Re: [systemd-devel] About systemd in initrd support
On Sat, 23.08.14 13:46, Luca Bruno (lethalma...@gmail.com) wrote: I'm going to do an experiment with NixOS: replace the whole current initrd process made of scripts and hooks with systemd. Before doing any work however I'd like to hear whether systemd in initrd is still wanted in the future, or there's any possible idea about dropping this support. Of course, this is absolutely somethign we support. In fact, this is how Fedora and suchlike boot since quite some time, and Dracut supports it out-of-the-box. Also, apart arch linux, is there any other OS that you know using systemd for the whole initrd process? Everything Dracut-based, including Fedora, RHEL7 and similar. Lennart -- Lennart Poettering, Red Hat ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel
Re: [systemd-devel] About systemd in initrd support
Thank you all for the replies. After the first answers I've ported the initrd to systemd (only the basic stuff, no luks, lvm, etc.) and works very fine. Except one thing, that I hoped to find in dracut but does not seem to do anything special about it. It just goes through switch-root it seems. As I understood it, systemctl switch-root will either run the specified init, or exec to the systemd in the new root. Looking a little through the code, it seems to do some kind of state-passing that I still have to study (--switched-root --deserialize etc.). Problem: in NixOS we need to run a further stage in the new root, before starting systemd. For example /etc is a symlink to a configuration tree which gets created at boot (we call it activation), and so on. Our init script activates the NixOS system and ultimately exec to systemd. initrd init - setup some env vars and mount points - systemd/initrd - switch-root - system activation script - systemd. Questions: 1) What are the advantages to let switch-root exec to systemd directly? Does executing it from our init is the same thing? 2) In case it's not the same thing, where is the best place to run that script? As a service in the new-root systemd? Thanks. Best regards, ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel
Re: [systemd-devel] About systemd in initrd support
As you already mentioned, you'd have to make sure you manage to pass through the state correctly. Thanks. Is there any docs I can read about this or just read the code? It appears that systemd dumps the state into a file, and afterwards it's passed to the new systemd instance. ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel
Re: [systemd-devel] About systemd in initrd support
On Mon, 25.08.14 21:04, Luca Bruno (lethalma...@gmail.com) wrote: Thank you all for the replies. After the first answers I've ported the initrd to systemd (only the basic stuff, no luks, lvm, etc.) and works very fine. Except one thing, that I hoped to find in dracut but does not seem to do anything special about it. It just goes through switch-root it seems. As I understood it, systemctl switch-root will either run the specified init, or exec to the systemd in the new root. Looking a little through the code, it seems to do some kind of state-passing that I still have to study (--switched-root --deserialize etc.). Yes, we serialize the state of all units into a file, and pass its fd plus all other open fds we need need to pass over via the exec(). On the other side we deserialize the stream, and try to match the passed fds to what the serialization says. But this is mostly internal, the file is never visible in the filesystem (it is deleted right after creation), nobody should interfere with that. Problem: in NixOS we need to run a further stage in the new root, before starting systemd. For example /etc is a symlink to a configuration tree which gets created at boot (we call it activation), and so on. Our init script activates the NixOS system and ultimately exec to systemd. I'd recommend doing that in an initrd service, that you run after /sysroot is mounted, and before we actually switch roots. The serialization is only enabled if we detect that the binary we invoke is actually systemd. Because otherwise the invoked process could get seriously confused by the open fds we dump on it... initrd init - setup some env vars and mount points - systemd/initrd - switch-root - system activation script - systemd. Questions: 1) What are the advantages to let switch-root exec to systemd directly? Does executing it from our init is the same thing? Well, you get the state serialization and stuff, which means after boot-up you can investigate what happened to the initrd services and stuff... Also, you get fancy stuff like that we switch-root back into the initrd, so that the initrd can unmount the root file system before going down. 2) In case it's not the same thing, where is the best place to run that script? As a service in the new-root systemd? As a service in the initrd. Lennart -- Lennart Poettering, Red Hat ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel
Re: [systemd-devel] About systemd in initrd support
On Mon, 25.08.14 22:13, Luca Bruno (lethalma...@gmail.com) wrote: As you already mentioned, you'd have to make sure you manage to pass through the state correctly. Thanks. Is there any docs I can read about this or just read the code? It appears that systemd dumps the state into a file, and afterwards it's passed to the new systemd instance. No, it's not documented, it's an internal interface of systemd. Nobody should interfere with it... Lennart -- Lennart Poettering, Red Hat ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel
[systemd-devel] About systemd in initrd support
I'm going to do an experiment with NixOS: replace the whole current initrd process made of scripts and hooks with systemd. Before doing any work however I'd like to hear whether systemd in initrd is still wanted in the future, or there's any possible idea about dropping this support. Also, apart arch linux, is there any other OS that you know using systemd for the whole initrd process? Thanks for you work. Best regards, -- www.debian.org - The Universal Operating System ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel
Re: [systemd-devel] About systemd in initrd support
Hej, 2014-08-23 13:46 GMT+02:00 Luca Bruno lethalma...@gmail.com: I'm going to do an experiment with NixOS: replace the whole current initrd process made of scripts and hooks with systemd. Before doing any work however I'd like to hear whether systemd in initrd is still wanted in the future, or there's any possible idea about dropping this support. I think this is definitly still wanted. Also, apart arch linux, is there any other OS that you know using systemd for the whole initrd process? Every distribution that uses dracut as an initramfs, including mageia, fedora and RHEL. Thanks for you work. Best regards, Simon Peeters ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel
Re: [systemd-devel] About systemd in initrd support
On 23 August 2014 13:46, Luca Bruno lethalma...@gmail.com wrote: I'm going to do an experiment with NixOS: replace the whole current initrd process made of scripts and hooks with systemd. What a coincidence... I just switched to NixOS last week, moved some file systems around, and promptly broke my boot. Badly. The learning curve was steepened by the proprietary initrd script, which gave me exactly 0 error messages until I could find a live CD and look up the NixOS-specific boot options on-line. It also manages to boot slower than my previous systemd-based initrds. So, yes -- please. Also, apart arch linux, is there any other OS that you know using systemd for the whole initrd process? Simon's right: switching to dracut brings relatively decent systemd support more or less for free. I'd focus on that. Regarding distributions: I've been using dracut on Exherbo (A Less Brain-dead Gentoo®) for a year or so. It's the official initrd generator in that there's a blog post somewhere saying guys you really should use dracut, but there's no distribution-specific code or glue anywhere. It still works flawlessly. I take that as a heartening hint that using it under NixOS should be relatively straightforward. Regards, T G-R Thanks for you work. Best regards, -- www.debian.org - The Universal Operating System ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel
