Bookworm update behavior

The update process will usually restart server processes immediately, although AFAIK this is something each package has to do at least somewhat independently, so presumably mistakes can happen.

Apart from that, once an update completes, new executables (and libraries etc) are available to run immediately, but they will only start running next time something executes them. For example if you update Bash, existing logins will be unchanged but new logins will get the updated shell.

There’s no time-based delay.

I think that’s basically right. An update to init (usually meaning systemd now) may require a reboot before it takes fully (not sure), but apart from that there’s very little that inherently needs a reboot.

In general you dont need to reboot, but you may need to restart some applications Firefox doesn't upgrade in place nicely, for example...

Almost. But there is at least one core library, the C runtime, that is linked into just about every process that runs. So an update to that library requires those processes to restart.

It’s likely those service restarts happened without you noticing.

Greg Kroah-Hartman, “Mr Linux Device Drivers”, has said

The Pixel desktop updater works in the background downloading and applying the changes. Unless you have not done an update many months it should only take a couple of minutes, except if your WiFi is exceptionally slow.

Your comment about WiFi stopping working does sound like either poor signal strength or a hardware unreliability, updates would be extraordinarily unlikely to affect WiFi.

Youtube is a very highly CPU intensive task even on the fastest Pi 5, so I would suspect something wrong such as slow WiFi, lack of free memory or CPU throttling causing issues rather than any update.

Raspberry Pi OS kernels only tend to be released a couple of times a year, so only very rarely will a reboot be required after an upgrade.

Even then it's optional, but as I do daily backups I prefer to reboot to check the system works before the new files make it in to the backup that night - as if I needed to wind back then I'd have to go to an archived weekly or monthly backup copy.

---druck

It doesn't require them to restart, but things that can restart without user intervention such as services are usually set to do so. Applications in use generally don't insist on restarting, with the notable exception of Firefox.

The update process will delete the old executables and shared libraries and replace them with updated copies which are used when programs are next run. Anything already running will cause the deleted files to still exist unlinked on the storage until they are closed and the space given back to the system.

---druck

You don’t get the effect of the update until they do. Just as you don’t get the effect of the new kernel until it, too, (re)boots.

As a rule, the system(s) report "system is up to date" within a few minutes. One of them is a Pi5 with wired ethernet. the other is a Pi2 on WiFi.

How long might it take for services to restart after that point on the machine with wired ethernet?

Thanks for writing,

bob prohaska

They are restarted during the upgrade. If you are getting “system is up to date” then the process has finished.

They restart as the update is taking place.

Instead of using the desktop installer, next time pop up a terminal and do a:-

sudo apt update sudo apt full-upgrade -y

You'll then see all the information on what is doing going by, and when you get the prompt back it is all done.

But as I said, something else is going wrong on your system. Is it chronically short of memory? If so just doing an update could cause something to be booted out of memory sometime later.

If you have that terminal still open do a:-

free -h

---druck

The Pi5 reports total used free shared buff/cache available Mem: 7.9Gi 2.3Gi 2.0Gi 537Mi 4.2Gi 5.6Gi Swap: 199Mi 150Mi 49Mi

The Pi2 of course much less, around 500M available. Clearly it's both memory and CPU bound. My grumbles were mostly directed at the Pi5, very hard to see how it could have memory limitations.

Thanks for writing,

bob prohaska .