feature request: fallback boot image
Hi, it would be great to be able to specify a fallback kernel in case booting a new kernel fails - esp. if one needs to work on a remote site w/o hands-on support. TIA! Kind regards, --Toni++
Re: feature request: fallback boot image
Toni Mueller wrote: Hi, it would be great to be able to specify a fallback kernel in case booting a new kernel fails - esp. if one needs to work on a remote site w/o hands-on support. TIA! Kind regards, --Toni++ If you are talking about a new install over an old one and get an ERR M, then no kernels are accessible. Different type of fix. If you are talking about an upgrade then cp bsd bsd.backup before install should do it. Then use boot boot /bsd.backup after a failed upgrade. If you are using altroot, then you already have an old copy of / anyway. -- A human being should be able to change a diaper, plan an invasion, butcher a hog, conn a ship, design a building, write a sonnet, balance accounts, build a wall, set a bone, comfort the dying, take orders, give orders, cooperate, act alone, solve equations, analyze a new problem, pitch manure, program a computer, cook a tasty meal, fight efficiently, die gallantly. Specialization is for insects. -- Robert Heinlein
Re: feature request: fallback boot image
Hi, On Fri, 02.04.2010 at 06:50:00 -0500, Chris Bennett ch...@bennettconstruction.biz wrote: If you are talking about an upgrade then cp bsd bsd.backup before install should do it. Then use boot boot /bsd.backup after a failed upgrade. I thought about the case where the new kernel won't boot and I don't have a console and power switch to reboot the machine and/or select a different kernel. It would be nice if I could say something like (in grub) fallback /bsd.backup. As I said, this is only relevant if I'm working remotely. Kind regards, --Toni++
Re: feature request: fallback boot image
Toni Mueller wrote: Hi, On Fri, 02.04.2010 at 06:50:00 -0500, Chris Bennett ch...@bennettconstruction.biz wrote: If you are talking about an upgrade then cp bsd bsd.backup before install should do it. Then use boot boot /bsd.backup after a failed upgrade. I thought about the case where the new kernel won't boot and I don't have a console and power switch to reboot the machine and/or select a different kernel. It would be nice if I could say something like (in grub) fallback /bsd.backup. As I said, this is only relevant if I'm working remotely. Kind regards, --Toni++ If you don't have access to a console remotely, then exactly how would you type fallback /bsd.backup? I haven't used GRUB myself. Does it support remote access? I occasionally use GAG, but that is very small and written in assembly. Perhaps you should get an ISP with technicians or remote IP-KVM access. I have had problems with new installs and IP-KVM just makes it vaguely annoying. My ISP also has remote access power switches. Someone else may know of a better solution that will reboot a machine that fails to boot. -- A human being should be able to change a diaper, plan an invasion, butcher a hog, conn a ship, design a building, write a sonnet, balance accounts, build a wall, set a bone, comfort the dying, take orders, give orders, cooperate, act alone, solve equations, analyze a new problem, pitch manure, program a computer, cook a tasty meal, fight efficiently, die gallantly. Specialization is for insects. -- Robert Heinlein
Re: feature request: fallback boot image
On Fri, Apr 02, 2010 at 03:21:30PM +0200, Toni Mueller wrote: | Hi, | | On Fri, 02.04.2010 at 06:50:00 -0500, Chris Bennett ch...@bennettconstruction.biz wrote: | If you are talking about an upgrade then | cp bsd bsd.backup before install should do it. | Then use boot boot /bsd.backup after a failed upgrade. | | I thought about the case where the new kernel won't boot and I don't | have a console and power switch to reboot the machine and/or select a | different kernel. It would be nice if I could say something like (in | grub) fallback /bsd.backup. | | As I said, this is only relevant if I'm working remotely. What do you mean the new kernel won't boot ? If the kernel image is there, it will be loaded by the bootloader. If it's garbage, then that's what you get: garbage. If the kernel is not there, the bootloader will automagically try /bsd. So if you have 'set