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  • Doubts in System call mechanism in linux

    - by bala1486
    We transit from ring3 to ring0 using 'int' or the new 'syscall/sysenter' instruction. Does that mean that the page tables and other stuffs that needs to be modified for the kernel is automatically done by the 'int' instruction or the interrupt handler for the 'int 0x80' will do the required stuff and jump to the respective system call. Also when returning from a system call, we again need to go to user space. For this we need to know the instruction address in the user space to continue the user application. Where is that address stored. Does the 'ret' instruction automatically changes the ring from ring3 to ring0 or where/how this ring changing mechanism takes place? Then, i read that changing from ring3 to ring0 is not as costly as changing from ring0 to ring3. Why is this so?? Thanks, Bala

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  • Measuring execution time of a system call in C++

    - by jm1234567890
    I have found some code on measuring execution time here http://www.dreamincode.net/forums/index.php?showtopic=24685 However, it does not seem to work for system calls. I imagine this is because the execution jumps out of the current process. clock_t begin=clock(); system(something); clock_t end=clock(); cout<<"Execution time: "<<diffclock(end,begin)<<" s."<<endl; Then double diffclock(clock_t clock1,clock_t clock2) { double diffticks=clock1-clock2; double diffms=(diffticks)/(CLOCKS_PER_SEC); return diffms; } However this always returns 0 seconds... Is there another method that will work? Also, this is in Linux. Thanks!

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  • Call iconv from Ruby through system()

    - by Sebastian
    I have a problem with iconv tool. I try to call it from rake file in that way: Dir.glob("*.txt") do |file| system("iconv -f UTF-8 -t 'ASCII//TRANSLIT' #{ file } >> ascii_#{ file }") end But one file is converted partly (size of partialy converted: 10059092 bytes, before convertion: 10081854). Comparing this two files prove that not all content was writen to ASCII. When I call this command explicit from shell it works perfectly. Other smaller files are converted without problems. Is there any limitations on iconv or Ruby's system()?

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  • PHP exec() and system() functions always return false in IIS

    - by Loftx
    Hi there, I'm trying to use the PHP exec() or system() (or any other similar function) to run a batch file, but I can't seem to get these to return anything. The simplest example I've seen is this, which outputs nothing: <?php echo system('dir'); ?> The script is running on a windows XP machine on IIS with PHP installed and I've also tried it on my shared hosting account running windows 2003 server/IIS. Can anyone suggest what I need to do to get this working, or provide any commands I can use for troubleshooting? Cheers, Tom

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  • How to detect pending system shutdown on Linux?

    - by Rajorshi
    Hi, I am working on an app where I need to detect system shutdown. However, I have not found any reliable way get a notification on this event. I know that on shutdown, my app will receive a SIGTERM signal followed by a SIGKILL. What I want to know is if there is someway to query if a SIGTERM is part of a shutdown sequence? Does any one know if there is a way to query that programmatically (C API)? As far as I know, the system does not provide any other method to query for an impending shutdowm. If it does, that would solve my problem as well. I have been trying out runlevels as well, but change in runlevels seem to be instantaneous and without any prior warnings.

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  • Issuing native system commands in Scala

    - by Tony
    I want to issue a native system command from a Scala program, and perhaps trap the output. ("ls" comes to mind. There may be other ways to get directory information without issuing the command, but that's beside the point of my question.) It would correspond to os.system(...) in Python. I've looked in "Programming in Scala". I've looked in O'Reilly's "Programming Scala". I've Googled several combinations of terms. No luck yet. Can someone out there give me an example, or point me at a resource where I can find an example?

