Le 11/03/2019 à 16:48, [email protected] a écrit :
Didier:
Le 10/03/2019 à 11:22, [email protected] a écrit :
Since nowadays the kernel can provide devtmpfs, what is the role of
udev et al apart from handling usb devices ?
   1) Change owner, group and permissions because the kernel defaults
everything to root.root and (I guess) 0600
   2) Create and populate /dev/disk/by-*, which is sometimes usefull
on a desktop or laptop.
   3) Rename network devices (for people who want that)
   The first 2 items might be done by monitoring /dev with inotify.
This must be checked though because, in principle, inotify only reports
interactions with the VFS issued from userspace, which is why it doesn't
work on /sys and /proc. Inotify works fine when /dev and
/dev/disk/by-label are popluated by udev, but I didn't check with
devtmpfs. We would then resort to reading the netlink.
Isn't the above moot if you have a no usb devices and static dev:
1) changing owner/group/permissions are persistent, i.e. set it once
and be done with it
SInce device files are created when the devices are discovered, you
start from an empty /dev at boot; therefore you need to reassign
owner/group/permission every time. If nothing ever changes, you can of
course do it with a simple script invoked in rc.local.
2) isn't that mostly useful for if you have lots of disks, say more than 5.
If you just have one or two, you don't need that.
Also that could be generated by a script which you run manually when
needed.
I could imagine all these owner/group/permissions and symlinks
might be managed by a generic script run at boot. But there are devices
which you insert asynchronously, like USB memory sticks, SD cards or
backup disks. It is very convenient, in a laptop/desktop to see the
partition name and label pop up on the screen and only need a mouseclick
to open it.
Didier
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