Docker

Install Docker Official

Uninstall old versions:

for pkg in docker.io docker-doc docker-compose docker-compose-v2 podman-docker containerd runc; do sudo apt-get remove $pkg; done

Install from apt repo:

# Add Docker's official GPG key:
sudo apt-get update
sudo apt-get install ca-certificates curl gnupg
sudo install -m 0755 -d /etc/apt/keyrings
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo gpg --dearmor -o /etc/apt/keyrings/docker.gpg
sudo chmod a+r /etc/apt/keyrings/docker.gpg

# Add the repository to Apt sources:
echo \
  "deb [arch="$(dpkg --print-architecture)" signed-by=/etc/apt/keyrings/docker.gpg] https://download.docker.com/linux/ubuntu \
  "$(. /etc/os-release && echo "$VERSION_CODENAME")" stable" | \
  sudo tee /etc/apt/sources.list.d/docker.list > /dev/null
sudo apt-get update

Install Docker Packages:

sudo apt-get install docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin

Setup Docker

Enable running docker commands without the use of sudo:

Check Groups for docker group:

cat /etc/group | grep docker

Add if not found:

sudo groupadd docker

Add user to docker group:

sudo usermod -aG docker $USER

Configure to start on boot with systemd:

sudo systemctl enable docker.service
sudo systemctl enable containerd.service

Docker Commands

Docker commands reference can be found here: docker command ref

Stop docker container

docker stop <container name>

remove container

docker rm <container name>

run container

docker run --name <container name>

Stop all the containers

docker stop $(docker ps -a -q)

Remove all the containers

docker rm $(docker ps -a -q)

Enter shell of container

docker exec -it <containerID> bash

Show images already pulled by docker and stored locally

docker images

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When running docker containers the run command will require extra options for containers with specific uses. Environment vairables can be added to a document container on startup using a .env file and the switch "--env-file=<path to env file>" in the run command

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Docker High CPU usage

See what containers are using system resources:

docker stats --all
docker stats --all --format "table {{.ID}}\t{{.Name}}\t{{.CPUPerc}}\t{{.MemUsage}}"

Check specific container for process:

docker ps | grep <container id>

Check the logs for high cpu use container:

docker logs --tail 100 <container Id>

Follow live logs:

docker logs --follow <container ID>

restart docker container:

docker restart <container name>

Template docker-compose file

Docs

Also see some other templates:awesome-compose github

Inspect Container by namespace

get process id of container:

CONTAINER_PID=$(pgrep <containername> | sort | head -n 1) #gets PID of container

sudo lsns -p ${CONTAINER_PID} #gets all namespaces for the process

Info about the namespaces:

• mnt (Mount) - the container has an isolated mount table.
• uts (UNIX Time-Sharing) - the container is able to have its own hostname and domain name.
• ipc (Interprocess Communication) - processes inside the container can communicate via system-level IPC only to processes inside the same container.
• pid (Process ID) - processes inside the container are only able to see other processes inside the same container or inside the same pid namespace.
• net (Network) - the container gets its own set of network devices, IP protocol stacks, port numbers, etc.
• cgroup (Cgroup) - the container has its own virtualized view of cgroups (not to be confused with cgroups themselves).

Copy Files into container

To copy files into/outof a running container use the docker cp command:

docker cp [OPTIONS] CONTAINER:SRC_PATH DEST_PATH|-
docker cp [OPTIONS] SRC_PATH|- CONTAINER:DEST_PATH

Export file system of container

CONT_ID=$(docker create nginx:latest) #get container id
docker export ${CONT_ID} -o nginx.tar.gz # export container to tarball

docker export $(docker create nginx:latest) | tar -xC <dest> # oneliner to extract to destinatin folder