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  • Killing a script launched in a Process via os.system()

    - by L.J.
    I have a python script which launches several processes. Each process basically just calls a shell script: from multiprocessing import Process import os import logging def thread_method(n = 4): global logger command = "~/Scripts/run.sh " + str(n) + " >> /var/log/mylog.log" if (debug): logger.debug(command) os.system(command) I launch several of these threads, which are meant to run in the background. I want to have a timeout on these threads, such that if it exceeds the timeout, they are killed: t = [] for x in range(10): try: t.append(Process(target=thread_method, args=(x,) ) ) t[-1].start() except Exception as e: logger.error("Error: unable to start thread") logger.error("Error message: " + str(e)) logger.info("Waiting up to 60 seconds to allow threads to finish") t[0].join(60) for n in range(len(t)): if t[n].is_alive(): logger.info(str(n) + " is still alive after 60 seconds, forcibly terminating") t[n].terminate() The problem is that calling terminate() on the process threads isn't killing the launched run.sh script - it continues running in the background until I either force kill it from the command line, or it finishes internally. Is there a way to have terminate also kill the subshell created by os.system()?

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  • System.Net.WebClient Class in .Net CompactFramework 3.5 ?

    - by Leen15
    Hi at all! I need to comunicate with a Server that give me async answers (streamer connection). I find this: http://msdn.microsoft.com/en-en/library/ms144211%28v=VS.80%29.aspx that generate this event: http://msdn.microsoft.com/en-en/library/system.net.webclient.openreadcompleted%28v=VS.80%29.aspx I think this is what i need, but i don't have the WebClient class in my System.Net of CompactFramework 3.5. How can i do? Thanks. EDIT: I've done a more clear question: httpRequest, httpResponse, send GET through Stream and Receive the Result in C#

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  • pthreads recursively calling system command and segfault appears

    - by jess
    I have a code base where i am creating 8 threads and each thread just calls system command to display date in a continuous cycle, as shown below: void * system_thread(void *arg) { int cpu = (int)arg; printf("thread : start %d\n", cpu); for (;;) { // date ã³ãã³ãã®å®è¡ if (mode == 0) { system("date"); } else { f_hfp_nlc_Fsystem("date"); } } sleep(timerval); return NULL; } This application segfaults after running for 2-3 seconds, due to following 2 reasons: 1. read access, where the address is out of VM area 2. write acces, where it does not of write permission and its trying to modify some structure.

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  • Getting input in system() function (Mac)

    - by Alex
    #include <iostream> using namespace std; int main() { short int enterVal; cout << "enter a number to say: " << endl; cin >> enterVal; system("say "%d"") << enterVal; return 0; } Is what I am currently trying. I want the user to enter a number and the system() function says it basically. The code above has an error which says " 'd' was not declared in this scope ". Thanks in advance.

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  • Creating an email notification system based on polling database rows

    - by Ashish Sharma
    I have to design an email notification system based on the following requirements: The email notifications would be created based on polling rows in a Mysql 5.5 DB table when they are in a particular 'Completed' state. The email notification should be sent out in no more than 5 minutes from the time the row was created in the DB table (At the time of DB table row creation the state of the row might not be 'Completed'). Once 5 minutes for the DB table row expire in reaching the 'Completed' state, separate email notification need to be sent (basically telling the user that the original email notification would be delayed) and then sending the email notification as and when the row state reaches to being 'Completed'. The rest of the system requirements are : Adding relevant checks to monitor the whole system via MBeans interface. The system should be scalable so that if the rate of DB table rows creation increases so does the Email notification system be able to ramp up. So I request suggestions on following lines: What approach should I take in solving the problem described from a programming/Design pattern point of view? Suggestion for any third party plugin/software that can be used to solve the problem described? Points to take care regarding scalability and monitoring the health of the system? Java is the language of preference but I am open to using off the shelf components that can be interfaced with Java language or provide standard ports for communication. Currently I do have an in house grown system (written in Java) that is catering to the specified requirements, but it's now crumbling under increased load and now I want to give the problem a fresh look. thanks in advance Ashish

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  • When Do OS Questions Belong on Hardware Service Requests?

