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• Automatically kill processes that over time uses 95%+ of resources? Ubuntu

  - by data_jepp

  I don't know about you're computer but when mine is working properly no process is sucking 95%+ over time. I would like to have some failsafe that kills any processes behaving like that. This comes to mind because when I woke up this morning my laptop had been crunching all night long on a stray chromium child process. This can probably be done as a cron job, but before I make it a full time job creating something like this I'd thought I should check here. :) I hate reinventing the wheel.

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• C++ Simple thread with parameter (no .net)

  - by Marc Vollmer

  I've searched the internet for a while now and found different solutions but then all don't really work or are to complicated for my use. I used C++ until 2 years ago so it might be a bit rusty :D I'm currently writing a program that posts data to an URL. It only posts the data nothing else. For posting the data I use curl, but it blocks the main thread and while the first post is still running there will be a second post that should start. In the end there are about 5-6 post operations running at the same time. Now I want to push the posting with curl into another thread. One thread per post. The thread should get a string parameter with the content what to push. I'm currently stuck on this. Tried the WINAPI for windows but that crashes on reading the parameter. (the second thread is still running in my example while the main thread ended (waiting on system("pause")). It would be nice to have a multi plattform solution, because it will run under windows and linux! Heres my current code: #define CURL_STATICLIB #include <curl/curl.h> #include <curl/easy.h> #include <cstdlib> #include <iostream> #include <stdio.h> #include <stdlib.h> #include <string> #if defined(WIN32) #include <windows.h> #else //#include <pthread.h> #endif using namespace std; void post(string post) { // Function to post it to url CURL *curl; // curl object CURLcode res; // CURLcode object curl = curl_easy_init(); // init curl if(curl) { // is curl init curl_easy_setopt(curl, CURLOPT_URL, "http://10.8.27.101/api.aspx"); // set url string data = "api=" + post; // concat post data strings curl_easy_setopt(curl, CURLOPT_POSTFIELDS, data.c_str()); // post data res = curl_easy_perform(curl); // execute curl_easy_cleanup(curl); // cleanup } else { cerr << "Failed to create curl handle!\n"; } } #if defined(WIN32) DWORD WINAPI thread(LPVOID data) { // WINAPI Thread string pData = *((string*)data); // convert LPVOID to string [THIS FAILES] post(pData); // post it with curl } #else // Linux version #endif void startThread(string data) { // FUnction to start the thread string pData = data; // some Test #if defined(WIN32) CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)thread, &pData, 0, NULL); // Start a Windows thread with winapi #else // Linux version #endif } int main(int argc, char *argv[]) { // The post data to send string postData = "test1234567890"; startThread(postData); // Start the thread system("PAUSE"); // Dont close the console window return EXIT_SUCCESS; } Has anyone a suggestion? Thanks for the help!

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• How to force two process to run on the same CPU?

  - by kovan

  Context: I'm programming a software system that consists of multiple processes. It is programmed in C++ under Linux. and they communicate among them using Linux shared memory. Usually, in software development, is in the final stage when the performance optimization is made. Here I came to a big problem. The software has high performance requirements, but in machines with 4 or 8 CPU cores (usually with more than one CPU), it was only able to use 3 cores, thus wasting 25% of the CPU power in the first ones, and more than 60% in the second ones. After many research, and having discarded mutex and lock contention, I found out that the time was being wasted on shmdt/shmat calls (detach and attach to shared memory segments). After some more research, I found out that these CPUs, which usually are AMD Opteron and Intel Xeon, use a memory system called NUMA, which basically means that each processor has its fast, "local memory", and accessing memory from other CPUs is expensive. After doing some tests, the problem seems to be that the software is designed so that, basically, any process can pass shared memory segments to any other process, and to any thread in them. This seems to kill performance, as process are constantly accessing memory from other processes. Question: Now, the question is, is there any way to force pairs of processes to execute in the same CPU?. I don't mean to force them to execute always in the same processor, as I don't care in which one they are executed, altough that would do the job. Ideally, there would be a way to tell the kernel: If you schedule this process in one processor, you must also schedule this "brother" process (which is the process with which it communicates through shared memory) in that same processor, so that performance is not penalized.

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• POSIX AIO Library and Callback Handlers

  - by Charles Salvia

  According to the documentation on aio_read/write, there are basically 2 ways that the AIO library can inform your application that an async file I/O operation has completed. Either 1) you can use a signal, 2) you can use a callback function I think that callback functions are vastly preferable to signals, and would probably be much easier to integrate into higher-level multi-threaded libraries. Unfortunately, the documentation for this functionality is a mess to say the least. Some sources, such as the man page for the sigevent struct, indicate that you need to set the sigev_notify data member in the sigevent struct to SIGEV_CALLBACK and then provide a function handler. Presumably, the handler is invoked in the same thread. Other documentation indicates you need to set sigev_notify to SIGEV_THREAD, which will invoke the callback handler in a newly created thread. In any case, on my Linux system (Ubuntu with a 2.6.28 kernel) SIGEV_CALLBACK doesn't seem to be defined anywhere, but SIGEV_THREAD works as advertised. Unfortunately, creating a new thread to invoke the callback handler seems really inefficient, especially if you need to invoke many handlers. It would be better to use an existing pool of threads, similar to the way most network I/O event demultiplexers work. Some versions of UNIX, such as QNX, include a SIGEV_SIGNAL_THREAD flag, which allows you to invoke handlers using a specified existing thread, but this doesn't seem to be available on Linux, nor does it seem to even be a part of the POSIX standard. So, is it possible to use the POSIX AIO library in a way that invokes user handlers in a pre-allocated background thread/threadpool, rather than creating/destroying a new thread everytime a handler is invoked?

