echo $UID gives host ID and not container root user ID (docker/linux)-CodePudding

My current user ID on my host (ubuntu) is:

$ echo "Host UID = $UID"
Host UID = 1000

But when I run this docker container I get the same UID:

$ docker run --rm --name test-container centos:7.9.2009 /bin/bash -c "echo $UID"
1000

If I instead run the container interactively I get 0 as expected:

$ docker run -it --rm --name test-container centos:7.9.2009
[root@4a79cb82abec /]# echo $UID
0

Why do I get the wrong (my host user) UID when I run the container with /bin/bash -c "echo $UID"?

CodePudding user response：

You want to get UID from inside the container. However the variable UID is expanded on the host's shell itself. Use single quote to avoid it getting expanded:

docker run --rm --name test-container centos:7.9.2009 /bin/bash -c 'echo $UID'