--volume command works when arguments are reversed

General
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1

Running a mariadb container with system variables configured using a volume doesn’t work when I pass in the configuration file as a volume using the documented arguments

The command that doesn’t work:

docker run --name mariadatabase --env MYSQL_ROOT_PASSWORD= --env MYSQL_ALLOW_EMPTY_PASSWORD=1 --env MYSQL_DATABASE=spp -v */home/king_julien_13/docker/pgdp.cnf:/etc/mysql/conf.d* -p 3306:3306 mariadb:10.5.9

Output:

docker: Error response from daemon: failed to create task for container: failed to create shim task: OCI runtime create failed: runc create failed: unable to start container process: error during container init: error mounting "/home/king_julien_13/docker/pgdp.cnf" to rootfs at "/etc/mysql/conf.d": mount /home/king_julien_13/docker/pgdp.cnf:/etc/mysql/conf.d (via /proc/self/fd/7), flags: 0x5000, data: context="system_u:object_r:container_file_t:s0:c154,c963": not a directory: unknown: Are you trying to mount a directory onto a file (or vice-versa)? Check if the specified host path exists and is the expected type.

But when I run the same command with the -v arguments reversed (container-path:host-path), it works like a charm. This stackoverflow answer is what got me into the working command, but I’m running docker entirely on my host, unlike what is mentioned in the answer

Linux Distro: Fedora 40
Docker Version: Docker version 24.0.5, build %{shortcommit_cli}

Edit-Note:: I tried doing the same thing with podman and the same behaviour happens

2

What are the stars supposed to be?

3

Nothing. It was my zsh shell that had those, but they don’t do anything

4

If these are part of your command they definitely do not do nothing. Are they or did you add them just for highlight in this forum post?

5

They’re not a part of the command. I’ve ran the commands multiple times even without the asterisk ( i didn’t even notice if before), it’s the same result

6

Looks like you try to bind a host file into a container folder.

If I am right, this should work: /home/king_julien_13/docker/pgdp.cnf:/etc/mysql/conf.d/pgdp.cnf

Update: yup, it’s the case:

docker run --rm  --entrypoint stat mariadb:10.5.9 /etc/mysql/conf.d
  File: /etc/mysql/conf.d
  Size: 24              Blocks: 0          IO Block: 4096   directory
Device: d1h/209d        Inode: 76877282    Links: 2
Access: (0755/drwxr-xr-x)  Uid: (    0/    root)   Gid: (    0/    root)
Access: 2024-09-18 16:37:27.848104419 +0000
Modify: 2021-04-24 00:32:42.000000000 +0000
Change: 2024-09-18 16:37:27.844104393 +0000
 Birth: -
1 Like
7

It does work. Do you have any explanation on this one?

It bugs me to think reversing the arguments work but that method also works.

8

That is already the explanation: you are trying to bind a file into a folder. You can bind a file into a file, or a directory into a directory,. The host source and the container target must be of the same type: either both files, or both directories.

9

Sorry I didn’t say it correctly. I understood that part.

What I can’t get my head around is how reversing the argument works? I couldn’t find anything relevant on my extensive google search

10

Because either one of both or both don’t exist, and docker then creates the missing part as right type. I assume if both don’t exist, that docker will bind the fresh created host directory into the created container directory.

1 Like