I am new to docker and this is just a fascinating tool. However, I can't understand one thing about it. Simple Dockerfile usually begins with OS name and version, like:
FROM ubuntu:xenial
....
But which Linux OS will be used for Dockerfile like
FROM perl
....
or
FROM python:3.6
....
Of course I can find this out by running a container from this image and printing out the OS info, like:
docker run -it --rm perl bash
# cat /etc/*-release
or
docker run -it --rm python:3.6 bash
# cat /etc/*-release
BTW, In both cases the OS is "Debian GNU/Linux 10 (buster)".
So, my questions are:
How do I find out which OS will be run for a specific docker image without actually creating a docker container from it (the docker inspect command does not provide this info: docker inspect perl | grep -i Debian)
How do I change the OS type for existing docker image. For example, I have an image that uses Ubuntu 14.04, and I want to change it to Ubuntu 18.04..
Thank you for your help:)
A docker image doesn't need an OS. There's a possibility of extending the scratch image which is purposely empty and the container may only contain one binary or some volume.
Having an entire OS is possible but also misleading: The host shares its kernel with the container. (This is not a virtual machine.)
That means that no matter what "OS" you are running, the same kernel in the container is found:
Both:
docker run --rm -it python:3.6 uname -a
docker run --rm -it python:3.6-alpine uname -a
will report the same kernel of your host machine.
So you have to look into different ways:
docker run --rm -it python:3.6 cat /etc/os-release
or
lsb_release -sirc
or for Cent OS:
cat /etc/issue
In stead of scratch, a lot of images are also alpine-based to avoid the size overhead. An ubuntu base image can easily have 500MB fingerprint whereas alpine uses around 5MB; so I rather check for that as well.
Also avoid the trap of manually installing everything onto one Ubuntu image inside one big Dockerfile. Docker works best if each service is its own container that you link together. (For that check out docker-compose.)
In the end, you as an user shouldn't care about the OS of an image, but rather its size. Only as a developer of the Dockerfile is it relevant to know the OS and that you'll find out either by looking into the Dockerfile the image was built (if it's on docker hub you can read it there).
You basically have to look what was used to create your image an use the appropriate tools for the job. (Debian-based images use apt-get, alpine uses apk, and Fedora uses yum.)
How do I find out which OS will be run for a specific docker image without actually creating a docker container from it
The only way to determine what os is being used is as you have described: spawn a container and print the os information. There is no metadata that says "this image was build using <x>".
In many (but not all) situations, this information may not be especially important.
How do I change the OS type for existing docker image. For example, I have an image that uses Ubuntu 14.04, and I want to change it to Ubuntu 18.04..
If you have access to the Dockerfile used to build the image, you can of course change the base image (the image named in the FROM line) and build a new one, but you may find that this requires a number of other changes due to different software versions in your updated image.
You can use "docker cp" to extract the "/etc/os-release" file without starting the container:
$ docker pull ubuntu:latest
Status: Image is up to date for ubuntu:latest
$ docker create ubuntu:latest
2e5da8bf02312870acd0436e0cc4eb28fbcc998f766cd9639c37101f65739553
$ docker cp -L 2e5da8bf02312870acd0436e0cc4eb28fbcc998f766cd9639c37101f65739553:/etc/os-release .
$ docker rm 2e5da8bf02312870acd0436e0cc4eb28fbcc998f766cd9639c37101f65739553
$ cat ./os-release
NAME="Ubuntu"
VERSION="20.04.2 LTS (Focal Fossa)"
ID=ubuntu
ID_LIKE=debian
PRETTY_NAME="Ubuntu 20.04.2 LTS"
VERSION_ID="20.04"
HOME_URL="https://www.ubuntu.com/"
SUPPORT_URL="https://help.ubuntu.com/"
BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/"
PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy"
VERSION_CODENAME=focal
UBUNTU_CODENAME=focal
Note: I had to use "docker cp -L" because /etc/os-release is a symlink on ubuntu:latest.
Honestly, I find this to be a lot of trouble just to avoid starting the container, and it requires the "/etc/os-release" file to be present. If you're willing to (very) briefly run the container, I find this more convenient, and a little more robust. Note: it's very important to specify --entrypoint="", otherwise the container will start invoking its normal startup routine!
$ docker run --rm -i -a STDOUT --entrypoint="" \
ubuntu:latest sh -c 'head -n 1000 /etc/hostname /etc/*[Rr][Ee][Ll]*'
==> /etc/hostname <==
b243ff33e245
==> /etc/lsb-release <==
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=20.04
DISTRIB_CODENAME=focal
DISTRIB_DESCRIPTION="Ubuntu 20.04.2 LTS"
==> /etc/os-release <==
NAME="Ubuntu"
VERSION="20.04.2 LTS (Focal Fossa)"
ID=ubuntu
ID_LIKE=debian
PRETTY_NAME="Ubuntu 20.04.2 LTS"
VERSION_ID="20.04"
HOME_URL="https://www.ubuntu.com/"
SUPPORT_URL="https://help.ubuntu.com/"
BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/"
PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy"
VERSION_CODENAME=focal
UBUNTU_CODENAME=focal
Here's the same command against "alpine:latest":
docker run --rm -i -a STDOUT --entrypoint="" \
alpine:latest 'sh' '-c' 'head -n 1000 /etc/hostname /etc/*[Rr][Ee][Ll]*'
==> /etc/hostname <==
a8521c768aeb
==> /etc/alpine-release <==
3.13.4
==> /etc/os-release <==
NAME="Alpine Linux"
ID=alpine
VERSION_ID=3.13.4
PRETTY_NAME="Alpine Linux v3.13"
HOME_URL="https://alpinelinux.org/"
BUG_REPORT_URL="https://bugs.alpinelinux.org/"
Note: I add "/etc/hostname" to the list of files to "head" to make sure it finds 2 or more files, to ensure "head" to uses its "==> file <==" output style. Whereas if it only runs against a single file it doesn't print the filename.
