"
chgrp docker "$DOCKER_LOGFILE"
ulimit -n 1048576
# Having non-zero limits causes performance problems due to accounting overhead
# in the kernel. We recommend using cgroups to do container-local accounting.
if [ "$BASH" ]; then
ulimit -u unlimited
else
ulimit -p unlimited
fi
log_begin_msg "Starting $DOCKER_DESC: $BASE"
start-stop-daemon --start --background \
--no-close \
--exec "$DOCKERD" \
--pidfile "$DOCKER_SSD_PIDFILE" \
--make-pidfile \
-- \
-p "$DOCKER_PIDFILE" \
$DOCKER_OPTS \
>> "$DOCKER_LOGFILE" 2>&1
log_end_msg $?
;;
stop)
fail_unless_root
if [ -f "$DOCKER_SSD_PIDFILE" ]; then
log_begin_msg "Stopping $DOCKER_DESC: $BASE"
start-stop-daemon --stop --pidfile "$DOCKER_SSD_PIDFILE" --retry 10
log_end_msg $?
else
log_warning_msg "Docker already stopped - file $DOCKER_SSD_PIDFILE not found."
fi
;;
restart)
fail_unless_root
docker_pid=$(cat "$DOCKER_SSD_PIDFILE" 2> /dev/null || true)
[ -n "$docker_pid" ] \
&& ps -p $docker_pid > /dev/null 2>&1 \
&& $0 stop
$0 start
;;
force-reload)
fail_unless_root
$0 restart
;;
status)
status_of_proc -p "$DOCKER_SSD_PIDFILE" "$DOCKERD" "$DOCKER_DESC"
;;
*)
echo "Usage: service docker {start|stop|restart|status}"
exit 1
;;
esac
Then add executable permissions:
chmod +x /etc/init.d/docker
Then you can start the docker service:
root@350983744ebf:/# service docker start
* Starting Docker: docker [ OK ]
root@350983744ebf:/# service docker status
* Docker is running
root@350983744ebf:/# docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
5. Verify whether docker can work properly
Let's start an Ubuntu container in the container:
root@350983744ebf:/# docker run -itd --name ubuntu --privileged --cap-add=NET_ADMIN ubuntu:20.04
Unable to find image 'ubuntu:20.04' locally
20.04: Pulling from library/ubuntu
96d54c3075c9: Pull complete
Digest: sha256:ed4a42283d9943135ed87d4ee34e542f7f5ad9ecf2f244870e23122f703f91c2
Status: Downloaded newer image for ubuntu:20.04
53ec4adbb55196fad5b31cdbf81ec9fe1e8229bb2df7be47b220911cc8bd0a7d
root@350983744ebf:/# docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
53ec4adbb551 ubuntu:20.04 "/bin/bash" 8 seconds ago Up 6 seconds ubuntu
This realizes the nesting doll of containers!