Docker Commands
Docker underwent a syntax overhaul. Some old commands still work but it's important to remember that for a DCA exam we should always start using the new commands.
docker ps (old syntax)
docker container ls (new syntax)
docker info (old syntax)
docker system info (new syntax)
Everything on the exam regarding old syntax will be considered an error. These old commands are not considered aliases, they still work, but will be discontinued. So get used to the new ones.
Some things are actually aliases.
docker container ls
docker container list
Either of these two are in the new syntax, so for the exam either one is correct. Notice that the structure remains when it's an alias.
Auto Complete
To help with auto complete, it's good to have it installed. https://docs.docker.com/compose/completion/
For this, you need to have the bash-completion package installed, install it using your distro's package manager and then run the commands below.
For the docker command
sudo curl -L curl https://raw.githubusercontent.com/docker/docker-ce/master/components/cli/contrib/completion/bash/docker -o /etc/bash_completion.d/docker.sh
For the docker-compose command that we'll see later
sudo curl -L https://raw.githubusercontent.com/docker/compose/master/contrib/completion/bash/docker-compose -o /etc/bash_completion.d/docker-compose
--Help
For Docker help, it offers a very explanatory help.
❯ docker --help
Usage: docker [OPTIONS] COMMAND
A self-sufficient runtime for containers
Options:
--config string Location of client config files (default "/home/david/.docker")
-c, --context string Name of the context to use to connect to the daemon (overrides DOCKER_HOST env var and default context set with "docker context use")
-D, --debug Enable debug mode
-H, --host list Daemon socket(s) to connect to
-l, --log-level string Set the logging level ("debug"|"info"|"warn"|"error"|"fatal") (default "info")
--tls Use TLS; implied by --tlsverify
--tlscacert string Trust certs signed only by this CA (default "/home/david/.docker/ca.pem")
--tlscert string Path to TLS certificate file (default "/home/david/.docker/cert.pem")
--tlskey string Path to TLS key file (default "/home/david/.docker/key.pem")
--tlsverify Use TLS and verify the remote
-v, --version Print version information and quit
Management Commands:
builder Manage builds
buildx* Docker Buildx (Docker Inc., v0.8.2-docker)
compose* Docker Compose (Docker Inc., 2.6.0)
config Manage Docker configs
container Manage containers
context Manage contexts
image Manage images
manifest Manage Docker image manifests and manifest lists
network Manage networks
node Manage Swarm nodes
plugin Manage plugins
secret Manage Docker secrets
service Manage services
stack Manage Docker stacks
swarm Manage Swarm
system Manage Docker
trust Manage trust on Docker images
volume Manage volumes
Commands:
attach Attach local standard input, output, and error streams to a running container
build Build an image from a Dockerfile
commit Create a new image from a container's changes
cp Copy files/folders between a container and the local filesystem
create Create a new container
diff Inspect changes to files or directories on a container's filesystem
events Get real time events from the server
exec Run a command in a running container
export Export a container's filesystem as a tar archive
history Show the history of an image
images List images
import Import the contents from a tarball to create a filesystem image
info Display system-wide information
inspect Return low-level information on Docker objects
kill Kill one or more running containers
load Load an image from a tar archive or STDIN
login Log in to a Docker registry
logout Log out from a Docker registry
logs Fetch the logs of a container
pause Pause all processes within one or more containers
port List port mappings or a specific mapping for the container
ps List containers
pull Pull an image or a repository from a registry
push Push an image or a repository to a registry
rename Rename a container
restart Restart one or more containers
rm Remove one or more containers
rmi Remove one or more images
run Run a command in a new container
save Save one or more images to a tar archive (streamed to STDOUT by default)
search Search the Docker Hub for images
start Start one or more stopped containers
stats Display a live stream of container(s) resource usage statistics
stop Stop one or more running containers
tag Create a tag TARGET_IMAGE that refers to SOURCE_IMAGE
top Display the running processes of a container
unpause Unpause all processes within one or more containers
update Update configuration of one or more containers
version Show the Docker version information
wait Block until one or more containers stop, then print their exit codes
Run 'docker COMMAND --help' for more information on a command.
