use scenario for overlay FS

Hi Neil,

Regarding the overlayfs implementation, I am interested in overlaying two squashfs file systems, read-only, and running into a problem with location of the work directory:

"overlayfs: workdir and upperdir must reside under the same mount"

Since the upper directory is read-only, and it is mounted on a partition as such, having writable work directory is not possible. Any suggestions on how to utilize overlayfs in this scenario?

I feel this restriction is overkill for the feature.

--
Thanks,
Iyad

I thought upperdir is now optional but must be read-write if one is

Quoted 12 lines

Hi Neil,

Regarding the overlayfs implementation, I am interested in overlaying two squashfs file systems, read-only, and running into a problem with location of the work directory:

"overlayfs: workdir and upperdir must reside under the same mount"

Since the upper directory is read-only, and it is mounted on a partition as such, having writable work directory is not possible. Any suggestions on how to utilize overlayfs in this scenario?

Quoted 5 lines

I feel this restriction is overkill for the feature.

--
Thanks,
Iyad

I thought upperdir is now optional but must be read-write if one is specified. Therefore if you want the whole stack read-only specify only lowdirs and skip the upperdir. Correct me if I am wrong.

Alex

I have two file systems that I need to create a union for. The upperdir overrides the lowerdir, hence replacing its content. Therefore, regardless if the upperdir is optional, I do need it in this use case.

Per the documentation:

"A read-only overlay of two read-only filesystems may use any
filesystem type."

I understood that my use case is possible. However, it does contradict the actual implementation,

"overlayfs: workdir and upperdir must reside under the same mount"

and your statement, of course.

Thanks,
Iyad

Quoted 5 lines · A. Wan

I thought upperdir is now optional but must be read-write if one is specified. Therefore if you want the whole stack read-only specify only lowdirs and skip the upperdir. Correct me if I am wrong.

Alex