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I read on the man page

defaults Use default options: rw, suid, dev, exec, auto, nouser, async, and relatime.

Do the options set depend on a mounted filesystem or not?

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up vote 2 down vote accepted

In the man page, defaults is listed under Filesystem Independent Mount Options, which means it doesn't depend on the filesystem type.

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Oh, I'm sorry, didn't notice it – Maksim Dmitriev Apr 28 '13 at 17:22
Now you do, no need to be sorry :) – phunehehe Apr 28 '13 at 17:28

Well, what do you mean by "depend on the mounted file system" ?

To begin with, this line in the man page defines an option called defaults. This option defaults is available for all file systems as indicated by the section heading. It stands exactly for the set of options listed in the definition of defaults. You may see it as a replacement for that list.

Then, a default option may be surperseded by other considerations. For example, if you use the option default for a DVD drive, you will end up with option ro rather than rw when the drive is mounted because DVDs have read-only file systems (the file system does not exists yet when you write). A file containing the image of an ISO 9660 file system will also be mounted ro with a loop device. I do not know for an ext4 file system image (I still have to try it).

Also, if you use default and follow it with other options, it may cancel some of the options set by default. For example the option owner will cancel many.

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