Re: [systemd-devel] The first and the last things in systemd's lifecycle
On Di, 14.05.19 09:23, Ulrich Windl (ulrich.wi...@rz.uni-regensburg.de) wrote: > > /var/run needs /var which is not guaranteed to be there when you need > > it which complicates things. > > Thanks, > > I'll start a new thread on this (I wanted to ask anyway): > AFAIK systemd does socket communication a lot, while old init was > happy with just a root filesystem. sysvinit communicated via a fifo in the file system. This isn't too different, except maybe it's one way and single-connection while sockets are duplex and can have parallel connections generally. > So I wonder how this Hen-Egg_Problem is solved: Systemd needs a > socket to operate, but to provide the infrastructure, systemd would > need the socket do do so. Or expressed in other words: How can > systemd create /run when it needs /run to operate? systemd mounts /run early on if its not mounted yet, becore creating any sockets in it. > The corresponding question would be for shutdown: How will systemd > unmount /run? OK, if ist a ramdisk, it's not really needed. It closes all sockets, then unmounts it. /run has to be a tmpfs, so yes, it's backed by pageable memory. > Another related question is that of shutdown in general: > > For startup the semantics of Before= and After= are clear, but isn't > it just reverted for shutdown? That is if "M" has "After=X" and > "Before=Y", does that imply that Y is stopped before M will be > stzopped, and M will be stopped before X is? Yes, the order between two ordered units is reversed if both are stopped. THat's how that is implemented. Lennart -- Lennart Poettering, Berlin ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/systemd-devel
Re: [systemd-devel] The first and the last things in systemd's lifecycle
On Tue, May 14, 2019 at 10:24 AM Ulrich Windl < ulrich.wi...@rz.uni-regensburg.de> wrote: > >>> Andrei Borzenkov schrieb am 14.05.2019 um 08:40 > in > Nachricht > : > > On Tue, May 14, 2019 at 9:35 AM Ulrich Windl > > wrote: > > > >> > >> I knew that. It doesn't answer _why_ /var/run is obsolete. > >> > > > > /var/run needs /var which is not guaranteed to be there when you need > > it which complicates things. > > Thanks, > > I'll start a new thread on this (I wanted to ask anyway): > AFAIK systemd does socket communication a lot, while old init was happy > with just a root filesystem. > So I wonder how this Hen-Egg_Problem is solved: Systemd needs a socket to > operate, but to provide the infrastructure, systemd would need the socket > do do so. > Or expressed in other words: How can systemd create /run when it needs > /run to operate? > 1. systemd performs these actions during initialization, before switching to the main loop. 2. systemd can operate without any sockets; it connects to D-Bus for control once it becomes available, but it's not a runtime requirement. > The corresponding question would be for shutdown: How will systemd unmount > /run? OK, if ist a ramdisk, it's not really needed. > The 'systemd-shutdown' binary doesn't unmount /run or /, it keeps the former and remounts the latter read-only. (It can optionally pivot_root *to* /run, though, and unmount / using the "shutdown initramfs" feature.) > > Another related question is that of shutdown in general: > For startup the semantics of Before= and After= are clear, but isn't it > just reverted for shutdown? That is if "M" has "After=X" and "Before=Y", > does that imply that Y is stopped before M will be stzopped, and M will be > stopped before X is? > Yes, it is reversed on shutdown. > > From the experience how fast shutdown happens, I don't think it's like > that. > Usually killing processes is faster than loading them from disk. -- Mantas Mikulėnas ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/systemd-devel
[systemd-devel] The first and the last things in systemd's lifecycle
>>> Andrei Borzenkov schrieb am 14.05.2019 um 08:40 in Nachricht : > On Tue, May 14, 2019 at 9:35 AM Ulrich Windl > wrote: > >> >> I knew that. It doesn't answer _why_ /var/run is obsolete. >> > > /var/run needs /var which is not guaranteed to be there when you need > it which complicates things. Thanks, I'll start a new thread on this (I wanted to ask anyway): AFAIK systemd does socket communication a lot, while old init was happy with just a root filesystem. So I wonder how this Hen-Egg_Problem is solved: Systemd needs a socket to operate, but to provide the infrastructure, systemd would need the socket do do so. Or expressed in other words: How can systemd create /run when it needs /run to operate? The corresponding question would be for shutdown: How will systemd unmount /run? OK, if ist a ramdisk, it's not really needed. Another related question is that of shutdown in general: For startup the semantics of Before= and After= are clear, but isn't it just reverted for shutdown? That is if "M" has "After=X" and "Before=Y", does that imply that Y is stopped before M will be stzopped, and M will be stopped before X is? From the experience how fast shutdown happens, I don't think it's like that. Regards, Ulrich ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/systemd-devel
