I trying to figure out what the following Mountoption for (v)FAT exactly does (in Linux):
allow_utime=### -- This option controls the permission check of mtime/atime.
20 - If current process is in group of file's group ID, you can change timestamp. 2 - Other users can change timestamp. The default is set from `dmask' option. (If the directory is writable, utime(2) is also allowed. I.e. ~dmask & 022) Normally utime(2) checks current process is owner of the file, or it has CAP_FOWNER capability. But FAT filesystem doesn't have uid/gid on disk, so normal check is too unflexible. With this option you can relax it.
Question: What does this (above) mean?
Trying to look it up I endend with the C code which doesn't help me a lot, so neither this nor
man 2 utime (as mentioned) help me much at the moment. I'd love to use the source…
utime: The utime() system call changes the access and modification times of the inode specified by filename to the actime and
modtime fields of times respectively.
I read this as: Enable to change timestamps. Super Extra Kudos for you who can give an actual example of how to use this Mountoption (