On Tue, Dec 3, 2013 at 5:22 PM, Jc García <jyo.gar...@gmail.com> wrote: > 2013/12/3 Canek Peláez Valdés <can...@gmail.com>: >> On Tue, Dec 3, 2013 at 12:06 AM, Canek Peláez Valdés <can...@gmail.com> >> wrote: >>> On Mon, Dec 2, 2013 at 10:34 PM, Jc García <jyo.gar...@gmail.com> wrote: >>>> 2013/12/2 William Kenworthy <bi...@iinet.net.au> >>>>> >>>>> You are looking far too deep .... >>>>> >>>>> >>>>> just rsync -avP to /newusr >>>> >>>> +1 >>>> I have done this more or less the same way >>>>> >>>>> reboot to livecd >>>>> >>>>> rsync again with --delete to update ... takes a only few seconds this >>>>> time - minimal downtime :) >>>>> mv /usr /oldusr >>>>> mv /newusr /usr >>>>> reboot >>>> >>>> >>>> Let's make this thread more interesting, would it be possible to do >>>> this without a reboot? ie: going single user mode, kill anything that >>>> might still be running from usr, umount /usr, mount it to /mnt, rsync >>>> -avP to usr, going again into runlevel 3 or 5. >>>> Obviously not possible if running systemd. >>> >>> I'm not so sure it's not possible. Perhaps it's even easier. >> >> So, yeah, I think it's easier with systemd. You just: >> >> 1. systemctl isolate emergency.target >> 2. log in again (all the normal gettys are killed with the above command) >> 3. rsync -PvasHA /usr/ /newusr/ >> 4. mv /usr /oldusr # mv is on /bin, so no problems here >> 5. mv /newusr /usr >> 6. rm -rf /oldusr (to make sure nothing uses it anymore) >> 7. systemctl isolate multi-user.target >> 8. You have your system again. >> > Nice, I thought systemd residing within /usr would be the limitation, > i haven't used systemd very much , so i don't really know it's options, > but later after thinking about it, i thought that using the initramfs > would be a way to go, > but as i understand here systemd already has an option to make use of it.
Yeah, you can create an initramfs with dracut that uses systemd; the initramfs mounts /usr, and then handles back control to the systemd instance in it. When shutting down, the inverse occurs; the systemd in /usr handles back control to the systemd in the initramfs, which in turns shutdowns the machine. I don't know exactly how problematic would be for a complex setup (/usr using LVM+cryptfs+mdraid, for example), but if the necessary tools are available in the initramfs, then I think it could be done. Of course, the simplest and easiest thing to do is to use a live CD. Regards. -- Canek Peláez Valdés Posgrado en Ciencia e Ingeniería de la Computación Universidad Nacional Autónoma de México