image mybsd' in your /etc/boot.conf (which is frowned upon, mind you; certain things assume that your kernel is always /bsd) and /mybsd is not found, the bootloader will boot /bsd next. If that's not found either, the bootloader will cancel the timeout and wait for your input on the console. I'm thinking your talking about the first case, your new kernel won't boot means that the kernel image (/bsd) exists but it panics / crashes / calls your mom / does other fun stuff. How would the fallback solution work ? I can only think of a solution where the bootloader and userland interact somehow. The bootloader sets a flag on the kernel it tries to boot which is cleared by userland after a succesful boot. If the bootloader starts again and sees the flag set, it knows the previous boot failed and the fallback kernel should be loaded. May seem like a nice idea at first, but it doesn't sound very portable to me. The boot.conf stuff is platform specific - a workaround for broken bioses. sparc64 machines, for example, just read the kernel image name from their boot configuration and load that, no boot.conf needed at all. Cheers, Paul 'WEiRD' de Weerd -- [++-]+++.+++[---].+++[+ +++-].++[-]+.--.[-] http://www.weirdnet.nl/
Re: feature request: fallback boot image
On Fri, 02.04.2010 at 08:44:56 -0500, Chris Bennett ch...@bennettconstruction.biz wrote: If you don't have access to a console remotely, then exactly how would you type fallback /bsd.backup? I would like to see a configuration option in /etc/boot.conf that I could use to specify a fallback kernel before I reboot to a new kernel. As said, eg. Grub supports such a mechanism, although I don't know for sure how powerful it really is. I haven't used GRUB myself. Does it support remote access? Afaik, yes, but that's not the point. According to the documentation, grub detects if a kernel does not boot correctly, and then proceeds to automatically boot up to two different kernels after resetting the machine (ie, finally fails after three unsuccessful attempts). Perhaps you should get an ISP with technicians or remote IP-KVM access. Remote does not have to mean ISP or Hosting, it could also mean some remote site where you do something which requires a computer, but has nothing to do with Internet. Eg. I once saw a company that produces remote sensoring and data acquisition equipment and collects data over the Internet. These machines need to be serviced remotely, too, and in that case, often no personell whatsoever was within reach of at least a day of travelling of the affected sites. Kind regards, --Toni++
Re: feature request: fallback boot image
Hi, On Fri, 02.04.2010 at 15:50:36 +0200, Paul de Weerd we...@weirdnet.nl wrote: What do you mean the new kernel won't boot ? I mean that, for whatever reason, the kernel does not reach full multi-user capabilities within some timeout (say, 5 minutes). there, the bootloader will automagically try /bsd. So if you have 'set image mybsd' in your /etc/boot.conf (which is frowned upon, mind you; certain things assume that your kernel is always /bsd) and /mybsd is A _bad_ assumption, imho, but see below. I'll probably try to figure out why this is deemed to be a good idea. No need to repeat last year's discussion about it, which I didn't follow close enough to fully understand the issue. May seem like a nice idea at first, but it doesn't sound very portable to me. Ok... then I should probably try to figure out how to boot OpenBSD by non-BSD-supplied boot loaders (eg. grub). The boot.conf stuff is platform specific - a workaround for broken bioses. sparc64 machines, for example, just read the kernel image name from their boot configuration and load that, no boot.conf needed at all. Understood. Thanks for the summary. Kind regards, --Toni++
Re: feature request: fallback boot image
On Fri, Apr 02, 2010 at 04:50:32PM +0200, Toni Mueller wrote: | Hi, | | On Fri, 02.04.2010 at 15:50:36 +0200, Paul de Weerd we...@weirdnet.nl wrote: | What do you mean the new kernel won't boot ? | | I mean that, for whatever reason, the kernel does not reach full | multi-user capabilities within some timeout (say, 5 minutes). Your timeout idea is interesting. The bootloader loads the kernel image and then starts executing it. After this, the bootloader is no longer active, who will do this timing out ? The kernel (or the garbage that was loaded in its place) is the only code running at this point. | May seem like a nice idea at first, but it doesn't sound very portable | to me. | | Ok... then I should probably try to figure out how to boot OpenBSD by | non-BSD-supplied boot loaders (eg. grub). I don't think they will offer you the option of timing out the kernel booting. Now you may of course be doing the time out yourself (looking at your watch and pinging the remote host). In this case, clearing a flag from userland like I suggested in my previous mail becomes possible. But consider this .. after your proposed 5 minutes (or whatever time you deem sufficient) you decide something is wonky and do a remote power reset. What if it was a typo in your /etc/hostname.if or /etc/pf.conf ? The system was multiuser (the proper flags were cleared from userland) and waiting for you to log in, but you couldn't reach it... You seem to have a valid issue, but a proper solution does not appear to be obvious to me. I take it you don't have two machines under your control in these remote locations so you could exchange serial console between the two ? (a USB to serial adapter on one machine connected to the serial port of the other and vice versa) Cheers, Paul 'WEiRD' de Weerd -- [++-]+++.+++[---].+++[+ +++-].++[-]+.--.[-] http://www.weirdnet.nl/
Re: feature request: fallback boot image
On Fri, 02 Apr 2010 17:08 +0200, Paul de Weerd we...@weirdnet.nl wrote: Your timeout idea is interesting. The bootloader loads the kernel image and then starts executing it. After this, the bootloader is no longer active, who will do this timing out ? The kernel (or the garbage that was loaded in its place) is the only code running at this point. Probably naive of me to think that the bootloader could get some sort of return code (0 = OK). Maybe it's too late for it to do anything at that point. I don't know the process well enough to talk intelligently about it, just curious. snip You seem to have a valid issue, but a proper solution does not appear to be obvious to me. I take it you don't have two machines under your control in these remote locations so you could exchange serial console between the two ? (a USB to serial adapter on one machine connected to the serial port of the other and vice versa) I've done this a lot. Usually it works very well. Old, low-power hardware can be used that no longer has mush purpose. Brad
Re: feature request: fallback boot image
* Toni Mueller openbsd-m...@oeko.net [2010-04-02 12:25]: it would be great to be able to specify a fallback kernel in case booting a new kernel fails how exactly does the bootloader notice your new kernel sitting in ddb? -- Henning Brauer, h...@bsws.de, henn...@openbsd.org BS Web Services, http://bsws.de Full-Service ISP - Secure Hosting, Mail and DNS Services Dedicated Servers, Rootservers, Application Hosting
Re: feature request: fallback boot image
On Fri, 02.04.2010 at 22:20:46 +0200, Henning Brauer lists-open...@bsws.de wrote: * Toni Mueller openbsd-m...@oeko.net [2010-04-02 12:25]: it would be great to be able to specify a fallback kernel in case booting a new kernel fails how exactly does the bootloader notice your new kernel sitting in ddb? Good question. I'm not familiar with the boot process, but would assume that the boot loader could set up a timer that triggers an interrupt if not cleared after some time. The interrupt handler, installed by the boot loader, would do something that the boot loader recognizes to select a different kernel at the next reboot. In PCs, there's afaik a mandatory BIOS routine that can be used to issue a warm boot that would preserve some parts of memory. The kernel would clear the timer or diverting the interrupt handler after booting successfully, or if the user asked for entering ddb. -- Kind regards, --Toni++
Re: feature request: fallback boot image
On Fri, 02.04.2010 at 22:20:46 +0200, Henning Brauer lists-open...@bsws.de wrote: * Toni Mueller openbsd-m...@oeko.net [2010-04-02 12:25]: it would be great to be able to specify a fallback kernel in case booting a new kernel fails how exactly does the bootloader notice your new kernel sitting in ddb? Good question. I'm not familiar with the boot process, but would assume And with that last word, we're done.
