rw vs. umask in mount call, and coditional mounting
Posted on 2004-10-07
Although I know the answer to the first part of this question, the
issue is still not 100% clear. The first question is, what is the
difference between the option rw vs. umask in a mount call? Let me
explain the entire situation since it leads to question number 2.
I have a usb card reader that when plugged into my system is either
recognized as /dev/sda1 or sometimes (if I already have something
plugged in) as /dev/sdb1.
This card is formatted as fat32 so that I can write to it using Linux.
I have disabled supermount from loading this drive in /etc/fstab
because I don't like supermount for some reason I forgot a while ago.
Ok, so my /etc/fstab reads
/dev/sda1 /mnt/flashcard vfat user,umask=000,rw 0 0
The thing is that I don't need rw to be able to write to this mount
point. The mount man pages say the following about the rw option:
rw Mount the file system read-write.
That is it. I guess my question goes a bit further than the basic
difference. Not only do I want to know what is the difference between
rw and umask but also where can I get this information from my system
so that I don't have to bother people on the internet. I've tryied
the info call and in it there is no mention that the rw option is
valid for mounting vfat nor for any of the explicitly mentioned
filesystems. The documentation, in my opinion, does not explain when
and where to use the rw option. Any suggestions?
Although it may be that supermount would take care of this, I would
like to know if there is a way to conditionally mount devices. The
reason for this is that, like I said earlier, my card reader is
mounted on /dev/sda1 or /dev/sdb1. Would there be a way to have a
mount definition in /etc/fstab so that it figures out where the card
reader is recognized?