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• Creating customized .dmg files upon download

  - by Marten

  I want to distribute a cross-platform application for which the executable file is slightly different, depending on the user who downloaded it. This is done by having a placeholder string somewhere in the executable that is replaced with something user-specific upon download. The webserver that has to do these string replacements is a Linux machine. For Windows, the executable is not compressed in the installer .exe, so the string replacement is easy. For uncompressed Mac OS X .dmg files, this is also easy. However, .dmg files that are compressed with either gzip or bzip2 are not so easy. For example, in the latter case, the compressed .dmg is not one big bzip2-compressed disk image, but instead consists of a few different bzip2-compressed parts (with different block sizes) and a plist suffix. Also, decompressing and recompressing the different parts with bzip2 does not result in the original data, so I'm guessing Apple uses some different parameters to bzip2 than the command-line tool. Is there a way to generate a compressed .dmg from an uncompressed one on Linux (which does not have hdiutil)? Or maybe another suggestion for creating customized applications without pregenerating them? It should work without any input by the user.

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• Including variables inside curly braces in a Zend config ini file on Linux

  - by Dave Morris

  I am trying to include a variable in a .ini file setting by surrounding it with curly braces, and Zend is complaining that it cannot parse it properly on Linux. It works properly on Windows, though: welcome_message = Welcome, {0}. This is the error that is being thrown on Linux: : Uncaught exception 'Zend_Config_Exception' with message 'Error parsing /var/www/html/portal/application/configs/language/messages.ini on line 10 ' in /usr/local/zend/share/ZendFramework/library/Zend/Config/Ini.php:181 Stack trace: 0 /usr/local/zend/share/ZendFramework/library/Zend/Config/Ini.php(201): Zend_Config_Ini-&gt;_parseIniFile('/var/www/html/p...') 1 /usr/local/zend/share/ZendFramework/library/Zend/Config/Ini.php(125): Zend_Config_Ini-&gt;_loadIniFile('/var/www/html/p...') 2 /var/www/html/portal/library/Ingrain/Language/Base.php(49): Zend_Config_Ini-&gt;__construct('/var/www/html/p...', NULL) 3 /var/www/html/portal/library/Ingrain/Language/Base.php(23): Ingrain_Language_Base-&gt;setConfig('messages.ini', NULL, NULL) 4 /var/www/html/portal/library/Ingrain/Language/Messages.php(7): Ingrain_Language_Base-&gt;__construct('messages.ini', NULL, NULL, NULL) 5 /var/www/html/portal/library/Ingrain/Helper/Language.php(38): Ingrain_Language_Messages-&gt;__construct() 6 /usr/local/zend/share/ZendFramework/library/Zend/Contr in We are able to get the error to go away on Linux if we surround the braces with quotes, but that seems like a strange solution: welcome_message = Welcome, "{"0"}". Is there a better way to solve this issue for all platforms? Thanks for your help, Dave

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• Finding missing symbols in libstd++ on Debian/squeeze

  - by Florian Le Goff

  I'm trying to use a pre-compiled library provided as a .so file. This file is dynamically linked against a few librairies : $ ldd /usr/local/test/lib/libtest.so linux-gate.so.1 = (0xb770d000) libstdc++-libc6.1-1.so.2 = not found libm.so.6 = /lib/i686/cmov/libm.so.6 (0xb75e1000) libc.so.6 = /lib/i686/cmov/libc.so.6 (0xb7499000) /lib/ld-linux.so.2 (0xb770e000) libgcc_s.so.1 = /lib/libgcc_s.so.1 (0xb747c000) Unfortunately, in Debian/squeeze, there is no libstdc++-libc6.1-1.so.* file. Only a libstdc++.so.* file provided by the libstdc++6 package. I tried to link (using ln -s) libstdc++-libc6.1-1.so.2 to the libstdc++.so.6 file. It does not work, a batch of symbols seems to be lacking when I'm trying to ld my .o files with this lib. /usr/local/test/lib/libtest.so: undefined reference to `__builtin_vec_delete' /usr/local/test/lib/libtest.so: undefined reference to `istrstream::istrstream(int, char const *, int)' /usr/local/test/lib/libtest.so: undefined reference to `__rtti_user' /usr/local/test/lib/libtest.so: undefined reference to `__builtin_new' /usr/local/test/lib/libtest.so: undefined reference to `istream::ignore(int, int)' What would you do ? How may I find in which lib those symbols are exported ?

