On Thu, Mar 31, 2011 at 05:04:27PM +0200, Thomas Bächler wrote: > Am 31.03.2011 16:44, schrieb Tom Gundersen: > > On systemd systems with initramfs and LVM used, packagers must > > make sure, that the systemd and initramfs versions match. The initramfs > > needs to create the /run/ mountpoint for udev to store the data, and > > mount this tmpfs to /run in the rootfs, so the that the udev database > > is preserved for the udev version started in the rootfs. > > *** > > > > The last paragraph is admittedly referring to systemd, but I think > > this is not important (I think the same case would apply to any init > > system mounting /run). Here I get the impression that there is > > something valuable in the udev database that could and should be > > preserved from initramfs to normal init (I don't fully understand what > > is happening here, so maybe it does not apply to Arch). > > > >> I was thinking with regard to mdadm now: Maybe mdadm stores some > >> valuable data there. > > > > They certainly store something in /run, but I don't know what happens > > if we throw it away at the end of initramfs. > > > >>From all the discussions on this topic I really got the impression > > that /run is supposed to be created in the initramfs and then > > preserved until shutdown. Maybe it is worth having a look at what > > dracut is doing? > > We can do that easily (identical as the /proc, /sys, /dev stuff). > However, prepare to run into problems when the initramfs udev version > does not match the version in the system. >
Shouldn't be a problem unless there's a format change, as udev can convert the DB. Relevant snippets from dmesg on my work VM (which i abuse mercilessly): udev[36]: starting version 166 <30>udev[462]: converting old udev database <30>udev[462]: starting version 167 dave
