How can I delete files on a read-only file system?

Question

I have an encrypted .dmg file with some useless files that I need to delete to make space. How can I delete them without having to convert them into a read write system and then back? (Would take 4~5 hours).

Like I said, it's read only so sudo rm -rf tells me that It can't delete it due to it being a read only file system.

Solution

A read-only file system can only be read (therefore it is named read-only).

To delete files on this file-system you have to remount it read-write.

Comments

[taliezin]

Check if this can help you.

[Octopus]

Deleting files from the middle of a large encrypted file will in itself be a time consuming task, even if it were a writeable system. It will have to be deconstructed and reconstructed in any case.

[Romulus Urakagi Ts'ai]

Looks like it's not so simple as to mount *.dmg read/write. They need to be unpacked and reconstructed, just like tar archives.