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What is a watchdog timer panic or error message?
A watchdog timer is a piece of code (or external hardware) that attempts to keep some other piece of code (or hardware) from getting stuck in an endless loop. The thing being watched is critical and nobody can imagine why it would have stopped unless all hell has broken loose somewhere
| Title | Date | Comments | |||
|---|---|---|---|---|---|
| Tuning Mac OS X for FIOS | 2011 05 | ||||
| - Tuning for broadband isn't as easy as you might think. Your usage matters and it matters a lot. - | |||||
| Controlling core files (Linux) | 2005 03 | 2011/11/06 TonyLawrence | |||
| - Control Linux core files with ulimit and /proc templates. - | |||||
| Rebuilding failed Linux software RAID | 2004 10 | 2011/10/26 kuntergunt | |||
| - Rebuild crashed Linux raid. Recently I had a hard drive fail. It was part of a Linux software RAID 1 (mirrored drives), so we lost no data, and just needed to replace hardware. However, the raid does requires rebuilding. A hardware array would usually automatically rebuild upon drive replacement, but this needed some help. - | |||||
| Numeric Unix Error Messages | 2001 12 | 2010/04/06 TonyLawrence | |||
| - It's an unfortunate fact that many programmers are lazy about error messages. Very often, all you get is a cryptic "Error 5", and you may be lucky to get that. - | |||||
| Automating Program Startup | 2000 03 | ||||
| - automating program startup methods. When you need something to start automatically, there are several ways to do it. Which one you use depends on your specific needs. - | |||||
| What is a zombie process? | 1997-2003 | 2011/11/15 TonyLawrence | |||
| - Why can't you kill a zombie process? One of the early things people learn about Unix is that a "kill -9" is invincible- that a process must die if you send it a KILL (-9). However, that's not entirely true - | |||||
| Operating System Concepts | 2003 05 | ||||
| - Basic OS concepts. The CPU (Central Processing Unit) is the heart of any computer, but the operating system is the brain. Unfortunately, understanding exactly how these things really work can be difficult, because it's fairly hard to "play" with the operating system that you are actually using. You can do quite a bit with sophisticated debuggers, but eventually you run into confusion and difficulty. And, as you try more complex tasks, you run the risk of interfering with the real machine's operating system. Finally, modern CPU's are very complex, and that complexity can make it more difficult to understand basic concepts. - | |||||
| uname version -->Re UNIX version check command | 1997-2004 | ||||
| - Usually some variant of uname, often 'uname -a', but all sorts of other possibilies; t d epends on the Unix and in some cases even the specific version. - | |||||
| Cron At and Batch | 2000 01 | 2012/06/11 TonyLawrence | |||
| - Cron, Batch and At, including explanations of why it might not be working - | |||||
| Understanding Device files | 1998 | 2012/08/30 TonyLawrence | |||
| - Unix device files are not like ordinary files. Understanding their properties and use is very helpful. - | |||||
| What causes a Segmentation fault? | 2006 02 | 2010/11/01 lambros | |||
| - Short answer: it's most likely hardware unless you wrote the program or just now installed it on your machine. - | |||||
| difference between /dev/sr0 and /dev/scd0 | 1997-2004 | 2010/03/20 TonyLawrence | |||
| - why does the system call the same device by two different names: There isn't necessarily any difference at all. - | |||||
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| Invalidating the Linux buffer cache | 2006 12 | 2012/08/01 SimonL | |||
| - How to actually test the disk drive to know that data really has gotten to the disk drive. This could be because you want to test the performance of the drive, but could also be when you suspect a drive is malfunctioning: if you just write and read back, you'll be reading from cache, not from actual disk platters. - | |||||
| Linux|Unix ABI- Using other Unix binaries on Linux | 2001 11 | ||||
| - Linux ABI- pitfalls and considerations of running SCO apps on Linux - | |||||
| SPID, threads in ps | 2005 06 | ||||
| - The SPID column is the thread id. As far as I can tell, LWP and SPID are the same thing; I am not sure what the value of NLWP is; it appears to be just the count of threads. - | |||||
| Realtime-Preempt for the Linux kernel. | 2005 06 | ||||
| - The Linux kernel has always been somewhat preemptive, but with the 2.6 kernel there were big improvements aimed at making the kernel almost fully preemptive - | |||||
| Understanding IPTABLES | 2002 11 | 2012/11/29 BigDumbDinosaur | |||
| - Packet filtering is something I've always hard a hard time getting my head around. Not the basics; that's easy enough. It's just the incredible level of detail, the difficulty of keeping it all in your head at once. - | |||||
| Linux 2.6 | 2006 04 | ||||