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• Convert MFC Doc/View to?

  - by Harvey

  My question will be hard to form, but to start: I have an MFC SDI app that I have worked on for an embarrassingly long time, that never seemed to fit the Doc/View architecture. I.e. there isn't anything useful in the Doc. It is multi-threaded and I need to do more with threading, etc. I dream about also porting it to Linux X Windows, but I know nothing about that programming environment as yet. Maybe Mac also. My question is where to go from here? I think I would like to convert from MFC Doc/View to straight Win API stuff with message loops and window procedures, etc. But the task seems to be huge. Does the Linux X Windows environment use a similar kind of message loop, window procedure architecture? Can I go part way? Like convert a little at a time without rendering my program unusable for long periods of work? What is the best book to read to help me to move in that direction.

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• is it possible to turn off vdso on glibc side?

  - by heroxbd

  I am aware that passing vdso=0 to kernel can turn this feature off, and that the dynamic linker in glibc can automatic detect and use vdso feature from kernel. Here I met with this problem. There is a RHEL 5.6 box (kernel 2.6.18-238.el5) in my institution where I only have a normal user access, probably suffering from RHEL bug 673616. As I compile a toolchain of linux-headers-3.9/gcc-4.7.2/glibc-2.17/binutils-2.23 on top of it, gcc bootstrap fails in cc1 in stage2 cannnot be run Program received signal SIGSEGV, Segmentation fault. 0x00002aaaaaaca6eb in ?? () (gdb) info sharedlibrary From To Syms Read Shared Object Library 0x00002aaaaaaabba0 0x00002aaaaaac3249 Yes (*) /home/benda/gnto/lib64/ld-linux-x86-64.so.2 0x00002aaaaacd29b0 0x00002aaaaace2480 Yes (*) /home/benda/gnto/usr/lib/libmpc.so.3 0x00002aaaaaef2cd0 0x00002aaaaaf36c08 Yes (*) /home/benda/gnto/usr/lib/libmpfr.so.4 0x00002aaaab14f280 0x00002aaaab19b658 Yes (*) /home/benda/gnto/usr/lib/libgmp.so.10 0x00002aaaab3b3060 0x00002aaaab3b3b50 Yes (*) /home/benda/gnto/lib/libdl.so.2 0x00002aaaab5b87b0 0x00002aaaab5c4bb0 Yes (*) /home/benda/gnto/usr/lib/libz.so.1 0x00002aaaab7d0e70 0x00002aaaab80f62c Yes (*) /home/benda/gnto/lib/libm.so.6 0x00002aaaaba70d40 0x00002aaaabb81aec Yes (*) /home/benda/gnto/lib/libc.so.6 (*): Shared library is missing debugging information. and a simple program #include <sys/time.h> #include <stdio.h> int main () { struct timeval tim; gettimeofday(&tim, NULL); return 0; } get segment fault in the same way if compiled against glibc-2.17 and xgcc from stage1. Both cc1 and the test program can be run on another running RHEL 5.5 (kernel 2.6.18-194.26.1.el5) with gcc-4.7.2/glibc-2.17/binutils-2.23 as normal user. I cannot simply upgrade the box to a newer RHEL version, nor could I turn VDSO off via sysctl or proc. The question is, is there a way to compile glibc so that it turns off VDSO unconditionally?

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• Why does gcc generate verbose assembly code?

  - by Jared Nash

  I have a question about assembly code generated by GCC (-S option). Since, I am new to assembly language and know very little about it, the question will be very primitive. Still, I hope somebody will answer: Suppose, I have this C code: main(){ int x = 15; int y = 6; int z = x - y; return 0; } If we look at the assembly code (especially the part corresponding to int z = x - y ), we see: main: ... subl $16, %esp movl $15, -4(%ebp) movl $6, -8(%ebp) movl -8(%ebp), %eax movl -4(%ebp), %edx movl %edx, %ecx subl %eax, %ecx movl %ecx, %eax movl %eax, -12(%ebp) ... Why doesn't GCC generate something like this, which is less copying things around. main: ... movl $15, -4(%ebp) movl $6, -8(%ebp) movl -8(%ebp), %edx movl -4(%ebp), %eax subl %edx, %eax movl %eax, -12(%ebp) ... P.S. Linux zion-5 2.6.32-21-generic #32-Ubuntu SMP Fri Apr 16 08:10:02 UTC 2010 i686 GNU/Linux gcc version 4.4.3 (Ubuntu 4.4.3-4ubuntu5)

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• Cutting Ubuntu to the bone for Virtualbox VM

