Comments on: Introduction to Linux Signals 101 http://taz.net.au/blog/2008/07/03/introduction-to-linux-signals-101/ Tech Notes And Miscellaneous Thoughts Sat, 07 Mar 2009 08:48:01 +0000 hourly 1 http://wordpress.org/?v=3.0 By: TimC http://taz.net.au/blog/2008/07/03/introduction-to-linux-signals-101/comment-page-1/#comment-51 TimC Thu, 03 Jul 2008 21:48:48 +0000 http://taz.net.au/blog/?p=14#comment-51 Nope. The bug report about mount was the reason for me being in emergency mode (turns out you can't remount / rw if there's a syntax error with the / entry in /etc/fstab, and you can't tell mount to ignore /etc/fstab). ctrl-c wasn't sufficient to tell bash to cancel a line. Eg, go to bash shell, type "askjhaksjdhkj", press ctrl-C, that should clear the line. No acknowledgement at all in my case. Nope. The bug report about mount was the reason for me being in emergency mode (turns out you can’t remount / rw if there’s a syntax error with the / entry in /etc/fstab, and you can’t tell mount to ignore /etc/fstab).

ctrl-c wasn’t sufficient to tell bash to cancel a line. Eg, go to bash shell, type “askjhaksjdhkj”, press ctrl-C, that should clear the line. No acknowledgement at all in my case.

]]> By: cas http://taz.net.au/blog/2008/07/03/introduction-to-linux-signals-101/comment-page-1/#comment-50 cas Thu, 03 Jul 2008 21:23:00 +0000 http://taz.net.au/blog/?p=14#comment-50 i'm guessing that mount(8) called the kernel to actually mount a filesystem, or perhaps query the kernel for a list of mounted filesystems....and the syscall never returned, perhaps because of hardware errors on the disk or disk controller. SIGINT won't kill a process if it's trapped in the kernel. it won't even get the signal until the syscall returns. even SIGKILL ('kill -9') won't kill a zombie process. i’m guessing that mount(8) called the kernel to actually mount a filesystem, or perhaps query the kernel for a list of mounted filesystems….and the syscall never returned, perhaps because of hardware errors on the disk or disk controller.

SIGINT won’t kill a process if it’s trapped in the kernel. it won’t even get the signal until the syscall returns.

even SIGKILL (‘kill -9′) won’t kill a zombie process.

]]> By: TimC http://taz.net.au/blog/2008/07/03/introduction-to-linux-signals-101/comment-page-1/#comment-48 TimC Thu, 03 Jul 2008 11:37:23 +0000 http://taz.net.au/blog/?p=14#comment-48 Turns out I had reason to go into such an emergency mode tonight (I'm about to submit a bug report to mount -- grarrr). And an stty sane didn't work. stty -a showed that ^C was indeed mapped to intr. Turns out I had reason to go into such an emergency mode tonight (I’m about to submit a bug report to mount — grarrr). And an stty sane didn’t work. stty -a showed that ^C was indeed mapped to intr.

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