| - This article highlights some of the performance and scalability improvements of the Linux 2.6 kernel. - | |||||
| Hobby Operating Systems | 2003 10 | 2010/12/03 anonymous | |||
| - With the possible exception of OpenBeOS and Syllable/Atheos, there's nothing there that is particularly different. Where are the real radical ideas, like a pure virtual memory OS that only uses disks as backing store or perhaps a network os where everything is packet based? Oh, well: maybe one of these will ring your chimes: - | |||||
| How much swap space do I need? | 1997-2003 | ||||
| - There are two factors to consider - how much you actually need for correct operation of your system, and how much you might need in case of a kernel panic. - | |||||
| Maximun number of socket connections | 2006 02 | ||||
| - 100 connections hangs server.. configuration? Possible tuning limits on SCO Unix that might cause this. - | |||||
| linux shmmax -->Re How to modify the value ofSHMMAX? | 1997-2004 | ||||
| - linux shmmax -->Re: How to modify the value ofSHMMAX? - | |||||
| Understanding Device Drivers | 1998 | ||||
| - Device Driver. Two words that strike fear in the hearts of programmers and users of Unix systems. - | |||||
| Where's the memory? | 2006 06 | ||||
| - Memory usage under Linux is full of surprises. Do not assume you know what's going on based upon your knowledge of other systems. - | |||||
| Essential Linux Device Drivers | 2008 05 | ||||
| - I admit that it's very hard to write a good book in this area. You simply have to make assumptions about the readers knowledge - if you don't, you'll be writing an encyclopedia or two. - | |||||
| What is a watchdog timer panic or error message? | 2009 09 | ||||
| - In general, a watchdog timer is a piece of code (or hardware) that attempts to keep another piece of code (or hardware) from getting stuck in an endless loop. - | |||||
| Process scheduling | 2004 08 | ||||
| - Process scheduling is obviously important on multi-user systems. It's also important on systems we use as individuals. For example, contrast the startup of my Mac OS X box and my wife's XP system. Both have certain programs set to start up at login, but they obviously handle the scheduling much differently. On the Mac, I can click into any process that has started and can use it while other programs are still starting. On XP, I can't: the other programs will command the CPU's attention until everything is running. - | |||||
| Panic- Trap 0x0000000E | 1999 07 | ||||
| - Technically, an E trap is a page fault that referenced an impossible page: the CPU tries to access an address that does not exist and can't be accessed. - | |||||
| Understanding the Unix Kernel | 2003 02 | ||||
| - I think that part of the problem is the deliberate "bottom-up" approach: this starts out in the first chapter dealing with memory addressing at the hardware level and goes on from there. - | |||||
| Booting SCO_OSR5- Kernel | 1999 09 | ||||
| - When you type the name of a kernel to get the kernel defined by defbootstr, /boot first checks to see that you haven't typed a built in command. - | |||||
| allocb failed NSTRPAGES exceeded streams memory netstat -m-->Re I can't find something! | 1997-2004 | ||||
| - You are running out of streams memory- run "netstat -m"- you'll likely see non-zero amounts in the Failures column. - | |||||
| Tape Autoloader on 2.4 Linux | 2003 01 | ||||
| - Rob Fantini explains how he got an autoloader tape unit working on RedHat Linux This info may not be clearly written, but shows what I did to get autoloaders working on 2.4 linux. - | |||||
| EAGAIN error -->Re Fork failing, but WHY?? | 1997-2004 | ||||
| - EAGAIN error -->Re: Fork failing, but WHY?? - | |||||
| IOMEGA REV Drive with Fedora Core 2 | 2004 09 | ||||
| - Unfortunately, that was a system I wanted to use the REV on. - | |||||
| Booting SCO_OSR5- Filesystems | 2000 01 | ||||
| - Just about anything you are going to do with a computer involves files. Unix in general treats just about everything as a file. - | |||||
| Badram, Badmem, and Memtest86.bin | 2005 02 | ||||
| - when you get almost-random stuff going wrong like that, and you know that your using what should be a fairly stable OS the likely culprit is going to be flaky hardware - | |||||
| TIME_WAIT network timeout tcp/ip /etc/default/inet -->ReFlushing kernel Routing Table | 1997-2004 | ||||
| - Changing tcp timeout settings on SCO unix 5.0.6. The value of tcp2mls which, as per RFC793, should be approx 4 minutes was set to 30 on SCO Unix! - | |||||
| Caches | 2003 09 | ||||
| - In the case of computer caches, we aren't trying to hide data, just make our access to it quicker or more convenient. - | |||||
| shmget ipcs shared memory -->Re Memory error relating toshmget | 1997-2004 | ||||
| - shmget ipcs shared memory -->Re: Memory error relating toshmget - | |||||
| GNU libc, glibc, Glib, glibc2, and libstdc++ | 1997-2004 | ||||