  - by Monty

  I've been looking around for a Linux variant which will install only the software I need rather than everything Ubuntu (for example) puts in by default. This is to create a virtual machine in Virtualbox which has bash, apache, python, perl, SQLite, openssh and a few other programs but nothing else. I'd prefer to go with Ubuntu if possible but another modern distro would do as well (I like using apt-get and yum rather than downloading/compiling etc). So far, I've tried: SuseStudio.com, which is probably the best so far. Pressing F4 to get the boot options on Ubuntu 9.10, but there is no minimal installation (I think there was once). Arch Linux, slightly confusing install procedure but I might go back and try again. Gentoo, started well but fairly soon the HD on the virtual machine went to 2Gb, even before the installation had started in earnest (I'd partitioned the disks is all). I realise there are various "small" Linuxes around like Puppy, Feather, DSL, etc, but they seem to be aimed at desktop users or as a techie's toolkit, and I want a small-as-possible server distro which can be managed with tools like apt or yum or similar. TIA for any advice you can offer! -- Monty

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• Problem in accessing Windows shared folder on Ubuntu using terminal

  - by vikramtheone

  Hi Guys, Description I have 2 systems with me, one running on Windows(Host) and one on Ubuntu, both on a LAN. On the Windows(Host) I develop software intended for the Linux system and because the Linux system has little external memory, my idea to overcome this is by making the project folder on the Host side a Shared Folder with full access and access it on Ubuntu over the network. To achieve this, I have installed Samba on Ubuntu, when I go to Places -> Network I can see the shared project folder and I simply mount it. A link appears on the desktop. Next, using Nautilus I open the link and I can access the contents of the shared folder. Problem Even though I mount the shared project folder, I don't see it appearing in the /media or the /mnt folder, as a result of this I don't know what path to use to access this folder, from the terminal. For example: When, I mounted my USB stick, as expected, a link for the device appears on the Desktop and I also see a folder in the media folder. So, similarly, a mounted shared folder should have appeared on the /mnt folder, too. Can anyone suggest what I should do now? There are many posts around, but no solid solution for this problem. Help!!! :) Vikram

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• why it is not possible to modify file in a directory, where i have read/write group rights

  - by sighter

  I am currently messing around on my linux system and now i have the following situation. The directory /srv/http has the following permissions set: drwxrwxr-x 2 root httpdev 80 Jun 13 11:48 ./ drwxr-xr-x 6 root root 152 Mar 26 13:56 ../ -rwxrwxr-x 1 root httpdev 8 Jun 13 11:48 index.html* I have created the group httpdev before with the command: groupadd httpdev and added my user sighter with: gpasswd -a sighter httpdev Then i have set the permissions as above using the chown and chmod commands. But now i am not allowed to modify the index.html file or create a new file, as user sighter ,with touch like that: <sighter [bassment] ~http> touch hallo.php touch: cannot touch `hallo.php': Permission denied What do I understand wrong. I was expecting that i can do what i want there then the group has all the rights. The following Output is for your in formation. <sighter [bassment] ~http> cat /etc/group | grep sighter ... httpdev:x:1000:sighter ... The used linux-distro is archlinux. Thanks for all answers :) greetz Sascha

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• Python virtualenv questions

  - by orokusaki

  I'm using VirtualEnv on Windows XP. I'm wondering if I have my brain wrapped around it correctly. I ran virtualenv ENV and it created C:\WINDOWS\system32\ENV. I then changed my PATH variable to include C:\WINDOWS\system32\ENV\Scripts instead of C:\Python27\Scripts. Then, I checked out Django into C:\WINDOWS\system32\ENV\Lib\site-packages\django-trunk, updated my PYTHON_PATH variable to point the new Django directory, and continued to easy_install other things (which of course go into my new C:\WINDOWS\system32\ENV\Lib\site-packages directory). I understand why I should use VirtualEnv so I can run multiple versions of Django, and other libraries on the same machine, but does this mean that to switch between environments I have to basically change my PATH and PYTHON_PATH variable? So, I go from developing one Django project which uses Django 1.2 in an environment called ENV and then change my PATH and such so that I can use an environment called ENV2 which has the dev version of Django? Is that basically it, or is there some better way to automatically do all this (I could update my path in Python code, but that would require me to write machine-specific code in my application)? Also, how does this process compare to using VirtualEnv on Linux (I'm quite the beginner at Linux).

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• Shared Memory and Process Sempahores (IPC)

  - by fsdfa

  This is an extract from Advanced Liniux Programming: Semaphores continue to exist even after all processes using them have terminated. The last process to use a semaphore set must explicitly remove it to ensure that the operating system does not run out of semaphores.To do so, invoke semctl with the semaphore identifier, the number of semaphores in the set, IPC_RMID as the third argument, and any union semun value as the fourth argument (which is ignored).The effective user ID of the calling process must match that of the semaphore’s allocator (or the caller must be root). Unlike shared memory segments, removing a semaphore set causes Linux to deallocate immediately. If a process allocate a shared memory, and many process use it and never set to delete it (with shmctl), if all them terminate, then the shared page continues being available. (We can see this with ipcs). If some process did the shmctl, then when the last process deattached, then the system will deallocate the shared memory. So far so good (I guess, if not, correct me). What I dont understand from that quote I did, is that first it say: "Semaphores continue to exist even after all processes using them have terminated." and then: "Unlike shared memory segments, removing a semaphore set causes Linux to deallocate immediately."

