Usage#

    diyc [hv][-m NUMBER] [-ip IPV4 ADDRESS] <NAME> <IMAGE> <CMD>

    -h, --help           print the help

    -i, --ip             ip address of the container, if not set then host
                         network is used. It must be in the 172.16.0/16 network
                         as the bridge diyc0 is 172.16.0.1

    -m, --mem            maximum size of the memory in MB allowed for the container
                         by default there no explicit limit defined.

    -v, --verbose        more verbose output

    <NAME>               name of the container, needs to be unique

    <IMAGE>              image to be used for the container, must be a directory name
                         under the images directory

    <CMD>                command to be executed inside the container

Example: Get a container running#

This is an example session showing how to get a container with minimal debian based system up and running from zero.

$ git clone [email protected]:w-vi/diyc.git
Cloning into 'diyc'...
remote: Counting objects: 9, done.
remote: Compressing objects: 100% (8/8), done.
remote: Total 9 (delta 1), reused 9 (delta 1), pack-reused 0
Receiving objects: 100% (9/9), 12.95 KiB | 0 bytes/s, done.
Resolving deltas: 100% (1/1), done.

$ cd diyc

$ make setup
sudo iptables -A FORWARD -i enp5s0 -o veth -j ACCEPT || true
sudo iptables -A FORWARD -o enp5s0 -i veth -j ACCEPT || true
sudo iptables -t nat -A POSTROUTING -s 172.16.0.0/16 -j MASQUERADE || true
sudo ip link add name diyc0 type bridge || true
sudo ip addr add dev diyc0 172.16.0.1/24 || true
sudo ip link set diyc0 up || true
sudo iptables -A FORWARD -i enp5s0 -o diyc0 -j ACCEPT || true
sudo iptables -A FORWARD -o enp5s0 -i diyc0 -j ACCEPT || true
sudo iptables -A FORWARD -o diyc0 -i diyc0 -j ACCEPT || true
mkdir -p containers
mkdir -p images

$ make
gcc -std=c99 -Wall -Werror -O2 src/diyc.c -o diyc
gcc -std=c99 -Wall -Werror -O2 src/nsexec.c -o nsexec

$ docker pull debian
Using default tag: latest
latest: Pulling from library/debian
Digest: sha256:72f784399fd2719b4cb4e16ef8e369a39dc67f53d978cd3e2e7bf4e502c7b793
Status: Image is up to date for debian:latest

$ docker run -ti debian /bin/bash

$ docker ps
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES
2c924241399c        debian              "/bin/bash"         21 seconds ago      Up 20 seconds                           epic_leavitt

$ docker export 2c924241399c >! debian.tar

$ mkdir images/debian

$ tar -xf debian.tar -C images/debian/

$ sudo ./diyc my1 debian bash

  [email protected]:/> exit
  exit

Example: Network between two containers#

Spin up two different containers with different IPs. In this case it they are based on debian so Python and curl need to be installed first.

$ sudo ./diyc -i 172.16.0.30 server debian bash
[email protected]:/> apt-get update && apt-get install python
[email protected]:/> python -m SimpleHTTPServer
Serving HTTP on 0.0.0.0 port 8000 ...

$ sudo ./diyc -i 172.16.0.31 client debian bash
[email protected]:/> apt-get update && apt-get install curl
[email protected]:/> curl http://172.16.0.30:8000

# it is accessible from the host too
$ curl http://172.16.0.30:8000

Example: Limit memory used by cgroups#

Having an image with python or perl installed you can easily see the OOM killer in action. We will allow only 10 MB of memory.

$ sudo ./diyc -m 10 cgroup debian bash
[email protected]:/> python -c 'str = " " * 100000'
[email protected]:/> python -c 'str = " " * 1000000'
[email protected]:/> python -c 'str = " " * 10000000'
Killed

Removing exited containers#

Because containers after exit leave their filesystem behind and it is not destroyed you can run it again. The data are stored in the containers/<name>/ directory so as long as this directory exists you can start and stop the container. To remove it just sudo rm -rf containers/<name>.

Removing the diyc0 bridge and iptables rules#

Just run make net-clean.