Jonathan Callen wrote: > On 06/09/2016 10:00 AM, Dale wrote: >> waltd...@waltdnes.org wrote: >>> On Thu, Jun 09, 2016 at 08:16:57AM -0500, Dale wrote >>>> k...@aspodata.se wrote: >>>>> Dale: >>>>> ... >>>>>> Can a system even boot without udev? >>>>> Yes, use sys-fs/static-dev (unless you have some special boot >>>>> requirements). >>>> Well, I was talking about if udev was removed and then a reboot >>>> was done. I would think it would boot to a certain point then when >>>> whatever started and needed devices to be created in /dev, it would >>>> start failing. I suspect this would vary depending on the install >>>> as well. >>> You need *A* device-manager. You can use udev, eudev, static-dev, >>> mdev, whatever, but you need something. Mind you, some software assumes >>> or requires udev/eudev. >>> >> >> What I was referring to was if during this switch from udev to eudev, >> someone rebooted without any dev manager at all. In other words, emerge >> -C udev and then reboot before emerging eudev or some other dev >> manager. I suspect that would get interesting pretty quick. >> >> Dale >> >> :-) :-) >> >> > Actually, you no longer need a user-space device manager at all, unless > you want to be able to access device nodes under /dev as a user that > isn't UID=0 or has CAP_DAC_OVERRIDE. The kernel provides a devtmpfs > filesystem that will have every single device node that udev used to > create (udev no longer even creates the devices -- it just relies on > devtmpfs doing so), but most of them will be owned by 0:0 (root:root) > with permissions 0600; excepting certain nodes like /dev/null or > /dev/zero, which will be owned by 0:0 with permissions 0666. One other > thing that udev does that you might rely on is to create symlinks like > /dev/disk/by-label/*, which can be used by mount(8) if you specify > LABEL=foo in /etc/fstab. The only other things that I'm aware of udev > doing is to rename network devices and (possibly) to notify other > applications of changes, somehow (but I'm not sure that it actually does > that). > > If you don't actually need any of that (you are working on an embedded > system where you only need root anyway, for instance), then you can just > use a bare devtmpfs without a device manager changing permissions, > adding links, etc. >
That's interesting to read. I recall reading about the devtmpfs in the kernel but thought that was for just the very early stages of booting, reading /boot to get the kernel and such things required to start the boot process. I figured once it got started, it would eventually get to a point and sort of hang up because it couldn't find devices to read to keep going. Interesting. Still don't want to test the theory tho. ;-) Dale :-) :-)