To get more help with docker, check out our guides at https://docs.docker.com/go/guides/
Main Commands
docker system: brings system results docker container works with containers docker image manipulates images docker volume works with volumes docker network works with the network
main commands have secondary commands, many are the same in fact
Let's run this command to run a hello world container from docker.
vagrant@master:~$ docker container run hello-world
Hello from Docker!
This message shows that your installation appears to be working correctly.
To generate this message, Docker took the following steps:
1. The Docker client contacted the Docker daemon.
2. The Docker daemon pulled the "hello-world" image from the Docker Hub.
(amd64)
3. The Docker daemon created a new container from that image which runs the
executable that produces the output you are currently reading.
4. The Docker daemon streamed that output to the Docker client, which sent it
to your terminal.
To try something more ambitious, you can run an Ubuntu container with:
$ docker run -it ubuntu bash
Share images, automate workflows, and more with a free Docker ID:
https://hub.docker.com/
For more examples and ideas, visit:
https://docs.docker.com/get-started/
What did it do? Downloaded an image, ran the image and died. Now, we already have an image, a dead container, let's test.
ls or list
lists what is actually being used at the moment
vagrant@master:~$ docker container ls
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
vagrant@master:~$ docker images ls
REPOSITORY TAG IMAGE ID CREATED SIZE
vagrant@master:~$ docker volume ls
DRIVER VOLUME NAME
vagrant@master:~$ docker network ls
NETWORK ID NAME DRIVER SCOPE
487679e6deca bridge bridge local
d1a3aee195f4 host host local
fd926f9c1bbe none null local
vagrant@master:~$
Note that it didn't list the container or the hello-world image, because it has already died.
If we want to see everything we use --all
vagrant@master:~$ docker images --all
REPOSITORY TAG IMAGE ID CREATED SIZE
hello-world latest feb5d9fea6a5 8 months ago 13.3kB
vagrant@master:~$ docker container list --all
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
6fc6ee0898d7 hello-world "/hello" 3 minutes ago Exited (0) 3 minutes ago charming_aryabhata
# to see only the resource ids
vagrant@master:~$ docker container list --all -q
6fc6ee0898d7
vagrant@master:~$ docker images -q
feb5d9fea6a5
vagrant@master:~$ docker network ls -q
487679e6deca
d1a3aee195f4
fd926f9c1bbe
vagrant@master:~$ docker volume ls -q
Search
https://docs.docker.com/engine/reference/commandline/search/
used to search for plugins and images in the registry. Avoid using unofficial images for your security.
In the command below I applied a filter in the search to list only the official ones
vagrant@master:~$ docker search --filter is-official=true debian
NAME DESCRIPTION STARS OFFICIAL AUTOMATED
ubuntu Ubuntu is a Debian-based Linux operating sys… 14456 [OK]
debian Debian is a Linux distribution that's compos… 4341 [OK]
neurodebian NeuroDebian provides neuroscience research s… 91 [OK]
vagrant@master:~$
Now I added one more filter to get only those with stars above 5000 and only the official one came.
vagrant@master:~$ docker search --filter is-official=true --filter stars=5000 debian
NAME DESCRIPTION STARS OFFICIAL AUTOMATED
ubuntu Ubuntu is a Debian-based Linux operating sys… 14456 [OK]
Pull
Used to download the image we want from the registry. Taking advantage of the filter above we know we're going to download ubuntu.
These images are stored on dockerhub which is docker's official registry.
vagrant@master:~$ docker image pull ubuntu
Using default tag: latest
latest: Pulling from library/ubuntu
405f018f9d1d: Pull complete
Digest: sha256:b6b83d3c331794420340093eb706a6f152d9c1fa51b262d9bf34594887c2c7ac
Status: Downloaded newer image for ubuntu:latest
docker.io/library/ubuntu:latest
vagrant@master:~$ docker image ls
REPOSITORY TAG IMAGE ID CREATED SIZE
ubuntu latest 27941809078c 13 days ago 77.8MB
hello-world latest feb5d9fea6a5 8 months ago 13.3kB
run, attach, start
Let's run the debian image (last parameter), which we don't have in our pull. Docker looks for the image with the name passed locally, if it doesn't find it, it tries to pull automatically from the registries we have, in this case only dockerhub by default.
