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#1 2005-04-30 13:46:03

Michel
Member
From: Belgium
Registered: 2004-07-31
Posts: 286

upgrading critical packages like the kernel-package

Heya,

I was just thinking of the following situation, especially the kernel:

You have 1 kernel installed and there is an update for the kernel. I believe pacman upgrades a package by first deleting it and then installiung it ? Say the kernel is being upgraded. Pacman deleted the kernel package or critical files of it. Computer crashes ... you have to reboot. You can't reboot quickly because there is no more kernel image for example.


Ofcourse, if you have physical access to the computer you can use an rescue-cd or so to mount the filesystem and use pacman to install the package from the local package-cache using the root-parameter or so, but it would be better if the above "problematic" situation couldn't occur I suppose.

I recently encountered libjio for transactioned i/O. I haven't used it, but maybe it is interesting to have a look at.

Michel

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#2 2005-04-30 14:29:48

Michel
Member
From: Belgium
Registered: 2004-07-31
Posts: 286

Re: upgrading critical packages like the kernel-package

Heya,

it seems libjio provides transactional support for reading and writing to a file, but not removing, ... files it seems. Ofcourse you can create a log this way, but maybe this is overhead.

Michel

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#3 2005-04-30 15:59:04

phrakture
Arch Overlord
From: behind you
Registered: 2003-10-29
Posts: 7,879
Website

Re: upgrading critical packages like the kernel-package

Michel wrote:

You have 1 kernel installed and there is an update for the kernel. I believe pacman upgrades a package by first deleting it and then installiung it ? Say the kernel is being upgraded. Pacman deleted the kernel package or critical files of it. Computer crashes ... you have to reboot. You can't reboot quickly because there is no more kernel image for example.

It shouldn't work like this - a running image will remain running.  When I upgrade my kernel, sometimes I remain running for a few days before I reboot... it never crashes..

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#4 2005-04-30 17:13:37

Moo-Crumpus
Member
From: Hessen / Germany
Registered: 2003-12-01
Posts: 1,443

Re: upgrading critical packages like the kernel-package

Why don't you store a kernel set as fallback opportunity?
Copy kernel26 etc. to kernel26-sic, and add an entry to grub. Sometimes, it takes a man smile


Frumpus addict
[mu'.krum.pus], [frum.pus]

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#5 2005-04-30 22:33:43

Michel
Member
From: Belgium
Registered: 2004-07-31
Posts: 286

Re: upgrading critical packages like the kernel-package

Heya,

I'm not saying it is likely to happen or that there isn't a way to solve it like having a second boot-option. I'm just arguing that if it could be avoided it may be better to avoid it from happening.

Michel

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#6 2005-05-01 00:57:41

T-Dawg
Forum Fellow
From: Wilmington, NC
Registered: 2005-01-29
Posts: 2,734

Re: upgrading critical packages like the kernel-package

Everything the kernel needs to run the system is stored in ram. Unless your doing alot of strange and demanding tasks, I wouldn't worry about it.

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#7 2005-05-01 01:00:30

phrakture
Arch Overlord
From: behind you
Registered: 2003-10-29
Posts: 7,879
Website

Re: upgrading critical packages like the kernel-package

Michel wrote:

Heya,

I'm not saying it is likely to happen or that there isn't a way to solve it like having a second boot-option. I'm just arguing that if it could be avoided it may be better to avoid it from happening.

Michel

but it *won't* happen - I can boot up and format my entire harddrive and everything will keep running fine (well, until it needs to acess a file)

I can boot, and delete /lib/modules and /boot entirely and it'll be just as stable as if those files were there... yeah you won't have any extra modules to load, but those loaded will stay loaded...

there is no possibility of a catastrophic failure due to deletion ofthe kernel

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#8 2005-05-01 04:55:20

god
Member
Registered: 2004-12-01
Posts: 25

Re: upgrading critical packages like the kernel-package

I think you guys have missed his point. He isn't saying that the deletion of the kernel will cause the crash. He's saying that, if the computer crashes due to some other reason whilst the kernel is being installed (I know, a rarity), the potential for a minor tragedy is there. Especially if you don't have physical access to the box.

Sure, you could use a livecd and then copy a kernel over. That wouldn't be a problem unless you're an internet away.

Anyhow, I just wanted to clarify, since I think he does have a valid point.

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#9 2005-05-01 07:41:32

iphitus
Forum Fellow
From: Melbourne, Australia
Registered: 2004-10-09
Posts: 4,927

Re: upgrading critical packages like the kernel-package

god wrote:

I think you guys have missed his point. He isn't saying that the deletion of the kernel will cause the crash. He's saying that, if the computer crashes due to some other reason whilst the kernel is being installed (I know, a rarity), the potential for a minor tragedy is there. Especially if you don't have physical access to the box.

Sure, you could use a livecd and then copy a kernel over. That wouldn't be a problem unless you're an internet away.

Anyhow, I just wanted to clarify, since I think he does have a valid point.

Not really, his worry, from what i see, is paranoia.

The chances of your system crashing, within the small time frame, the matter of seconds that your new kernel is installed...... are absolutely minute.

And it would take an awesome crash to take it down, a total kernel panic/oops.. And this crash would need to happen within the few spare seconds while the kernel is installing.

If SSH or X crashed (ive never heard of that happening), that wouldnt be a problem, the system would still be running, so just wait for SSH to be re-started or login via a ctrl-alt-Fx.

And even if it did, if you use LILO, your system would still boot, as LILO embeds the kernel into the bootsector.

And either way, if you have physical access you could always pop in a   

So we're lookin at a complete kernel oops/panic, within the space of approximately a certain 5 or so seconds on a GRUB based system where you do not have physical access to the box.

It's worrying about something that isnt going to happen. And if it does, you're the most unlucky person about.

iphitus

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#10 2005-05-01 17:00:33

phrakture
Arch Overlord
From: behind you
Registered: 2003-10-29
Posts: 7,879
Website

Re: upgrading critical packages like the kernel-package

/me cheers for iphitus

well said

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#11 2005-05-01 17:39:16

i3839
Member
Registered: 2004-02-04
Posts: 1,185

Re: upgrading critical packages like the kernel-package

I always keep a backup of a working kernel in case the new one doesn't work, no matter why not. But for the slight chance that something goes wrong while upgrading the kernel? Nah...

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