I've used Docker on Windows and macOS for the past couple years. Often, when things got really messed up, I found it faster to use the Reset to factory defaults option in the Docker GUI to do a clean reset than to troubleshoot whatever problem was giving me grief.
Now I'm using Ubuntu 20.04 and I can't find this option. I found a long list of commands to remove/reset individual components but where is the single command for this like Windows/macOS?
Use your OS's package manager to uninstall the Docker package; then
sudo rm -rf /var/lib/docker
That should completely undo all Docker-related things.
Note that the "Desktop" applications have many more settings (VM disk/memory size, embedded Kubernetes, ...). The native-Linux Docker installations tend to have very few, and generally the only way to set them is by directly editing the JSON configuration file in /etc. So "reset Docker" doesn't really tend to be an issue on native Linux.
As always, make sure you have an external copy of your images (in Docker Hub or a registry like ECR) or you can rebuild them from Dockerfiles, your containers are designed to tolerate being deleted and recreated, and if you use named volumes, you have backups of those.
You can use this command:
docker system prune -a
Description:
WARNING! This will remove:
- all stopped containers
- all networks not used by at least one container
- all images without at least one container associated to them
- all build cache
Related
I am a docker newbie. I just installed Docker and Docker Desktop as per offical instruction. Soon, I start to have problem like: the Docker Desktop does not show container. I think it's because I haven’t set the contexts same for with and without sudo privilege, according to this post.
But I don’t understand why I only have the “default” option for “sudo docker context ls”. Please help me on this. Many thanks!
OS:Ubuntu 20.04.5 LTS
screenshot
The docker context data is stored in the user's home directory. When you use sudo, that changes users and home directories. Without sudo it might look in /home/yourname/.docker/contexts, but when you switch to root with sudo it also changes home directories and looks in /root/.docker/contexts.
You do not need Docker Desktop on native Linux. Installing Docker (what the Docker documentation now calls "Docker Engine") through your OS's package manager is sufficient. If you are on a single-user system, you can grant your ordinary user access to the Docker socket, but be aware that it's all but trivial to use this access to root the entire host.
When you do uninstall Docker Desktop, there are additional files in your home directory you need to remove
rm -rf $HOME/.docker/desktop
$EDITOR $HOME/.docker/config.json
# and remove `credsStore` and `currentContext`
Once you've done this cleanup, you'll revert to Docker's default behavior of using the $DOCKER_SOCK environment variable, or without that, /var/run/docker.sock. That system-global Docker socket file is the same regardless of which user you are, and it won't be affected by sudo.
I have a library that I'd like to test on FreeBSD. My CI setup doesn't have any FreeBSD systems, and adding them would be difficult, but I can spin up a VM inside my CI script. (In fact, I already do this to test on more exotic Linux kernel versions.)
For Linux, this is pretty easy: grab a pre-built machine image from some distro site, and use cloud-init to inject a first-run script, done.
Is it possible to do the same thing with FreeBSD? I'm looking for an automated way to take a standard FreeBSD machine image (e.g. downloaded from https://freebsd.org), boot it, and inject a program to run. The tricky part is that it should be entirely automated – I don't want to have to manually click through an installer ever time FreeBSD makes a new release.
Out of the box, there is no option like cloud-init but you could create your own image and use firstboot for example, this script is used to bootstrap a VM with saltstack in AWS:
#!/bin/sh
# KEYWORD: firstboot
# PROVIDE: set_hostname
# REQUIRE: NETWORKING
# BEFORE: login
. /etc/rc.subr
name="set_hostname"
rcvar=set_hostname_enable
start_cmd="set_hostname_run"
stop_cmd=":"
export AWS_ACCESS_KEY_ID=key
export AWS_SECRET_ACCESS_KEY=secret
export AWS_DEFAULT_REGION=region
TAG_NAME="Salt"
INSTANCE_ID=$(/usr/local/bin/curl -s http://169.254.169.254/latest/meta-data/instance-id)
REGION=$(/usr/local/bin/curl -s http://169.254.169.254/latest/meta-data/placement/availability-zone | sed 's/.$//')
TAG_VALUE=$(/usr/local/bin/aws ec2 describe-tags --filters "Name=resource-id,Values=${INSTANCE_ID}" "Name=key,Values=$TAG_NAME" --region ${REGION} --output=text | cut -f5)
set_hostname_run()
{
hostname ${INSTANCE_ID}
sysrc hostname="${INSTANCE_ID}"
sysrc salt_minion_enable="YES"
echo ${INSTANCE_ID} > /usr/local/etc/salt/minion_id
pw usermod root -c "root on ${INSTANCE_ID}"
if [ ! -z "${TAG_VALUE}" ]; then
echo "node_type: ${TAG_VALUE}" > /usr/local/etc/salt/grains
fi
service salt_minion start
}
load_rc_config $name
run_rc_command "$1"
To create your own images you could use this script as a starting point: https://github.com/fabrik-red/images/blob/master/fabrik.sh#L124, more info here: https://fabrik.red/post/creating-the-image/
You can also simply install FreeBSD in Virtualbox, configure scripts related to firstboot, test and when you are happy with the results, export it, just be careful before exporting it that /firstboot exists (touch /firstboot) since after the first boot it will be removed and it could happen that after you export it if is not present it will not call the scripts.