    - by Get Proactive Customer Adoption Team
    Untitled Document My Oracle Support—Logging an Operating System Service Request One of the concerns we hear from our customers with Premier Support for Systems is that they have difficulty logging a Service Request (SR) for an operating system issue. Because Premier Support for Systems includes support for the hardware and the associated operating system, you log any operating system issues through a hardware Service Request. To create a hardware Service Request, you enter the information into the Hardware tab of the Create Service Request screen, but to ensure that the hardware Service Request you enter is recognized and routed appropriately for an operating system issue, you need to change the product from your specific hardware to the operating system that the hardware is running. The example below shows you how to create a Service Request for the operating system when the support level is Premier Support for Systems. The key to success is remembering that the operating system coverage is part of the hardware support. To begin, from anywhere within My Oracle Support, click on the Create SR button as you would to log any SR: Enter your Problem Summary and the Problem Description Next, click on the Hardware tab. Enter the System Serial Number (in this case “12345”) and click on Validate Serial Number: Notice that the product name for the hardware indicates “Sunfire T2000 Server” with an option for a drop down List of Values. Click on the product drop down and choose the correct operating system from the list. In this case I have chosen “OpenSolaris Operating System” Next, you will need to enter the correct operating system version: At this point, you may proceed to complete and submit the Service Request. If your company has Premier Support for Systems, just remember that your operating system has coverage under the hardware it runs on, so start with a Hardware tab on the Service Request screen and change the product related information to reflect the operating system you need help with. Following these simple steps will ensure that the system assigns your Service Request to the right support team for an operating system issue and the support engineer can quickly begin working your issue.

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  • Add physical disk to KVM virtual machine

    - by evan
    I'm setting up a file server (nas4free) as a KVM virtual machine on a Ubuntu Server 12.04 system. How do I add physical hard drives directly to the VM so they can be used by the guest (nas4free), but not the host? Specifically the hard drive I'd like to mount is /dev/sda (which is not currently mounted on the server.) So far I've found two solutions but I haven't gotten either to work. The first is from Server Fault where it's suggested to use virt-manager. I haven't gotent this to work because when I try to select an existing drive nothing is being listed. My best guess as to why this is, is because I'm using virt-manager over ssh and not connecting as root, should that make a difference? The second solution I've found here is to just run the command (modified for my system) qm set nas4free -virtio /dev/sda but that seems to require proxmox which I don't have installed and doesn't seem to be in the default repositories? Finally, once the above is sorted out and I can mount the drive directly to the VM, does anyone have an experience with whether the drive should be mounted to the VM as scsi, ide, or virtio? (I know virtio was recommend in the linked ServerFault page, but I hadn't heard of it before now since I mainly use VMWare). Thanks for your help!!!

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  • How do I implement the bg, &, and fg commands functionaliity in my custom unix shell program written in C

    - by user1631009
    I am extending the functionality of a custom unix shell which I wrote as part of my lab assignment. It currently supports all commands through execvp calls, in-built commands like pwd, cd, history, echo and export, and also redirection and pipes. Now I wanted to add support for running a command in background e.g. $ls -la& I also want to implement bg and fg job control commands. I know this can be achieved if I execute the command by forking a new child process and not waiting for it in the parent process. But how do I again bring this command to foreground using fg? I have the idea of entering each background command in a list assigning each of them a serial number. But I don't know how do I make the processes execute in the background, then bring them back to foreground. I guess wait() and waitpid() system calls would come handy but I am not that comfortable with them. I tried reading the man pages but still am in the dark. Can someone please explain in a layman's language how to achieve this in UNIX system programming? And does it have something to do with SIGCONT and SIGSTP signals?

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  • Bootloader error Ubuntu 12.04, system goes to Grub-rescue instead of booting

    - by user83508
    I am trying to install ubuntu 12.04 on my system but it is constantly giving me bootloader install fail error. I have tried to lot to solve this issue but reading articles over the internet but still no gain. Firstly since the bootloader was not getting installed I tried to install it on all the alternative paths given in the installer, failing with I selected install ubuntu without bootloader. Then I tried to manually install bootloader via terminal at try ubuntu via grub-install, but I was not able to do that. Then I tried using boot-repair and it was also not able to install the bootloader because after it my system shows grub-rescue. I tried to use boot-repair and install bootloader on a seperate partition mounted to /boot and still my system is booting and it still shows grub-rescue. The error which my system shows during boot is: Error : no such device : 04ac0510-bd4f-43b8-b885-b885-11c4dec21db8 I am not dual booting and ubuntu is the only OS I am installing. I am using Raid 0 with two blue western digital hard drive so I am not sure whether it is right or not. The details given by boot-repair are in the below mentioned link; http://paste.ubuntu.com/1147208/ Afterwards, I made one more change I installed ubuntu again and this time I installed the bootloader at a different partition on /boot. After this the bootloader error has gone but I am still not able to boot to ubuntu as I get the same error I was getting before. I have not installed dmraid, I feel it is neccessary for Raid0, but I thought ubuntu already has Raid drivers. Moreover in the dmraid installation instructions for 12.04, I used the one for 10.04 and selected to install bootloader at the partitions from the dropdown. This time the installation finished normally without an error but still I am not able to boot my system as the same error shows during booting this time also. Now I am stucked and I have no clue on how I can boot my system. Please tell me how can I boot my system.