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• Setting the default stack size on Linux globally for the program

  - by wowus

  So I've noticed that the default stack size for threads on linux is 8MB (if I'm wrong, PLEASE correct me), and, incidentally, 1MB on Windows. This is quite bad for my application, as on a 4-core processor that means 64 MB is space is used JUST for threads! The worst part is, I'm never using more than 100kb of stack per thread (I abuse the heap a LOT ;)). My solution right now is to limit the stack size of threads. However, I have no idea how to do this portably. Just for context, I'm using Boost.Thread for my threading needs. I'm okay with a little bit of #ifdef hell, but I'd like to know how to do it easily first. Basically, I want something like this (where windows_* is linked on windows builds, and posix_* is linked under linux builds) // windows_stack_limiter.c int limit_stack_size() { // Windows impl. return 0; } // posix_stack_limiter.c int limit_stack_size() { // Linux impl. return 0; } // stack_limiter.cpp int limit_stack_size(); static volatile int placeholder = limit_stack_size(); How do I flesh out those functions? Or, alternatively, am I just doing this entirely wrong? Remember I have no control over the actual thread creation (no new params to CreateThread on Windows), as I'm using Boost.Thread.

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• How frequently IP packets are fragmented at the source host?

  - by Methos

  I know that if IP payload MTU then routers usually fragment the IP packet. Finally all the fragmented packets are assembled at the destination using the fields IP-ID, IP fragment offsets and fragmentation flags. Max length of IP payload is 64K. Thus its very plausible for L4 to hand over payload which is 64K. If the L2 protocol is Ethernet, which often is the case, then the MTU will be about 1600 bytes. Hence IP packet will be fragmented at the source host itself. However, a quick search about IP implementation in Linux tells me that in recent kernels, L4 protocols are fragment friendly i.e. they try to save the fragmentation work for IP by handing over buffers of size which is close to MTU. Considering these two facts, I am wondering about how frequently does the IP packet gets fragmented at the source host itself. Does it occur sometimes/rarely/never? Does anyone know if there are exceptions to the rule of fragmentation in linux kernel (i.e. are there situations where L4 protocols are not fragment friendly)? How is this handled in other common OSes like windows? In general how frequently IP packets are fragmented?

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• Finding missing files by checksum

  - by grw

  Hi there, I'm doing a large data migration between two file systems (let's call them F1 and F2) on a Linux system which will necessarily involve copying the data verbatim into a differently-structured hierarchy on F2 and changing the file names. I'd like to write a script to generate a list of files which are in F1 but not in F2, i.e. the ones which weren't copied by the migration script into the new hierarchy, so that I can go back and migrate them manually. Unfortunately for reasons not worth going into, the migration script can't be modified to list files that it doesn't migrate. My question differs from this previously answered one because of the fact that I cannot rely on filenames as a comparison. I know the basic outline of the process would be: Generate a list of checksums for all files, recursing through F1 Do the same for F2 Compare the lists and generate a negative intersection of the checksums, ignoring the file names, to find files which are in F1 but not in F2. I'm kind of stuck getting past that stage, so I'd appreciate any pointers on which tools to use. I think I need to use the 'comm' command to compare the list of file checksums, but since md5sum, sha512sum and the like put the file name next to the checksum, I can't see a way to get it to bring me a useful comparison. Maybe awk is the way to go? I'm using Red Hat Enterprise Linux 5.x. Thanks.

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• Freeing of allocated memory in Solaris/Linux

  - by user355159

  Hi, I have written a small program and compiled it under Solaris/Linux platform to measure the performance of applying this code to my application. The program is written in such a way, initially using sbrk(0) system call, i have taken base address of the heap region. After that i have allocated an 1.5GB of memory using malloc system call, Then i used memcpy system call to copy 1.5GB of content to the allocated memory area. Then, I freed the allocated memory. After freeing, i used again sbrk(0) system call to view the heap size. This is where i little confused. In solaris, eventhough, i freed the memory allocated (of nearly 1.5GB) the heap size of the process is huge. But i run the same application in linux, after freeing, i found that the heap size of the process is equal to the size of the heap memory before allocation of 1.5GB. I know Solaris does not frees memory immediately, but i don't know how to tune the solaris kernel to immediately free the memory after free() system call. Also, please explain why the same problem does not comes under Linux? Can anyone help me out of this? Thanks, Santhosh.

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• Portable way of counting milliseconds in C++ ?

  - by ereOn

  Hi, Is there any portable (Windows & Linux) way of counting how many milliseconds elapsed between two calls ? Basically, I want to achieve the same functionnality than the StopWatch class of .NET. (for those who already used it) In a perfect world, I would have used boost::date_time but that's not an option here due to some silly rules I'm enforced to respect. For those who better read code, this is what I'd like to achieve. Timer timer; timer.start(); // Some instructions here timer.stop(); // Print out the elapsed time std::cout << "Elapsed time: " << timer.milliseconds() << "ms" << std::endl; So, if there is a portable (set of) function(s) that can help me implement the Timer class, what is it ? If there is no such function, what Windows & Linux API should I use to achieve this functionnality ? (using #ifdef WINDOWS-like macros) Thanks !