After you have created the image you can use it multiple times, no need to create a new "custom" VM every time, it all depends on the scripts you use to bootstrap and load the scripts on the "firstboot".
I looked into this a bit more, and it turns out that it is possible, though it's quite awkward.
There are three kinds of official FreeBSD releases: pre-installed VMs, ISO installers, and USB stick installers.
The official pre-installed VM images don't offer any way to script them from outside by default. And they use the FreeBSD UFS filesystem, which isn't modifiable from any common OS. (Linux can mount UFS read-only, and has some code for read-write support, but the read-write support is disabled by default and requires a custom kernel.) So there's no easy way to programmatically modify them unless you already have a FreeBSD install.
The USB stick installers also use UFS filesystems, so that's out. So do the pre-built live CD's I found, like mfsBSD (the CD itself is iso9660, but it's just a container for a big UFS blob that gets unpacked into memory).
So that leaves the CD installers. It turns out that these actually use iso9660 for their actual file layout. And we don't need FreeBSD to work with iso9660!
So what you have to do is:
Download the CD installer
Modify the files on it to do the install without user interaction, apply some custom configuration to the new system, and then shut down
Use your favorite VM runner to boot up the CD with a blank hard drive image, and let it run to install FreeBSD onto that hard drive
Boot up the hard drive, and it will do whatever you want.
There are a ton of fiddly details that I'm glossing over, but that's the basic idea. There's also a fully-worked example here: https://github.com/python-trio/trio/pull/1509/
To "inject" your software you generally need to be able to write to the filesystem, and the most reliable way of doing that is to run the system itself. In other words, have a FreeBSD VM to create FreeBSD VMs - you can either build them locally (man 7 release), or fetch VM images from http://download.FreeBSD.org, mount their rootfs somewhere, put your software wherever you need it, and make it execute it from mounted filesystem's /etc/rc.local.
I'm quite new at docker, but I'm facing a problem I have no idea how to solve it.
I have a jenkins (docker) image running and everything was fine. A few days ago I created a job so I can run my nodejs tests every time a pull request is made. one of the job's build steps is to run npm install. And the job is constantly failing with this error:
tar (child): bzip2: Cannot exec: No such file or directory
So, I know that I have to install bzip2 inside the jenkins container, but how do I do that? I've already tried to run docker run jenkins bash -c "sudo apt-get bzip2" but I got: bash: sudo: command not found.
With that said, how can I do that?
Thanks in advance.
Answer to this lies inside the philosophy of dcoker containers. Docker containers are/should be immutable. So, this is what you can try to fix this issue.
Treat your base image i.e, jenkins as starting point.
login to this base image and install bzip2.
commit these changes and this should result in a new image.
Now use above image from step 3 to install any other package like npm.
Now commit above image.
Note: To execute commands in much controlled way, I always prefer to use something like this;
docker exec -it jenkins bash
In nutshell, answer to both of your current issues lie in the fact that images are immutable so to make any change that will get propagated is to commit them and use newly created image to make further changes. I hope this helps.
Lots of issues here, but the biggest one is that you need to build your images with the tools you need rather than installing inside of a running container. As techtrainer mentions, images are immutable and don't change (at least from your running container), and containers are disposable (so any changes you make inside them are lost when you restart them unless your data is stored outside the container in a volume).
I do disagree with techtrainer on making your changes in a container and committing them to an image with docker commit. This will work, but it's the hand built method that is very error prone and not easily reproduced. Instead, you should leverage a Dockerfile and use docker build. You can either modify the jenkins image you're using by directly modifying it's Dockerfile, or you can create a child image that is FROM jenkins:latest.
