What is the difference between /var/lib/containers/storage/tmp and /var/tmp?

[BlackHole1]

I noticed that there is a tmp directory under /var/lib/containers/storage/, but I couldn't find any documentation or information about this directory. The imageCopyTmpDir defaults to using the value of the TMPDIR environment variable (or sets it to /var/tmp if it's not defined). I would like to know if it's possible to set imageCopyTmpDir to /var/lib/containers/storage/tmp and if there would be any issues if it's set to /tmp or /run/tmp.

[BlackHole1]

PTAL @rhatdan 🙇‍♂️

[rhatdan]

I don't believe it is used.

[rhatdan]

I believe https://github.com/containers/podman/pull/20635/files should remove the directory if it exists and remove it, if it was precreated.

[BlackHole1]

Thank you for your answer!

[BlackHole1]

Another question: Can I set the imageCopyTmpDir path to /run directory? I’m not sure if there will be any instability issue if its contents are not preserved after each system startup. @rhatdan

[rhatdan]

I don;t think that would be a good idea, since this is space limited, and some images are huge. Also not sure if you could do this other then potentially setting the TMPDIR environment to point at a subdir of /run/

[BlackHole1]

Sorry for the confusion in my previous description. What I meant to say is: If the files in the ImageCopyTmpDir directory are automatically deleted after each system reboot, will there be any issues (similar to the mechanism of the /run directory)?

I just saw the discussion in #20635, which raises another question. If I set ImageCopyTmpDir to storage, it seems that the content in /var/lib/containers/storage/tmp will never be deleted. I’m not sure if this is reasonable (maybe it should be changed to: d /var/lib/containers/storage/tmp 0777 root root 30d).

[rhatdan]

Doesn't
D! /var/lib/containers/storage/tmp 0777 root root 30d

Delete all files in /var/lib/containers/storage/tmp on reboot?

[BlackHole1]

Doesn't
D! /var/lib/containers/storage/tmp 0777 root root 30d

Will this cause the folder to grow indefinitely? Is this expected?

[rhatdan]

Folder should only grow if something fails during an action, ordinarily temporary files are deleted. With this command, the files that are older then 30 days will be deleted on reboot.

[BlackHole1]

Thank you for your response, which has helped me understand the purpose of ImageCopyTmpDir. I will explain my understanding, and please correct me if I am wrong.

If the TMPDIR environment variable is not set, ImageCopyTmpDir will use the /var/tmp directory, which is managed by tmpfile.d, and files inside will be deleted after 30 days. However, if ImageCopyTmpDir is set as storage, it will use the /var/lib/containers/storage/tmp directory, and any file content in this directory will never be automatically deleted (because tmpfile.d does not have the Age field set for this folder by default).

ImageCopyTmpDir will only write certain files to the directory in the event of certain failures. Based on this, I can safely delete the contents of the ImageCopyTmpDir directory (for example, after the system starts up).

[rhatdan]

My understanding of the tmpfile.d is without the Age field, all content will be deleted on a Reboot. I believe you can safely delete the contents at system start, or whenever you don't have any podman commands running.

[BlackHole1]

Thank you so much for your answer!

[BlackHole1]

#20635 (comment)