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• PHP shell_exec() - Run directly, or perform a cron (bash/php) and include MySQL layer?

  - by Jimbo

  Sorry if the title is vague - I wasn't quite sure how to word it! What I'm Doing I'm running a Linux command to output data into a variable, parse the data, and output it as an array. Array values will be displayed on a page using PHP, and this PHP page output is requested via AJAX every 10 seconds so, in effect, the data will be retrieved and displayed/updated every 10 seconds. There could be as many as 10,000 characters being parsed on every request, although this is usually much lower. Alternative Idea I want to know if there is a better* alternative method of retrieving this data every 10 seconds, as multiple users (<10) will be having this command executed automatically for them. A cronjob running on the server could execute either bash or php (which is faster?) to grab the data and store it in a MySQL database. Then, any AJAX calls to the PHP output would return values in the MySQL database rather than making a direct call to execute server code every 10 seconds. Why? I know there are security concerns with running execs directly from PHP, and (I hope this isn't micro-optimisation) I'm worried about CPU usage on the server. The server is running a sempron processor. Yes, they do still exist. Having this only execute when the user is on the page (idea #1) means that the server isn't running code that doesn't need to be run. However, is this slow and insecure? Just in case the type of linux command may be of assistance in determining it's efficiency: shell_exec("transmission-remote $host:$port --auth $username:$password -l"); I'm hoping that there are differences in efficiency and level of security with the two methods I have outlined above, and that this isn't just micro-micro-optimisation. If there are alternative methods that are better*, I'd love to learn about these! :)

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• Perl Linux::Inotify2 - can't respond to events anymore

  - by alcy

  I am getting some really weird behavior when using Linux::Inotify2 module for watching a directory for any newly created files. I had made a test script to see how it worked, and once that was done, I went on to incorporating its usage in the other scripts, in which it didn't work. Then, when I tried my earlier test script again to find some information, strangely that stopped working as well. It hasn't worked since then. There were no package/distro upgrades during that time. The problem is that it has stopped responding to events. Here's the test script: #!/usr/bin/perl use strict; use warnings; use Linux::Inotify2; my $inotify = new Linux::Inotify2 or die "unable to create new inotify object: $!"; my $dir = "/my/dir"; $inotify->watch($dir, IN_CREATE, sub { my $e = shift; print $e->fullname; }) or die " Can't watch $!"; 1 while $inotify->poll; A strace on the running script kills the script. Otherwise when strace is used when starting the script, then it does seem to read the new events, but there's no response to those events. Any suggestions for debugging this further ?

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• OpenGL (glx) not working with ubuntu 12.10

