Where is the place of specifying automount options for a specific file system (original) (raw)

Zhu, Peter J peter.j.zhu at intel.com
Fri Dec 4 03:29:36 PST 2009

Hey,

Sorry I missed your reply > Using /etc/fstab?? I don't understand. For fixed partition, yes, it's > anaconda's job to manipulate this file do right thing. Yeah, the OS installer typically writes out the /etc/fstab file for swap and other filesystems used for the OS (e.g. /usr). > But for a > hot-plugged device like a USB disk , we shouldn't use this file. We > should do it with something like udev rules, I think. And for your > info, mount show > "(rw,nosuid,nodeve,uhelper=devkit,uid=500,gid=500,shortname=mixed,dmas > k=0077,utf8=1,flush)" for a usb disk. I want to know where are the > mount options from? The way it works is that the desktop session that decides to mount the device (for GNOME, this is Nautilus/GVfs) calls the FilesystemMount() method for the device http://hal.freedesktop.org/docs/DeviceKit-disks/Device.html#Device.Filesyste mMount This method does take an array of mount options to use. The daemon then combines the given mount options with the defaults, see http://cgit.freedesktop.org/DeviceKit/DeviceKit-disks/tree/src/devkit-disks-dev ice.c?id=009#n4277 and checks that forbidden mount options are passed (the user passing the 'dev' or 'suid' mount option would easily give him root, for example). If things check out, we create the mount point and mount the device. GNOME, however never passes any mount options. Presumably the GNOME developers (am I'm one of them - I wrote most of the storage hotplugging code in GNOME) could read mount options from things like GConf (like gnome-mount did) but after thinking a lot about it we decided to not do this - see this bug and this message https://bugzilla.gnome.org/showbug.cgi?id=586708 http://lists.freedesktop.org/archives/devkit-devel/2009-June/000225.html for some details. If it turns out it is needed we can always just change GNOME to pass mount options and if needed we can always read them from things like GConf/GSettings/DConf and provide an UI to edit them. Note that the daemon will always respect the contents of the /etc/fstab file - so if you put in lines like /dev/disk/by-label/MyPhotos /media/MyPhotos vfat shortname=lower,dmask=0000,users 0 0 then it will be used. You can also use the /disk/disk/by-path symlinks to set mount options for any device plugged into a given port. > > I'm curious though - what mount options do you need to change? The > > defaults should work out of the box. > > > Yes, works. Just want to know how it works. OK, good. FWIW, My gut feeling is that if the user needs to pass mount options for mounting local filesystems then the filesystem driver is probably doing something wrong. I really don't think a "edit mount options" in the normal desktop shell experience makes any sense on a modern desktop - we should be able to autodetect things out of the box. Note that Palimpsest Disk Utility and udisks (aka DeviceKit-disks) in the future will provide an UI to edit the /etc/fstab file so the admin can decide that some filesystem should be mounted at boot- and/or plug-in-time. (In addition, there are also plans for Palimpsest/udisks to provide UI to toggle whether things like RAID arrays and LVM Volume Groups should be started at boot- and/or plug-in-time. FWIW, nowadays I don't consider Palimpsest part of the normal desktop shell - it is a utility used by admins to set up storage for workstations and servers. It is still useful for the desktop shell experience but the desktop shell already provides simpler tools (built on exactly the same code) for formatting and starting/stopping things like RAID.) I hope this clarifies. Thanks, very very clear.

Thanks, David

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