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  • How do I implement the bg, &, and bg commands functionaliity in my custom unix shell program written in C

    - by user1631009
    I am trying to extend the functionality of my custom unix shell which I earlier wrote as part of my lab assignment. It currently supports all commands through execvp calls, in-built commands like pwd, cd, history, echo and export, and also redirection and pipes. Now I wanted to add the support for running a command in background e.g. $ls -la& Now I also want to implement bg and fg job control commands. I know this can be achieved if I execute the command by forking a new child process and not waiting for it in the parent process. But how do I again bring this command to foreground using fg? I have the idea of entering each background command in a list assigning each of them a serial number. But I don't know how do I make the processes execute in the background, then bring them back to foreground. I guess wait() and waitpid() system calls would come handy but I am not that comfortable with them. I tried reading the man pages but still am in the dark. Can someone please explain in a layman's language how to achieve this in UNIX system programming? And does it have something to do with SIGCONT and SIGSTP signals?

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  • chromium-browser usus 99,99% IO disk

    - by lars
    My favorite browser: chromium is testing my patience. For some reason it sometimes uses 99,99% of I/O. (reading 2-3MB/s) Other processes (updatedb.mlocate, [kswapd0], clementine, compiz) show the same behavior. However this problem always starts and ends with chromium. To illustrate the impact on my system: when my disk starts to spin like crazy en the led burns continiously the system is so slow that it takes about two to five minuits to switch to tty6, log in and execute "killall chromiumbrowser && killall chromium" This is way faster than starting a new terminal in X, just starting a terminal seems to heavy for compiz under these circumstances. Waiting until its over takes more than 30 minuits, if it ends at all. The exact circumstances are difficult to replicate. Several tabs have to be open, usualy 8 or more. It seems that the chance to increases when more complex sites like gmail of plugins like flash are running. Opening several new tabs at omgubunt.co.uk has the best chance to replecate this isue. I have no idea where to start looking for a solution. Any help would be greatly apreciated ubuntu 12.10 | 2GB | 2x 1.66GHz Intel | 32bit | IBM Thinkpad R60e

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  • How to install Ubuntu 13.10 on Hybrid Disk alongside Windows 8.1

    - by user205691
    I am having trouble installing Ubuntu 13.10 on HP Envy 4-1046tx ultrabook. When i bought this, it came with windows 7 pre-installed, but i upgraded it to 8 and now recently to 8.1. But somehow, i feel 8.1 is slower or something went wrong with the upgrade and made my system slow. I want to try Dual booting Ubuntu 13.10 with windows 8.1 The system recovery drive has windows 7 recovery files. SSD has 4GB allocated to windows 8 (i think for hibernation/rapid start). 25GB of SSD is free and i want to install ubuntu on this SSD pointing it to "/" I will also shrink the windows partition (the only other partition available apart from recovery & SSD) to free up 100GB and allocate this space to "/home" during ubuntu installation. I tried the above steps while on windows 8, but not successful. Ubuntu installation went fine, but the grub was not loaded. I tried to deploy linux via EasyBCD, but after that also, selecting linux in the boot would load grub on command prompt and do nothing. While ubuntu installation, i also deleted the raid drivers with sudo dmraid -rE, but still ubuntu didnt recognize my windows. I think i am missing some steps, so this time i want to do it right with proper info before starting the process. My requirements: dual boot Ubuntu with windows 8.1 c:\ shrinked windows with 300GB on sda1, 100GB for /home on sda1 & ubuntu installed on 25GB SSD volume sda2 (this is mSata i think) GRUB or EFI that helps me load both OS properly without breaking anything SWAP partition can be added if needed on sda1 (4gb?)? I have backed up my drive and have a 16GB usb3.0 with ubuntu loaded. I hope i have mentioned everything i need and know.. All i need now is some guidance and what to do right so that this installation goes as planned :)

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  • System testing - making sure the system conforms to specification. Validation?