-d (detach) -i (interactive) -t (tty) = -dit
-name we pass a name to identify the container, if we hadn't passed it, it would give a random name, see in the table under NAMES
-hostname we pass a hostname for it to already place in /etc/hostname inside the container.
vagrant@master:~$ docker container run -dit --name debiandca --hostname mydebian.local debian
Unable to find image 'debian:latest' locally
latest: Pulling from library/debian
e756f3fdd6a3: Pull complete
Digest: sha256:3f1d6c17773a45c97bd8f158d665c9709d7b29ed7917ac934086ad96f92e4510
Status: Downloaded newer image for debian:latest
30755da9310e0b921213f457b7bb6dac877443e00b775dbe4e55d7b91b0edb72
vagrant@master:~$ docker container ls
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
30755da9310e debian "bash" 7 seconds ago Up 5 seconds debiandca
What keeps this container alive is bash which is the command that keeps it alive. If we run something on this bash that gives an exit code different from zero, the container will die.
Let's check /etc/hostname and see what happens if we list the container again, let's attach to the container for that.
vagrant@master:~$ docker container attach debiandca
root@mydebian:/# cat /etc/host
host.conf hostname hosts
root@mydebian:/# cat /etc/hostname
mydebian.local
root@mydebian:/# exit
vagrant@master:~$ docker container ls -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
30755da9310e debian "bash" 24 minutes ago Exited (0) 5 seconds ago debiandca
6fc6ee0898d7 hello-world "/hello" 51 minutes ago Exited (0) 51 minutes ago charming_aryabhata
Notice that the container disappeared, because the exit gave a non-zero exit code.
To start the container again...
vagrant@master:~$ docker container start debiandca
debiandca
To exit the container without killing it there is a key sequence called Read Escape Sequence which is CTRL + P + Q. Let's attach to it and exit with the Read Escape Sequence and check.
vagrant@master:~$ docker container ls
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
30755da9310e debian "bash" 31 minutes ago Up 5 minutes debiandca
vagrant@master:~$ docker attach debiandca
root@mydebian:/# read escape sequence
vagrant@master:~$ docker container ls
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
30755da9310e debian "bash" 31 minutes ago Up 6 minutes debiandca
Still alive.
logs
will bring the logs from the standard output of the container. In this case I ran some small commands for testing.
vagrant@master:~$ docker container logs debiandca
root@mydebian:/# exit
exit
root@mydebian:/# cat /etc/hosts
127.0.0.1 localhost
::1 localhost ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
172.17.0.2 mydebian.local mydebian
vagrant@master:~$
stop and rm
To stop a container we use stop. Let's check what we have running, stop the container, check again to see that there's nothing, but with the list --all command we can see it still exists, but it's not running. Then we'll actually remove it and check again.
vagrant@master:~$ docker container ls
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
30755da9310e debian "bash" 45 minutes ago Up 20 minutes debiandca
vagrant@master:~$ docker container stop debiandca
debiandca
vagrant@master:~$ docker container ls
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
vagrant@master:~$ docker container list --all
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
30755da9310e debian "bash" 46 minutes ago Exited (137) 18 seconds ago debiandca
6fc6ee0898d7 hello-world "/hello" About an hour ago Exited (0) About an hour ago charming_aryabhata
vagrant@master:~$ docker container rm debiandca
debiandca
vagrant@master:~$ docker container list --all
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
6fc6ee0898d7 hello-world "/hello" About an hour ago Exited (0) About an hour ago charming_aryabhata
vagrant@master:~$
Does removing a container remove the image? No.
