X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?p=elogind.git;a=blobdiff_plain;f=FAQ;h=bd9d63a4d50ef7e54f8b7041aeb1f8587d146b63;hp=a3bec17408f2e722fbe2155326faebb51bca8148;hb=69348b66ff4163a2fbf974bde649e5bc963462b4;hpb=786f9231961cc12e59cce3e3ad117ad976adf6f5 diff --git a/FAQ b/FAQ index a3bec1740..bd9d63a4d 100644 --- a/FAQ +++ b/FAQ @@ -23,7 +23,7 @@ A: To quote Al Viro (Linux VFS kernel maintainer): - the former had stayed around for many months with maintainer claiming that everything works fine - the latter had stayed, period. - - the devfs maintainer/author disappeared and stoped maintaining + - the devfs maintainer/author disappeared and stopped maintaining the code. Q: But udev will not automatically load a driver if a /dev node is opened @@ -72,10 +72,6 @@ A: udev is entirely in userspace. If the kernel supports a greater number Q: Will udev support symlinks? A: Yes, It now does. Multiple symlinks per device node too. -Q: How will udev support changes to device permissions? -A: On shutdown, udev will save the state of existing device permissions to - its database, and then used the on the next boot time. - Q: How will udev handle the /dev filesystem? A: /dev can be a ramfs, or a backing filesystem. udev does not care what kind of filesystem it runs on. @@ -84,6 +80,33 @@ Q: How will udev handle devices found before init runs? A: udev will be placed in initramfs and run for every device that is found. Work to get this implemented is still underway. +Q: Can I use udev to automount a USB device when I connect it? +A: Technically, yes, but udev is not intended for this. Projects that do + automount hotplugged storage devices are: + * Usb-mount http://users.actrix.co.nz/michael/usbmount.html + * devlabel http://linux.dell.com/projects.shtml#devlabel + + Alternatively, it is easy to add the following to fstab: + /udev/pendrive /pendrive vfat user,noauto 0 0 + + This means that users can access the device with: + $ mount /pendrive + And don't have to be root but will get full permissions on /pendrive. + This works even without udev if /udev/pendrive is replaced by /dev/sda1 + +Q: Are there any security issues that I should be aware of? +A: When using dynamic device numbers, a given pair of major/minor numbers may + point to different hardware over time. If a user has permission to access a + specific device node directly and is able to create hard links to this node, + he or she can do so to create a copy of the device node. When the device is + unplugged and udev removes the device node, the user's copy remains. + If the device node is later recreated with different permissions the hard + link can still be used to access the device using the old permissions. + (The same problem exists when using PAM to change permissions on login.) + + The simplest solution is to prevent the creation of hard links by putting + /dev in a separate filesystem (tmpfs, ramfs, ...). + Q: I have other questions about udev, where do I ask them? A: The linux-hotplug-devel mailing list is the proper place for it. The address for it is linux-hotplug-devel@lists.sourceforge.net