Re: [systemd-devel] booting A/B rootfs
On Thu, Oct 09, 2014 at 06:13:01AM +0200, Darko Luketic wrote: Hi, I have limited knowledge of the boot process. I'm wondering if the following is possible with systemd. Imagine you have 2 rootfs partitions. You build a new rootfs on a security update or when a new version of a listed package that has dependencies is released and extract this on either A or B partition (A if B is the current rootfs, B if A is the current rootfs) The idea is, with systemd you can isolate targets. I assume you could shutdown all services so that nothing but systemd is running. Then unmount the current rootfs and mount the new rootfs and boot to default target. All without needing to poweroff or physically reboot the system. Only if you install a new kernel a real reboot would be required. Would this be possible with systemd in its current state? Why? Minimal downtime and if the new rootfs fails for whatever reason you could revert to the old rootfs but have a consistent userspace. Or you could run a testing system and if the new image reports no errors flag it stable and distribute to clients. And if this is possible, what if... you could shutdown the current running kernel and boot a new kernel which would in turn again run init and boot targets. CoreOS and ChromeOS do this today, but you need to do this with the bootloader, not at the init level. systemd it too high-level to do this, sorry. good luck, greg k-h ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel
Re: [systemd-devel] booting A/B rootfs
On Thu, Oct 09, 2014 at 06:13:01AM +0200, Darko Luketic wrote: Hi, I have limited knowledge of the boot process. I'm wondering if the following is possible with systemd. Imagine you have 2 rootfs partitions. You build a new rootfs on a security update or when a new version of a listed package that has dependencies is released and extract this on either A or B partition (A if B is the current rootfs, B if A is the current rootfs) The idea is, with systemd you can isolate targets. I assume you could shutdown all services so that nothing but systemd is running. Then unmount the current rootfs and mount the new rootfs and boot to default target. All without needing to poweroff or physically reboot the system. Only if you install a new kernel a real reboot would be required. Would this be possible with systemd in its current state? Sure, read about switch-root in systemctl(1). Why? Minimal downtime and if the new rootfs fails for whatever reason you could revert to the old rootfs but have a consistent userspace. Or you could run a testing system and if the new image reports no errors flag it stable and distribute to clients. And if this is possible, what if... you could shutdown the current running kernel and boot a new kernel which would in turn again run init and boot targets. Sure, see kexec in systemctl(1). Good luck, Zbyszek ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel
Re: [systemd-devel] booting A/B rootfs
On Thu, 09.10.14 06:13, Darko Luketic (i...@icod.de) wrote: Hi, I have limited knowledge of the boot process. I'm wondering if the following is possible with systemd. Imagine you have 2 rootfs partitions. You build a new rootfs on a security update or when a new version of a listed package that has dependencies is released and extract this on either A or B partition (A if B is the current rootfs, B if A is the current rootfs) The idea is, with systemd you can isolate targets. I assume you could shutdown all services so that nothing but systemd is running. Then unmount the current rootfs and mount the new rootfs and boot to default target. All without needing to poweroff or physically reboot the system. Only if you install a new kernel a real reboot would be required. Would this be possible with systemd in its current state? This has been requested before, but is currently not nicely supported, but I am open to adding some support for this. Note though that you probably need to do more than just stopping all services, you need to at least flush out /run, too, plus some other things like /dev/shm, or the sysvipc objects. The part of this that I think might be suitable for direct integration into systemd is the above plus maybe high-level support in systemctl to get a new verb for rebooting this way. The swapping of the partitions though probably something to do externally, integrated in the same way as the current dracut/initrd shutdown logic is integrated, which disassembles the root disk: after systemd did everything it could do it transitions back into the initrd which then does what it needs to do. In fact, you probably could use the initrd logic for this already, just place a script /run/initramfs/shutdown, do the flushing of /run+sysv manually, and then simply reexec systemd again. Lennart -- Lennart Poettering, Red Hat ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel
[systemd-devel] booting A/B rootfs
Hi, I have limited knowledge of the boot process. I'm wondering if the following is possible with systemd. Imagine you have 2 rootfs partitions. You build a new rootfs on a security update or when a new version of a listed package that has dependencies is released and extract this on either A or B partition (A if B is the current rootfs, B if A is the current rootfs) The idea is, with systemd you can isolate targets. I assume you could shutdown all services so that nothing but systemd is running. Then unmount the current rootfs and mount the new rootfs and boot to default target. All without needing to poweroff or physically reboot the system. Only if you install a new kernel a real reboot would be required. Would this be possible with systemd in its current state? Why? Minimal downtime and if the new rootfs fails for whatever reason you could revert to the old rootfs but have a consistent userspace. Or you could run a testing system and if the new image reports no errors flag it stable and distribute to clients. And if this is possible, what if... you could shutdown the current running kernel and boot a new kernel which would in turn again run init and boot targets. ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel
