Re: Boot hangs in single-user mode
I have tracked down the issue. Not sure whether this is a PR issue or not... On 2013-06-06, at 11:18 AM, Polytropon wrote: On Thu, 6 Jun 2013 10:24:52 -0300, Andrew Hamilton-Wright wrote: Strangely, it seems that I cannot boot single user, either using boot -s from the boot loader, or using the boot menu. When I get to the point where the root filesystem is mounted, it hangs right after printing the message: Trying to mount root from ufs:/dev/ada0s1a Have you tried hitting the RETURN key several times? [ ... ] It's important to identify if the system is _really_ hanging, or if the message just isn't visible... This is indeed the crux of the issue. While hammering on the RETURN key did not produce a prompt, it turns out that there was a prompt... At some time in the relatively distant past, I had configured this machine to allow display to a serial console (long since disconnected) by adding these lines to /boot/loader.conf boot_multicons=YES boot_serial=YES comconsole_speed=19200 console=comconsole,vidconsole My notes say These came from the serial console setup page, and do work for vt100, however I did not note exactly which man page they came from, unfortunately. I do not see these lines on syscons(4), sio(4) or dcons(4). Similar lines are mentioned in the handbook regarding setting up a serial console (there is no mention of single-user mode here): http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/serialconsole-setup.html The issue, as it relates to single-user mode, is essentially this: if the system is configured to boot with multi-console options, then when the single user prompt is printed, it is only printed on the second console (which is also the only valid source of keyboard input) -- in this case, the configured but unattached serial port. I'm not sure what the best strategy is here. Having only one console that is accepting input for the single-user shell certainly makes sense. The question is, which of potentially several consoles should it be? IMO, it would be better/clearer if (for i386/amd64 anyway) the console was the one associated with the motherboard-based keyboard and video card. An argument here would be that the [CTRL]-[ALT]-[DEL] sequence is still valid when associated with this keyboard, so it does seem odd that other input on that device is ignored. I can see arguments for other setups, also, mostly revolving around the why would you _have_ another console configured if you didn't need it, so the configured console must therefore be the important one -- though the FreeBSD user base is certainly willing enough to experiment that I am sure I am not the only person who set up multi-console for a fun project. Perhaps the best strategy would be to add a message printed on all consoles (as the rest of the boot information is) just before the prompt is printed (singly) to let people know that this is happening? I'm not sure if a way to 100% predict the desired console is possible. Thoughts? If figure I will put a PR in, so that at least this is tracked, even if we don't change anything. I will reference this thread in the PR, but if anyone has input as to what to suggest, I would appreciate it. At the very least, the handbook should get updated to indicate that this may happen. Andrew. ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to freebsd-questions-unsubscr...@freebsd.org
Re: Boot hangs in single-user mode
Hi Everyone, On Thu, 6 Jun 2013 10:24:52 -0300, Andrew Hamilton-Wright wrote: Strangely, it seems that I cannot boot single user, either using boot -s from the boot loader, or using the boot menu. When I get to the point where the root filesystem is mounted, it hangs right after printing the message: Trying to mount root from ufs:/dev/ada0s1a There was a bit of a delay getting back to this, as I needed to move the internals over to a replacement server in a planned upgrade. I have left the boot disk in the machine demonstrating this problem with the intention of coming back to determine what is going on (mount points to now-missing data disks have been removed from /etc/fstab). In the resulting stripped down system, I have the same behaviour as before -- I cannot get to single-user mode, but multi-user is fine. If in multi-user mode, if I issue kill -TERM 1 to go to single-user mode, I would get a single console message: pflog0: promiscuous mode disabled, then nothing. While I would expect pflog to shut down in this case, I have now disabled everything pf related (I cannot imagine that it would interfere with console operation), and now have the situation where kill -TERM 1 simply locks the console. Plugging in a USB device while the console is locked does produce the expected dmesg updates, and the system does respond to [CTRL]-[ALT]-[DEL] I will also add that I can boot to a single-user prompt when booting off of the 9.1 media via DVD and mounting the root filesystem from the disk. (This motherboard+kernel have never gotten along particularly well with the DVD reader/writer in the machine, so mounting the filesystem from the DVD usually fails with various atapi based timeouts). Does anyone have any thoughts on how to further explore this? As the situation was more than mildly annoying, and could certainly have been worse, if this is likely to occur for anyone else, I would like to file a PR. Thanks, Andrew. ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to freebsd-questions-unsubscr...@freebsd.org
Boot hangs in single-user mode
Strangely, it seems that I cannot boot single user, either using boot -s from the boot loader, or using the boot menu. When I get to the point where the root filesystem is mounted, it hangs right after printing the message: Trying to mount root from ufs:/dev/ada0s1a Interestingly, there seems to be a bit of a sequence issue, as I have also seen the mount message appear before the audio system comes up, so occasionally, the last item printed is: pcm0: USB audio on uaudio0 If I boot normally, however, I can consistently reach a login prompt. I suspect that this may be a race condition of some kind, as yesterday I am sure I successfully booted to single-user while trying to solve a separate problem. In case the separate problem (failed disk) is relevant, the general situation is this: - four disk machine: ada0 (/, /usr, /tmp, /var); ada1 (/research -- data only), ada2 (/home), ada3 (/data -- also data only) - the disk ada2 has failed - in preparing to replace ada2, I have commented out all references to it from /etc/fstab I am rebooting the machine at the moment as I wish to ensure that I know which physical disk is ada2, so want to boot the machine without it plugged in. I seem to have trouble booting at all with ada2 missing and ada3 still attached, but can boot to multiuser with no problems in either of these two configuration: - all disks (including the faulty one) plugged in, with ada2 references removed from /etc/fstab - ada2 and ada3 not physically plugged in, and all references to either removed from /etc/fstab Neither combination allows me to boot single-user. While I can clearly go ahead with my disk replacement, this is not only strange and annoying, but potentially problematic. Has anyone else seen anything like this? I notice that there are several messages (dating back to 2004) in the list indicating 'hang after Trying to mount root' or 'hang after sbin_init' (which is the message that will be seen when booting single-user in verbose mode). Thoughts? Ideas? Thanks, Andrew. ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to freebsd-questions-unsubscr...@freebsd.org
Re: Boot hangs in single-user mode
On Thu, 6 Jun 2013 10:24:52 -0300, Andrew Hamilton-Wright wrote: Strangely, it seems that I cannot boot single user, either using boot -s from the boot loader, or using the boot menu. When I get to the point where the root filesystem is mounted, it hangs right after printing the message: Trying to mount root from ufs:/dev/ada0s1a Have you tried hitting the RETURN key several times? I've seen what you've described once (I think on a FreeBSD 5 system): The prompt Enter full pathname of shell or RETURN for /bin/sh: _ would not appear, but the system was still responding. Hitting RETURN made that prompt visible and the SUM shell prompt was properly displayed. It's important to identify if the system is _really_ hanging, or if the message just isn't visible... Interestingly, there seems to be a bit of a sequence issue, as I have also seen the mount message appear before the audio system comes up, so occasionally, the last item printed is: pcm0: USB audio on uaudio0 This seems to indicate that the system is still responding, i. e., the kernel is up and running. Whenever new hardware is detected, the kernel will issue a console message. For example, on my home system the detection of the built-in USB is sometimes a bit slow, so its messages appear later on in the booting sequence, _after_ the initial kernel messages (e. g., during firewall initialisation). I suspect that this may be a race condition of some kind, as yesterday I am sure I successfully booted to single-user while trying to solve a separate problem. Try some more. :-) I am rebooting the machine at the moment as I wish to ensure that I know which physical disk is ada2, so want to boot the machine without it plugged in. A suggestion: I tend to keep a tendency to use labels instead of device names to identify disks. This is handy in case you're running some kind of RAID configuration or use striping and mirroring. Mark the disks with numbers and colors, as you prefer (for example this nomenclature: color = stripe, number = mirror), to reflect being element of a stripe and being one of the mirrors of N properties both by the label (software) and the physical disk (hardware). So you can _directly_ deduct from a label (for example of a disk that is reported as failing) like red 2 that the disk is the 2nd mirror disk in the red stripe, and _which_ physical disk is it? The one with a red 2 on it. :-) -- Polytropon Magdeburg, Germany Happy FreeBSD user since 4.0 Andra moi ennepe, Mousa, ... ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to freebsd-questions-unsubscr...@freebsd.org
Re: Boot hangs in single-user mode
[ Condensation of earlier comments below ] On 2013-06-06, at 11:18 AM, Polytropon wrote: On Thu, 6 Jun 2013 10:24:52 -0300, Andrew Hamilton-Wright wrote: When I get to the point where the root filesystem is mounted, it hangs right after printing the message: Trying to mount root from ufs:/dev/ada0s1a Have you tried hitting the RETURN key several times? ... It's important to identify if the system is _really_ hanging, or if the message just isn't visible... I did try that -- I have seen that behaviour before too. I tried hitting return a half-dozen times, and have additionally tried waiting (up to 20 min) to see if it would come back, to no avail. Interestingly, there seems to be a bit of a sequence issue, as I have also seen the mount message appear before the audio system comes up, so occasionally, the last item printed is: pcm0: USB audio on uaudio0 This seems to indicate that the system is still responding, i. e., the kernel is up and running. Whenever new hardware is detected, the kernel will issue a console message. That is a good point -- I will try plugging in an external USB device at this point, and see what happens then. It certainly appears that the system is generally running to me, as well. I should also mention that the system does respond nicely to [CTRL]-[ALT]-[DEL], which triggers the expected reboot process. I am rebooting the machine at the moment as I wish to ensure that I know which physical disk is ada2, so want to boot the machine without it plugged in. A suggestion: I tend to keep a tendency to use labels instead of device names to identify disks. This is handy in case you're This is an excellent idea. I do follow some variant of this (however work at a high enough level of paranoia that I want to be able to perform the did the right drive disappear when I unplugged it check just to ensure that I wasn't asleep when making up the labels. ;-) Thanks for the suggestions -- I will keep looking at it, and will try adding a USB device once this restore eventually completes. Thanks, Andrew. ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to freebsd-questions-unsubscr...@freebsd.org