When modifying this image, the Jenkins image is configured to run as the user "jenkins", so you'll need to switch to root to perform your application installs. The "sudo" app is not included in most images, but external to the container, you can run docker commands as any user. From the cli, that's as easy as docker run -u root .... And inside your Dockerfile, you just need a USER root at the top and then USER jenkins at the end.
One last piece of advice is to not run your builds directly on the jenkins container, but rather run agents with your needed build tools that you can upgrade independently from the jenkins container. It's much more flexible, allows you to have multiple environments with only the tools needed for that environment, and if you scale this up, you can use a plugin to spin up agents on demand so you could have hundreds of possible agents to use and only be running a handful of them concurrently.
EDIT +2=Just fyi, i am a root user which means i do not have type out superuser do (sudo) every time i do a authorized only cmd.
Alright so after about 24 hours of researching Docker i am a little upset if i got my facts straight.
As a quick recap, docker serves as a way to write code or configuration file changes for a specific web service, run environment, virtual machines, all from the cozy confines of a linux terminal/text file. This is beyond a doubt an amazing feature: to have code or builds you made on one computer work on an unlimited number of other machines is truly a breakthrough. While i am annoyed that the terminology is wrong with respect to whats containers and what are images (images are save points of layers of code that are made from dockers servers or can be created from containers which require a base image to go off of. Dockerfiles serve as a way to automate the build process of making images by running all the desired layers and roll them into one image so it can be accessed easily.).
See the catch is with docker is that "sure it can be deployed on a variety of different operating systems and use their respective commands". But those commands do not really come to pass on say something like the local environment though. While running some tests on a dockerbuild working with centos, the basic command structure goes
FROM centos
RUN yum search epel
RUN yum install -y epel-release.noarch
RUN echo epel installed!
So this works within the docker build and says it succesfully installs it.
The same can be said with ubuntu by running an apt-cache instead of yum. But going back to the centos VM, it DOES NOT state that epel has been installed because when attempting to run the command of
yum remove epel-release.noarch
it says "no packages were to be removed yet there is a package named ...". So then, if docker is able to be multi-platform why can it not actually create those changes on the local platform/image we are targeting? The docker builds run a simulation of what is going to happen on that particular environment but i can not seem to make it come to pass. This just defeats one of my intended purposes of the docker if it can not change anything local to the system one is using, unless i am missing something.
Please let me know if anyone has a solution to this dilemma.
EDIT +1=Ok so i figured out yesterday what i was trying to do was to view and modify the container which can be done by doing either docker logs containerID or docker run -t -i img /bin/sh which would put me into an interactive shell to make container changes there. Still, i want to know if theres a way to make docker comunicate to the local environment from within a container.
So, I think you may have largely missed the point behind Docker, which is the management of containers that are intentionally isolated from your local environment. The idea is that you create containerized applications that can be run on any Docker host without needing to worry about the particular OS installed or configuration of the host machine.
That said, there are a variety of ways to break this isolation if that's really what you want to do.
You can start a container with --net=host (and probably --privileged) if you want to be able to modify the host network configuration (including interface addresses, routing tables, iptables rules, etc).
You can parts of (or all of) the host filesystem as volumes inside the container using the -v command line option. For example, docker run -v /:/host ... would expose the root of your host filesystem as /host inside the container.
Normally, Docker containers have their own PID namespace, which means that processes on the host are not visible inside the container. You can run a container in the host PID namespace by using --pid=host.
You can combine these various options to provide as much or as little access to the host as you need to accomplish your particular task.
If all you're trying to do is install packages on the host, a container is probably the wrong tool for the job.
I am reading a lot of Docker guides where the will often use some Ubuntu base image and in the Dockerfile directly or in a bash script that gets copy to container and run on start, it has things like 'apt-get upgrade'
As i understand it, the container still uses the hosts kernel. So what happens when the apt-get upgrade includes a kernel upgrade? Does it create a /boot and install the files as usual but the underlying LXC has some pass-through/whitelist mechanism for specific directories that always come from host... so it ignores those files in guest container ?
Thanks
fLo
The host's /boot is not visible to a Docker container, and the kernel image package should not be installed in such a container, since it's not needed. (Even if it is, though, it's entirely inert.)