RFC: Reboot behavior for kexec-tools package
Hello, I implemented automatic kexec reboot support to kexec-tools package many years ago when Debian used init. It worked well except for some corner cases. To support this, I also added a package config option to enable kexec reboots on reboot command. Since Debian started using systemd, automatic kexec reboot had been hit or miss depending upon the changes in systemd. I got it back to working state by requiring users to do kexec reboots using "systemctl kexec". Now Debian has switched to systemd fully and I am removing init scripts from kexec-tools package. Systemd maintainers made a change to systemctl command around 2021 that caused "systemctl kexec" to no longer work the same way again. In short, systemctl now has taken over the task of loading a kexec kernel which was previously delegated to systemd service provided by kexec-tools. systemctl loads kexec'able kernel only on the systems that support boot loader spec which Debian does not. Now kexec-tools package no longer has working automatic kexec reboot. To solve this problem in a reliable and consistent way, I am considering changing the way kexec reboots are handled by kexec-tools package. Current behavior (when it worked) is: - If config option "Should kexec-tools handle reboots?" is set to true, a reboot command will cause a kexec reboot. - With config option "Should kexec-tools handle reboots?" set to true, a cold reboot requires using the command "coldreboot" which is a script installed by kexec-tools package. I want to change the behavior to: - No package config option to do automatic kexec reboot. - "reboot" command causes a cold reboot - Use "kexec-reboot" command to do a kexec reboot. "kexec-reboot" is a script installed by kexec-tools package. - kexec-tools package no longer provides coldreboot script which is no longer necessary. Any comments/feedback? I intend to proceed with implementing new behavior next week after Wednesday unless there are objections or other ideas. Thanks, Khalid
Re: RFC: Reboot behavior for kexec-tools package
On 9/22/23 2:01 PM, Luca Boccassi wrote: On Fri, 22 Sept 2023 at 20:41, Khalid Aziz wrote: Any comments/feedback? I intend to proceed with implementing new behavior next week after Wednesday unless there are objections or other ideas. Hi, In the next version of systemd, due in trixie in a couple of months, we are going to move the kexec-if-loaded behaviour from systemctl to logind itself. Also, we are going to integrate it with the new soft-reboot feature, so that it also automatically soft-reboots if a new rootfs has been loaded. So I would recommend to do no automation at all in kexec-tools, and let systemd handle it, so that it can be integrated with other reboot types and so on. Thanks. Hi Luca, I am planning to include a new script in kexec-tools package which will be installed as /sbin/kexec-load-kernel. This script uses /etc/default/kexec to determine which kexec kernel to load and loads it ready for kexec reboot. My plan was to also include a kexec-reboot script which simply does "/sbin/kexec-load-kernel; /usr/bin/systemctl kexec". Neither of those automates kexec reboots but I can leave the kexec-reboot script out if that works better with upcoming systemd changes. kexec-load-kernel just makes the task of loading a kexec image more user-friendly. Opinion? Thanks, Khalid
Re: RFC: Reboot behavior for kexec-tools package
On 9/22/23 4:26 PM, Michael Biebl wrote: Am 22.09.23 um 21:40 schrieb Khalid Aziz: I want to change the behavior to: - No package config option to do automatic kexec reboot. - "reboot" command causes a cold reboot - Use "kexec-reboot" command to do a kexec reboot. "kexec-reboot" is a script installed by kexec-tools package. - kexec-tools package no longer provides coldreboot script which is no longer necessary. Any comments/feedback? I intend to proceed with implementing new behavior next week after Wednesday unless there are objections or other ideas. I assume you are aware of https://github.com/systemd/systemd/issues/15029 ? Hello Michael, Thanks for pointing that out. Yes, I have seen it and I have been working on finding a working solution for Debian. The kexec image loader in systemctl works with systems that create a boot loader spec file which Debian doesn't. In the absence of boot loader spec file, you get that message. The script I am adding, kexec-load-kernel, allows systemctl kexec to work if one runs this script before calling systemctl kexec. Since we have more automation coming to systemd in trixie, I am going to limit kexec-tools package to providing only helper scripts to load a kernel and call systemctl kexec. Hopefully we will have a working reliable solution with that in place. Thanks, Khalid