  - by user26766

  It all started when I installed nvidia's own (download from website) driver. Uninstalling it and reverting back to nvidia-current didn't solve the problem, so I have been playing with this for a while. It seems glx support is missing, and my intel graphics is not responding. gnome loads only in fallback mode. Here are some outputs: glxinfo name of display: :0.0 Error: couldn't find RGB GLX visual or fbconfig glxgears Error: couldn't get an RGB, Double-buffered visual optirun glxgears works fine lspci | grep VGA 00:02.0 VGA compatible controller: Intel Corporation 2nd Generation Core Processor Family Integrated Graphics Controller (rev 09) 01:00.0 VGA compatible controller: NVIDIA Corporation GF108 [GeForce GT 540M] (rev ff) Here's the content of log file when just after running glxinfo: less /var/log/Xorg.0.log | grep gl [ 112.156] (II) LoadModule: "glx" [ 112.157] (II) Loading /usr/lib/xorg/modules/extensions/libglx.so [ 112.157] (II) Module glx: vendor="X.Org Foundation" [ 112.157] (II) UnloadModule: "glx" [ 112.157] (II) Unloading glx [ 112.157] (EE) Failed to load module "glx" (module requirement mismatch, 0) Some more info... lsmod Module Size Used by bbswitch 13612 0 pci_stub 12623 1 vboxpci 23195 0 vboxnetadp 25671 0 vboxnetflt 23480 0 vboxdrv 320372 3 vboxpci,vboxnetadp,vboxnetflt parport_pc 32689 0 ppdev 17074 0 bnep 18141 2 rfcomm 46620 12 binfmt_misc 17501 1 snd_hda_codec_hdmi 32049 1 snd_hda_codec_realtek 78147 1 joydev 17458 0 uvcvideo 76750 0 videobuf2_core 32852 1 uvcvideo videodev 120310 2 uvcvideo,videobuf2_core videobuf2_vmalloc 12861 1 uvcvideo videobuf2_memops 13405 1 videobuf2_vmalloc snd_hda_intel 33492 3 coretemp 13401 0 kvm_intel 132760 0 arc4 12530 2 snd_hda_codec 134213 3 snd_hda_codec_hdmi,snd_hda_codec_realtek,snd_hda_intel kvm 414111 1 kvm_intel iwlwifi 386837 0 i915 520799 2 snd_hwdep 17699 1 snd_hda_codec snd_pcm 96668 3 snd_hda_codec_hdmi,snd_hda_intel,snd_hda_codec psmouse 100389 0 drm_kms_helper 49113 1 i915 ghash_clmulni_intel 13221 0 snd_seq_midi 13325 0 snd_rawmidi 30513 1 snd_seq_midi btusb 22475 0 drm 288436 3 i915,drm_kms_helper serio_raw 13216 0 snd_seq_midi_event 14900 1 snd_seq_midi snd_seq 61555 2 snd_seq_midi,snd_seq_midi_event mac80211 535936 1 iwlwifi bluetooth 209249 22 bnep,rfcomm,btusb snd_timer 29426 2 snd_pcm,snd_seq snd_seq_device 14498 3 snd_seq_midi,snd_rawmidi,snd_seq snd 78921 16 snd_hda_codec_hdmi,snd_hda_codec_realtek,snd_hda_intel,snd_hda_codec,snd_hwdep,snd_pcm,snd_rawmidi,snd_seq,snd_timer,snd_seq_device cfg80211 206797 2 iwlwifi,mac80211 aesni_intel 51038 1 cryptd 20404 2 ghash_clmulni_intel,aesni_intel aes_x86_64 17256 1 aesni_intel dell_wmi 12682 0 sparse_keymap 13891 1 dell_wmi dcdbas 14439 0 i2c_algo_bit 13414 1 i915 microcode 22804 0 lpc_ich 17062 0 soundcore 15048 1 snd snd_page_alloc 18485 2 snd_hda_intel,snd_pcm video 19391 1 i915 mac_hid 13206 0 wmi 19071 1 dell_wmi mei 40691 0 lp 17760 0 parport 46346 3 parport_pc,ppdev,lp ahci 25721 3 libahci 31192 1 ahci atl1c 41102 0 how can I fix this? any ideas? Here is another thing I've tried: sudo apt-get purge nvidia* sudo reboot sudo apt-get install bumblebee bumblebee-nvidia didn't make any difference. The most relevant post I found on the web was this: http://ubuntuforums.org/archive/index.php/t-1722306.html Here it's explained that the problem is with the priority of shared libraries that are loaded for glxinfo. Here's what I get when I look up the libraries: linux-vdso.so.1 => (0x00007fff6bf8b000) libGL.so.1 => /usr/lib/x86_64-linux-gnu/mesa/libGL.so.1 (0x00007f22d6ccd000) libX11.so.6 => /usr/lib/x86_64-linux-gnu/libX11.so.6 (0x00007f22d6993000) libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f22d65d3000) libglapi.so.0 => /usr/lib/x86_64-linux-gnu/libglapi.so.0 (0x00007f22d63ad000) libXext.so.6 => /usr/lib/x86_64-linux-gnu/libXext.so.6 (0x00007f22d619b000) libXdamage.so.1 => /usr/lib/x86_64-linux-gnu/libXdamage.so.1 (0x00007f22d5f97000) libXfixes.so.3 => /usr/lib/x86_64-linux-gnu/libXfixes.so.3 (0x00007f22d5d91000) libX11-xcb.so.1 => /usr/lib/x86_64-linux-gnu/libX11-xcb.so.1 (0x00007f22d5b8f000) libxcb-glx.so.0 => /usr/lib/x86_64-linux-gnu/libxcb-glx.so.0 (0x00007f22d5977000) libxcb.so.1 => /usr/lib/x86_64-linux-gnu/libxcb.so.1 (0x00007f22d5759000) libXxf86vm.so.1 => /usr/lib/x86_64-linux-gnu/libXxf86vm.so.1 (0x00007f22d5553000) libdrm.so.2 => /usr/lib/x86_64-linux-gnu/libdrm.so.2 (0x00007f22d5346000) libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007f22d5129000) libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007f22d4f25000) /lib64/ld-linux-x86-64.so.2 (0x00007f22d6f54000) libXau.so.6 => /usr/lib/x86_64-linux-gnu/libXau.so.6 (0x00007f22d4d20000) libXdmcp.so.6 => /usr/lib/x86_64-linux-gnu/libXdmcp.so.6 (0x00007f22d4b1a000) librt.so.1 => /lib/x86_64-linux-gnu/librt.so.1 (0x00007f22d4911000) It seems "mesa" instead of nvidia-current is being used. However I didn't find any obvious link to /lib/nvidia-current in /etc/ld.so.conf (where the directories containing the shared libraries are listed). I don't know if there's anything missing or if this is normal. thanks, UPDATE: The problem was solved by updating to Ubuntu 13.04. It seems bumblebee was to blame, but I'm not sure what was going wrong...

