I'm trying to figure out the version of Ubuntu being used in a docker container.
This Verfiy the version of ubuntu running in a Docker container mentions cat /etc/lsb-release which gives:
cat: can't open '/etc/lsb-release': No such file or directory
and uname -r gives:
3.13.0-119-generic
FWIW, uname -a gives:
Linux <container id> 3.13.0-119-generic #166-Ubuntu SMP Wed May 3 12:18:55 UTC 2017 x86_64 Linux
Any ideas what version of Ubuntu it might be? Or how else I can find this out?
Try lsb-release -a or cat /etc/issue
Just docker history --no-trunc your_image will show, among other things the FROM ... line
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 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.
I was trying to run a docker container with ubuntu:16.04 (on a ubuntu 18.04 machine) with the following command:
docker run -i -t --name ubuntu ubuntu:16.04 /bin/bash
Running this command attaches me to a container. But when I check the kernel information with uname -a, it shows that the current kernel is Ubuntu 18.04. Following is the result I get:
Linux 1ac6c3456e2a 5.3.0-40-generic #32~18.04.1-Ubuntu SMP Mon Feb 3 14:05:59 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux
What could be the cause?
Docker uses host OS kernel, there is no custom or additional kernel inside container. All containers which run on a machine are sharing this "host" kernel.
Please read this for more detail.
So #32~18.04.1-Ubuntu SMP Mon Feb 3 14:05:59 UTC 2020 in the output of uname -a is actually the Kernel version of the host machine.
To verify that you are running Ubuntu 16:04, run cat /etc/os-release. It will provide you details about your OS.
want to code a script that is for multiple linux distributions.
Also want to add commands that check, and if not exist install some packages.. So, need a solution to ckeck Dist name (like Debian or RedHat) to execute the right command for this Dist.
I have tryed "lsb_release" but is this working all the follow dists? : Debian / Ubuntu | Red Hat / Fedora / Suse / Cent OS" If yes, any idea where i can get the lsb_release output from all the Dists above?
in Debian I get this from lsb_release -a 2>/dev/null | grep Distributor:
Distributor ID: Debian
at Rasberry, I get this:
Distributor ID: Raspbian
but what about other Distributions?
Yes, the lsb_release should print the distribution information after installing the required package.
e,g:
On debian based distro:
apt-get install lsb-release
On RHEL based distro:
yum install redhat-lsb-core
or
yum install redhat-lsb
Alernative method : You can get the distribution information through:
On debian based disto
cat /proc/version
cat /etc/issue
cat /etc/issue.net
cat /etc/lsb-release
cat /etc/os-release
On RHEL based distro :
cat /proc/version
cat /etc/centos-release
cat /etc/lsb-release
cat /etc/redhat-release
cat /etc/system-release
seems that all modern linux distributions have /etc/os-release file with ID=distribution (unfortunately have no Raspberry around to test).
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.