System adminsitrator Chris Siebenmann has found Modern versions of systemd can cause an unmount storm during shutdowns:
One of my discoveries about Ubuntu 20.04 is that my test machine can trigger the kernel's out of memory killing during shutdown. My test virtual machine has 4 GB of RAM and 1 GB of swap, but it also has 347 NFS[*] mounts, and after some investigation, what appears to be happening is that in the 20.04 version of systemd (systemd 245 plus whatever changes Ubuntu has made), systemd now seems to try to run umount for all of those filesystems all at once (which also starts a umount.nfs process for each one). On 20.04, this is apparently enough to OOM[**] my test machine.
[...] Unfortunately, so far I haven't found a way to control this in systemd. There appears to be no way to set limits on how many unmounts systemd will try to do at once (or in general how many units it will try to stop at once, even if that requires running programs). Nor can we readily modify the mount units, because all of our NFS mounts are done through shell scripts by directly calling
mount
; they don't exist in/etc/fstab
or as actual.mount
units.
[*] NFS: Network File System
[**] OOM Out of memory.
We've been here before and there is certainly more where that came from.
Previously:
(2020) Linux Home Directory Management is About to Undergo Major Change
(2019) System Down: A systemd-journald Exploit
(2017) Savaged by Systemd
(2017) Linux systemd Gives Root Privileges to Invalid Usernames
(2016) Systemd Crashing Bug
(2015) tmux Coders Asked to Add Special Code for systemd
(2016) SystemD Mounts EFI pseudo-fs RW, Facilitates Permanently Bricking Laptops, Closes Bug Invalid
(2015) A Technical Critique of Systemd
(2014) Devuan Developers Can Be Reached Via vua@debianfork.org
(2014) Systemd-resolved Subject to Cache Poisoning
(Score: 2) by janrinok on Tuesday May 12 2020, @06:41AM (1 child)
I know its systemd.homed - you know that from 'systemd' in the title. Homed is perfectly understandable. People use journald, systemctl , and loginctl without having to prefix them with 'systemd.' Why should homed be any different?
The day it is no longer optional is the day I will object to it. I don't object to black cars on the road, people wearing funny hats, or those that want to wear odd coloured socks. I will complain about them when they are made compulsory.
I have that version of systemd (245) on 4 of my systems but I do not use homed. It is OPTIONAL until as you say, it isn't (maybe, one day, eventually, ...) It works just like it always has done. I can ssh into my home directories without any hassle. There hasn't been an outcry when every copy of Ubuntu, Debian or Fedora users suddenly stopped working - because it hasn't happened. Like all software, you have to know how and when to use it.
(Score: 2) by DannyB on Tuesday May 12 2020, @03:46PM
I'll bet you don't write GNU/Linux either.
(nor do I)
To transfer files: right-click on file, pick Copy. Unplug mouse, plug mouse into other computer. Right-click, paste.