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• Networking issues with Linux server (CentOS 5.3)

  - by sxanness

  I have a Linux server hosting our bug tracking software (CentOS 5.2 Kernel 2.6.18-128.4.1.el5) that I have having some strange network problems with. The machine is configured with two NICS, one for the public interface and the other for our server back end network. The problem is that after doing a service network restart I can ping the public interface and it sends anywhere from 200-500 ICMP packets and then all of a sudden I start getting a request timed out error. Strange but as soon as I connect to the private interface the ping starts working again to the public interface. I clearly have a routing issue somewhere. I have a Juniper Router with the following configuration. Interface 0/0 -- Connect subnet to the ISP at our co-location Interface 0/2 -- For our DRAC network Interface 0/3 -- The Server-backend network (plugs directly into a switch that feeds to all the NICs that are on the 10.3.20.x network. Interface 0/4 -- Plugs directly into another switch that feeds our public interfaces, that interface as all the gateways from our public ip rangs as secondary IP addresses. I hope that someone can ask the right questions that can lead me to check things and figure out what is going on. Has anyone had similar problems and what kind of things should I be checking? Routing issue or something even more complicated? [root@fogbugz ~]# cat /etc/sysconfig/network-scripts/ifcfg-eth0 # Realtek Semiconductor Co., Ltd. RTL-8139/8139C/8139C+ DEVICE=eth0 BOOTPROTO=static IPADDR=72.249.134.98 NETMASK=255.255.255.248 BROADCAST=72.249.134.103 HWADDR=00:16:3E:AA:BB:EE ONBOOT=yes [root@fogbugz ~]# cat /etc/sysconfig/network-scripts/ifcfg-eth1 # Realtek Semiconductor Co., Ltd. RTL-8139/8139C/8139C+ DEVICE=eth1 BOOTPROTO=static BROADCAST=10.3.20.255 HWADDR=00:17:3E:AA:BB:EE IPADDR=10.3.20.25 NETMASK=255.255.255.0 NETWORK=10.3.20.0 ONBOOT=yes [root@fogbugz ~]# cat /etc/sysconfig/network NETWORKING=yes NETWORKING_IPV6=no HOSTNAME=fogbugz.dfw.hisg-it.net GATEWAY=72.249.134.97 [root@fogbugz ~]# route -n Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 72.249.134.96 0.0.0.0 255.255.255.248 U 0 0 0 eth0 10.3.20.0 0.0.0.0 255.255.255.0 U 0 0 0 eth1 169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0 eth1 10.0.0.0 10.3.20.1 255.0.0.0 UG 0 0 0 eth1 0.0.0.0 72.249.134.97 0.0.0.0 UG 0 0 0 eth0

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• Networking issues with Linux server (CentOS 5.3)

  - by sxanness

  I have a Linux server hosting our bug tracking software (CentOS 5.2 Kernel 2.6.18-128.4.1.el5) that I have having some strange network problems with. The machine is configured with two NICS, one for the public interface and the other for our server back end network. The problem is that after doing a service network restart I can ping the public interface and it sends anywhere from 200-500 ICMP packets and then all of a sudden I start getting a request timed out error. Strange but as soon as I connect to the private interface the ping starts working again to the public interface. I clearly have a routing issue somewhere. I have a Juniper Router with the following configuration. Interface 0/0 -- Connect subnet to the ISP at our co-location Interface 0/2 -- For our DRAC network Interface 0/3 -- The Server-backend network (plugs directly into a switch that feeds to all the NICs that are on the 10.3.20.x network. Interface 0/4 -- Plugs directly into another switch that feeds our public interfaces, that interface as all the gateways from our public ip rangs as secondary IP addresses. I hope that someone can ask the right questions that can lead me to check things and figure out what is going on. Has anyone had similar problems and what kind of things should I be checking? Routing issue or something even more complicated? [root@fogbugz ~]# cat /etc/sysconfig/network-scripts/ifcfg-eth0 # Realtek Semiconductor Co., Ltd. RTL-8139/8139C/8139C+ DEVICE=eth0 BOOTPROTO=static IPADDR=72.249.134.98 NETMASK=255.255.255.248 BROADCAST=72.249.134.103 HWADDR=00:16:3E:AA:BB:EE ONBOOT=yes [root@fogbugz ~]# cat /etc/sysconfig/network-scripts/ifcfg-eth1 # Realtek Semiconductor Co., Ltd. RTL-8139/8139C/8139C+ DEVICE=eth1 BOOTPROTO=static BROADCAST=10.3.20.255 HWADDR=00:17:3E:AA:BB:EE IPADDR=10.3.20.25 NETMASK=255.255.255.0 NETWORK=10.3.20.0 ONBOOT=yes [root@fogbugz ~]# cat /etc/sysconfig/network NETWORKING=yes NETWORKING_IPV6=no HOSTNAME=fogbugz.dfw.hisg-it.net GATEWAY=72.249.134.97 [root@fogbugz ~]# route -n Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 72.249.134.96 0.0.0.0 255.255.255.248 U 0 0 0 eth0 10.3.20.0 0.0.0.0 255.255.255.0 U 0 0 0 eth1 169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0 eth1 10.0.0.0 10.3.20.1 255.0.0.0 UG 0 0 0 eth1 0.0.0.0 72.249.134.97 0.0.0.0 UG 0 0 0 eth0

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