Related
$ docker run -it --name systemd-tutorial ubuntu
root#306c0deb6960:~# systemctl
bash: systemctl: command not found
why??
The systemctl utility, which is available by default in Ubuntu, can be used to list services in Ubuntu 22.04 using the command “systemctl –no-pager”.
my version:
root#306c0deb6960:~# cat /etc/*-release
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=22.04
DISTRIB_CODENAME=jammy
DISTRIB_DESCRIPTION="Ubuntu 22.04.1 LTS"
...
why?
Containers, typically used for single -service jobs, typically come without the full systemd suite of service management, which would have trouble running without access to the system dbus, anyway. So, this is kind of expected.
I am trying to install linux header for my ubuntu 18.04 docker image (ubuntu:18.04). Usually I will do sudo apt-get install linux-headers-$(uname -r) in my VM to get the current linux header packages.
But the docker image return the following when I run uname -r
root#0c4e24cca819:/# uname -r
4.19.76-linuxkit
Just wonder which linux header image I should use for ubuntu:18.04 docker image?
Docker by definition runs your current kernel. If you are on a machine whose kernel has not been packaged for Ubuntu then there is no package you can install to get its headers.
Looks like you're on a Mac, so definitely that is the case here. Perhaps you could ask the Docker for Mac maintainers to provide headers for some popular platforms for their kernel, but I suspect they don't want to take on that responsibility.
As a workaround, maybe run Docker inside Linux on e.g. Virtualbox.
enter image description here
nvidia gpu is not available for python3.6, it's only available for python2.7 version.
I'm working on ubuntu, cuda 10.1, and all drivers working properly.
I also tried by creating new python environment but still gpu is available for python, not python3.
what should i do to use the gpu for runing python3 script?
please note that, tensorflow-gpu, torch is already installed and they work on python2, the only problem is that python3 doesn't use the gpu, including jupyter notebook(uses python3).
i use ssh to connect to the server, nvidia docker is already installed.
I was able to solve the issue by using the nvidia docker images
Look for your docker image:
$ docker images
Run the docker image with specified IMAGE ID:
$ docker run --rm -it --runtime=nvidia --net=host -v /<local dir>/:/<destination dir> <IMAGE ID>
$ docker run --rm -it --runtime=nvidia --net=host -v /my_sever_dir/:/notebook 8d78dd1e1q
To access the jupyter notebook, copy the token and paste it on the browser(in the below example, provide your correct ip address and token. The port:8888 could be different if its already taken, for instance try:8889):
http://YOUR_IP:8888/?token=YOUR_TOKEN_FROM_STEP_2_ABOVE
is it possible to run in headless linux, to be exact, linux with no desktop enviroment with GUI from inside docker.
(only if couldt be done differently with x server of some sort, but I would rather run everything within docker)
I want to run GUI only on occasions and I dont want it to share the userspace with the base system programs. Also I dont want to preserve the DE till the next occasion that is needed.
Sure it's possible!
First let's create a docker volume to store the X11 socket:
docker volume create --name xsocket
Now we can create an image with X Server:
FROM ubuntu
RUN apt-get update && \
DEBIAN_FRONTEND='noninteractive' apt-get install -y xorg
CMD /usr/bin/X :0 -nolisten tcp vt1
Let us build it and start it and store the X11 socket in xsocket docker volume:
docker build . -t docker-x-server:latest
docker run --privileged -v xsocket:/tmp/.X11-unix -d docker-x-server:latest
Now we can run a GUI application in another docker container (yay!) and point it to our X server using xsocket volume:
docker run --rm -it -e DISPLAY=:0 -v xsocket:/tmp/.X11-unix:ro stefanscherer/xeyes
If you need input (like keyboard) install xserver-xorg-input-evdev package and add -v /run/udev/data:/run/udev/data since there's no udev in containers by default.
You can even get rid of --privileged flag by granting SYS_TTY_CONFIG capability and binding some devices into container:
docker run --name docker-x-server --device=/dev/input --device=/dev/console --device=/dev/dri --device=/dev/fb0 --device=/dev/tty --device=/dev/tty1 --device=/dev/vga_arbiter --device=/dev/snd --device=/dev/psaux --cap-add=SYS_TTY_CONFIG -v xsocket:/tmp/.X11-unix -d docker-x-server:latest
I'm using the lastest Docker for Windows, which needs Hyper-V to be enabled, and virtualbox cannot be used in this case.
I've installed the the ubuntu container and started it, I want to mount C:\Users\username in the docker container. I've tried the following methods.
docker run -t -i -v /c/Users/username:/mnt/c ubuntu /bin/bash
docker run -d -P --name windows -v C:\Users\username:/mnt/c ubuntu /bin/bash
docker run -t -i -v /c/Users/username:/mnt/c ubuntu /bin/bash
None of them worked. I noticed that /mnt/c was created automatically, but it contained nothing.
Given that Docker for Windows is pretty new, most information I found online was about Boot2Docker or virtualbox, which is useless to me.