Let's check and see that the image is still there. If we run another container with the same image, it won't need to pull the image.
vagrant@master:~$ docker image ls --all
REPOSITORY TAG IMAGE ID CREATED SIZE
ubuntu latest 27941809078c 13 days ago 77.8MB
debian latest 4eacea30377a 3 weeks ago 124MB
hello-world latest feb5d9fea6a5 8 months ago 13.3kB
vagrant@master:~$
If we want to remove a container that is running, what will happen? We'll get an error. For that we use -f to force.
vagrant@master:~$ docker container run -dit --name debiandca --hostname mydebian.local debian
63c49ea76047c2f7d852926a6f6f6dfea051b8717f910989736dd3e1d3068614
vagrant@master:~$ docker container ls
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
63c49ea76047 debian "bash" 19 seconds ago Up 19 seconds debiandca
vagrant@master:~$ docker container rm debiandca
Error response from daemon: You cannot remove a running container 63c49ea76047c2f7d852926a6f6f6dfea051b8717f910989736dd3e1d3068614. Stop the container before attempting removal or force remove
vagrant@master:~$ docker container rm -f debiandca
debiandca
vagrant@master:~$ docker container ls
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
The rm command is used to remove, whether an image, a network, a container, a volume...
rm removes a list, so we can pass a complete one for it to remove everything if we want.
docker image rm -f $(docker image ls -q)
to remove all containers
docker container rm -f $(docker container ls -aq)
vagrant@master:~$ docker image ls
REPOSITORY TAG IMAGE ID CREATED SIZE
ubuntu latest 27941809078c 13 days ago 77.8MB
debian latest 4eacea30377a 3 weeks ago 124MB
hello-world latest feb5d9fea6a5 8 months ago 13.3kB
vagrant@master:~$ docker image rm -f $(docker image ls -q)
Untagged: ubuntu:latest
Untagged: ubuntu@sha256:b6b83d3c331794420340093eb706a6f152d9c1fa51b262d9bf34594887c2c7ac
Deleted: sha256:27941809078cc9b2802deb2b0bb6feed6c236cde01e487f200e24653533701ee
Deleted: sha256:a790f937a6aea2600982de54a5fb995c681dd74f26968d6b74286e06839e4fb3
Untagged: debian:latest
Untagged: debian@sha256:3f1d6c17773a45c97bd8f158d665c9709d7b29ed7917ac934086ad96f92e4510
Deleted: sha256:4eacea30377a698ef8fbec99b6caf01cb150151cbedc8e0b1c3d22f134206f1a
Deleted: sha256:e7597c345c2eb11bce09b055d7c167c526077d7c65f69a7f3c6150ffe3f557ea
Untagged: hello-world:latest
Untagged: hello-world@sha256:13e367d31ae85359f42d637adf6da428f76d75dc9afeb3c21faea0d976f5c651
Deleted: sha256:feb5d9fea6a5e9606aa995e879d862b825965ba48de054caab5ef356dc6b3412
Deleted: sha256:e07ee1baac5fae6a26f30cabfe54a36d3402f96afda318fe0a96cec4ca393359
vagrant@master:~$ docker image ls
REPOSITORY TAG IMAGE ID CREATED SIZE
vagrant@master:~$
cp and exec
cp is the copy command. It works as if we were copying via ssh something into the container.
Let's create a file and transfer it into the container, then let's execute a command without needing to attach to the container and check the file.
vagrant@master:~$ docker container run -dit --name debiandca --hostname mydebian.local debian
Unable to find image 'debian:latest' locally
latest: Pulling from library/debian
e756f3fdd6a3: Pull complete
Digest: sha256:3f1d6c17773a45c97bd8f158d665c9709d7b29ed7917ac934086ad96f92e4510
Status: Downloaded newer image for debian:latest
a0a45037b974b67619c7b758c6fabe7c87a7111720b47bcf477a269293dda27b
vagrant@master:~$ echo "tribulus terrestris tetris" > /tmp/arquivo
vagrant@master:~$ cat /tmp/arquivo
tribulus terrestris tetris
vagrant@master:~$ docker container cp /tmp/arquivo debiandca:/tmp/arquivo
vagrant@master:~$ docker container exec debiandca cat /tmp/arquivo
tribulus terrestris tetris
vagrant@master:~$