When is it absolutely necessary to reboot a *NIX box?

[Heisenberg]

I was thinking the other day and wondering about this. It seems to me the only time you absolutely have to reboot a *NIX machine is when kernel changes are made. Every thing else can be updated/patched and services/daemons then restarted without restarting the machine. Comments/ideas?

 

[JavaMomma]

how about the ol reboot to Windows to play games?

 

[Sunner]

I read somewhere that Sun(or was it HPaq...?) is working on "hotswitching" of kernels as well.
With the proper hardware, such as Sun's SunFire 3800 or better, where you can hotswap all the hardware on the run, that would pretty much make the reboot command obsolete

 

[TheOmegaCode]

Originally posted by: Sunner
I read somewhere that Sun(or was it HPaq...?) is working on "hotswitching" of kernels as well.
With the proper hardware, such as Sun's SunFire 3800 or better, where you can hotswap all the hardware on the run, that would pretty much make the reboot command obsolete

Aren't new Linux kernels are working on hot swappable cpu's?

 

[ProviaFan]

Originally posted by: TheOmegaCode

Originally posted by: Sunner
I read somewhere that Sun(or was it HPaq...?) is working on "hotswitching" of kernels as well.
With the proper hardware, such as Sun's SunFire 3800 or better, where you can hotswap all the hardware on the run, that would pretty much make the reboot command obsolete

Aren't new Linux kernels are working on hot swappable cpu's?

I can't see how hotswap CPUs would work, unless you're talking about adding or removing CPU nodes (or "bricks") on high end servers while they're up.

 

[Sunner]

Well, in a Sunfire you don't just yank the CPU out, you shutdown and pull an entire system board, which includes CPU(s) and memory.
Then you just change it's configuration, say add another gig of RAM, put it back in, and activate it.

In short that is

As for Linux and hotswap CPU's, didn't Linus say something about this in the recent 2.5 kernel summary?

 

[n0cmonkey]

Originally posted by: Sunner
I read somewhere that Sun(or was it HPaq...?) is working on "hotswitching" of kernels as well.
With the proper hardware, such as Sun's SunFire 3800 or better, where you can hotswap all the hardware on the run, that would pretty much make the reboot command obsolete

Ive heard about things like this too. It wold be quite neat. Embedded XP supposedly has something almost as nice. Supposedly it runs two of itself or something... Cant remember all of the details.

When do I reboot? When I change something in the kernel, apply deep patches (libraries), or when I apply a lot of patches and I just want to make sure everything running is patched without having to go through everything and possibly missing one or two things.

 

[CTho9305]

Originally posted by: n0cmonkey

Originally posted by: Sunner
I read somewhere that Sun(or was it HPaq...?) is working on "hotswitching" of kernels as well.
With the proper hardware, such as Sun's SunFire 3800 or better, where you can hotswap all the hardware on the run, that would pretty much make the reboot command obsolete

Ive heard about things like this too. It wold be quite neat. Embedded XP supposedly has something almost as nice. Supposedly it runs two of itself or something... Cant remember all of the details.

When do I reboot? When I change something in the kernel, apply deep patches (libraries), or when I apply a lot of patches and I just want to make sure everything running is patched without having to go through everything and possibly missing one or two things.

you dont just drop to init 0?

 

[n0cmonkey]

Originally posted by: CTho9305

Originally posted by: n0cmonkey

Originally posted by: Sunner
I read somewhere that Sun(or was it HPaq...?) is working on "hotswitching" of kernels as well.
With the proper hardware, such as Sun's SunFire 3800 or better, where you can hotswap all the hardware on the run, that would pretty much make the reboot command obsolete

Ive heard about things like this too. It wold be quite neat. Embedded XP supposedly has something almost as nice. Supposedly it runs two of itself or something... Cant remember all of the details.

When do I reboot? When I change something in the kernel, apply deep patches (libraries), or when I apply a lot of patches and I just want to make sure everything running is patched without having to go through everything and possibly missing one or two things.

you dont just drop to init 0?

Why would I? To keep some stupid uptime record? I can modify my uptime, I dont need to keep myself from rebooting

 

[CTho9305]

Originally posted by: n0cmonkey

Originally posted by: CTho9305

Originally posted by: n0cmonkey

Originally posted by: Sunner
I read somewhere that Sun(or was it HPaq...?) is working on "hotswitching" of kernels as well.
With the proper hardware, such as Sun's SunFire 3800 or better, where you can hotswap all the hardware on the run, that would pretty much make the reboot command obsolete

Ive heard about things like this too. It wold be quite neat. Embedded XP supposedly has something almost as nice. Supposedly it runs two of itself or something... Cant remember all of the details.

When do I reboot? When I change something in the kernel, apply deep patches (libraries), or when I apply a lot of patches and I just want to make sure everything running is patched without having to go through everything and possibly missing one or two things.

you dont just drop to init 0?

Why would I? To keep some stupid uptime record? I can modify my uptime, I dont need to keep myself from rebooting

cheating is for losers
straight dump of /proc/uptime or whatever that is (running redhat 5.2). I dont know how to interpret those - my C program (the .out) just divides one of the by # of seconds in a day and reports it.

 

[Buddha Bart]

Personally, I reboot almost every time I made a config change. You never wanna be in the place where when troubleshooting something you hand-wrote an extra iptables rule, but never remembered to put it in your firewall script. Or hand-started a daemon, but forgot to add it to your init scripts. 8 months later you'll actually have to reboot because of some real issue, and suddenly you'll have to re-solve all your old problems. Yes this is a sloppy mistake, but as long as you suffer from the same 23 pairs of chromosomes as the rest of us you are likely to make it no matter how hardcore you think you are.

Besides, there's really only three types of systems.

1.) simple home/office user: uptime doesnt matter, just reboot.
2.) production server: load balanced or configured with failover, one node can be down for 2 minutes to reboot without a problem.
3.) rediculously high-end machines: all aspects of a change are made in test environments, then moved over.

Linux/Unix's ability to make more changes than say windows without requiring a reboot has no real business value. Any server who's uptime is too important for a 5 minute reboot, belongs in at least a failover-cluster.

bart

 

[Nothinman]

The only times a reboot are needed are when:

A kernel change is needed, meaning someting you can't load as a module or a parameter you can't do at runtime via /proc (like mem= or profile=).
Hardware problem, I've had times when IDE devices get whacked out and need a power cycle to reset.
Sanity check, you made some config changes and you want to make sure everything comes up clean

You only need to restart apps when you update libs they're dependent on, hell I've updated X while it's running left it running only to notice it was updated when I started an OpenGL app and realized the normal mesa OpenGL libs replaced the nVidia ones.

I can't see how hotswap CPUs would work, unless you're talking about adding or removing CPU nodes (or "bricks") on high end servers while they're up.

No you can't remove CPUs on normal hardware, but you can on very high-end hardware and Linux can handle this now. You tell the OS to stop using CPU X then you do whatever's necesary in the hardware to remove it. I think you can tell Linux to stop using CPU X in a 'normal' SMP config just to see it partially work if you're interested, although I havn't tried it.

I think once 2.6 finalizes pretty much everything will be hot-swappable as long as the hardware supports it.