| - GNU libc is glibc. glibc2 is v2 of glibc. /lib/libc.so.6 is the library that implements glibc. You can check out which version, exactly, of glibc2 (aka glibc aka GNU libc) libc.so.6 implements by /running/ libc.so.6 - | |||||
| Booting SCO_OSR5 | 1999 12 | ||||
| - PC Bootstrap: I'm ignoring the POST (Power On Self Test) routines and anything else (security checks, etc) that might be built into your machine. Obviously all of that happens prior to boot, but isn't important for this article. - | |||||
| Understanding Device Drivers Part II | 1998 | ||||
| - When that interrupt comes that says the printer is ready, our driver program could be be filling the clist, or it could be sleeping because the clist is full. - | |||||
| Understanding Device Drivers Part III | 1998 | ||||
| - The first field after the name tells us the routines that are used in the driver. This driver has Open, Close, Read, Write, Ioctl and an Initialization routine. - | |||||
| slabtop, /proc/slabinfo | 2005 07 | ||||
| - If you ever noticed /proc/slabinfo, its contents surely mystified you. That documentation is as geeky as it gets. - | |||||
| Understanding Threads | 2003 10 | ||||
| - Threads are often described as lightweight processes, which is useful, but unless you understand ordinary Unix processes, that doesn't really tell you much. The traditional Unix model was fork and exec, which is "expensive" in terms of cpu time. However (and this is the part that often gets left out), that doesn't mean that fork and exec is "bad" and threads are "good": it depends upon what it is you need to accomplish. Even at that, there are other considerations, as we shall see. - | |||||
| TASK_KILLABLE | 2009 02 | ||||
| - Who hasn't been frustrated by some device stuck in a hardware read or write? Finally.. kill the unkillable. - | |||||
| Swap Prefetch Arguments | 2008 02 | ||||
| - Anticipation of swapping needs: The concept is simple enough: if stuff has been swapped because there wasn't room in RAM, but now there is because some program just exited, maybe the stuff that was swapped should be brought back now instead of waiting until it is actually needed. - | |||||
| Microsoft Windows Internals | 2008 01 | ||||
| - Windows internals book gives many insights: As most readers here know, I'm no fan of Microsoft. However, Microsoft operating systems are a big part of today's computer world. While I may hope for change (and I really believe there will be change over the next decade), I can't afford to ignore Microsoft entirely. Hence this book. If you have been a casual Microsoft programmer, hacker or support person, this will give you the tools and knowledge to step up. - | |||||
| SuperBox Mark I | 2008 01 | ||||
| - The mythical Superbox Mark I was not announced today: I had an exclusive opportunity to speak with Brian Casales, CEO of Gapple, Inc. about the heavily rumored upcoming "Superbox Mark I" that is supposed to shake our industry to its knees. - | |||||
| Solaris Performance Tools | 2006 07 | ||||
| - I'm not as fascinated by tuning as I used to be. Nevertheless, this was an interesting read. I did not know, Most of this book is about Dtrace (Sun's Dynamic Tracing Tool) and - | |||||
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| Solaris Internals | 2006 07 | ||||
| - Review of Solaris(TM) Internals : Solaris 10 and OpenSolaris Kernel Architecture (2nd Edition) - | |||||
| Protecting rm | 2006 06 | ||||
| - Should rm ask 'Are you sure?'. Should it ever question your authority or desires?1 - | |||||
| Free VMware server | 2006 02 | ||||
| - That's simply tremendous news, though I'm surprised by how many people I talk to who don't understand why this is so important. - | |||||
| How shells call other programs | 2006 02 | ||||
| - Kernel exec vs. shell interpretation: The implication is that the shell reads the command and decides what to do. It's actually the kernel that makes a lot of the decisions. - | |||||
| A ps problem with BBX | 2006 02 | ||||
| - The actual problem related to BBX. Apparently this gets run with very long command lines, which could not be seen in 'ps' - | |||||
| The Ancient Computer Time Machine | 2005 11 | ||||
| - The Ancient Computer Time Machine MITS ALtair, SPS, Ancient Unix R5 - | |||||
| The Linux Kernel Primer | 2005 10 | ||||
| - I've been less than happy with other kernel books I've read. Admittedly,it's a difficult subject: there's a lot to cover, and you really need quite a bit of programming and general Unix knowledge before you could even consider jumping into this area. But I have the background, have even written simple Unix drivers, and yet every other kernel programming book has disappointed me. - | |||||
| Jim Mohr's SCO Companion | 2005 07 | ||||
| - - | |||||
| Performance Tuning for Linux Servers | 2005 07 | ||||
| - I'm trying hard to like this more than I do. It's not that there isn't good stuff in here; there is. But I just can't get excited about it. - | |||||
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