    - by user970696
    After weeks of research I have nearly completed my thesis, yet I am unable to clear up my confusion contained in all previous threads here (and in many books): During system testing, we check the system function against system analysis (functional system design) - but that would fit to a definition of verification according to many books. But I follow ISO12207, which considers all testing as validation (making sure work product meets requirement for intended use). How can I justify that unit testing or system testing is validation, even though when I check it against specification? Which fullfils the definiton of verification? When testing that e.g. "Save button" works, is it validation? This picture shows my understanding of V&V, so different from many other sources, including ISTQB etc. Essential problem I have is that a book using the same picture also states on another place that: test activities in the area of validation are usability, alpha and beta testing. For verification, testable system requirements are defined whose correct implementation can be tested through system tests. Isn't that the opposite of what the picture says? Most books present the following picture, where validation is just making sure that customer needs are satisfied. Mind you that according to ISO, validation activity is testing.

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  • Web migration of a VB6 system with VWG

    - by Webgui
    Brinks Bolivia eSAC System (Customer Service) allows to register all different kinds of contacts for a customer; addition to maintaining an updated status of each service or customer request, to have accurate information and perform the appropriate procedures for all applications. The system was originally developed in VB6 and since web access was essential it was offered via Citrix. Since the application's performance was a critical issue as well as the need to offer the system without specific installations the company looked for a solution that would solve those drawbacks of using Citrix. Searching for a solution that would allow it to offer the eSAC system over the web without the need for specific client installations and provide sufficient performance levels even when there is limited bandwidth lead Brinks to a decision to migrate their VB6 Customer Service system to to Visual WebGui. "Developing on Visual WebGui we were able to migrate the system to web environment and even add new features in less time which allows us to offer it over a standard web browser with better performance and no installations as was required with Citrix," concluded Alexander Cuellar. The full article and screenshots of the system are available here.

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  • Run Win7 Guest (raw disk) in Ubuntu (which was installed as Dual Boot on existing Win7)

    - by kingdango
    I installed Ubuntu 12.10 on top of Win 7 as a dual boot (awesome!). I'm hoping to use VirtualBox to run my original Win7 instance as a guest OS under Ubuntu. I found this existing question and followed the directions to no avail. I can get the VMDK file created but when I run it I just get a blank black screen with no additional information and Windows never loads. I see no HD activity or anything that would indicate it's loading. I used this command to create the VMDK file: VBoxManager internalcommands createrawvmdk -filename ~/.VirtualBox/Win7Native.vmdk -rawdisk /dev/sda3 It looks like everything was created correctly but I just get a blank screen when I run the VM. I do get this warning when I boot the VM: VirtualBox - Warning The virtual machine execution may run into and error condition as described below... The medium '/home/XXX/.VirtualBox/Win7Native.vmdk' has a logical size of 583GB but the file system the medium is located on can only handle up to 16GB in theory. We strongly recommend to put all your virtual disk images and the snapshot folder on a proper file system (e.g. etc3) with a sufficient size. ErrorId: Fat Partition Detected Severity: Warning How can I get this working?

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  • Can't start system due to mdadm failing

    - by user101212
    I used to have a 5-disk RAID5 partition, all working very well. I have then decided to add 3 more disks on it, totaling 8 equal disks. I've opened Webmin and just asked to add the disks. Then I've realized the three disks had NTFS partitions, wich mdadm didn't complain, so I tried to stop the growing to remove the Windows partitions. I've tried to remove a disk using the same Webmin, but (as you might guess and call me fool...), the system became unstable. By restarting the system, I've started receiving these messages: "udev[126]: timeout: killing '/sbin/mdadm --incremental /dev/sdh1' [311]" "udev[124]: timeout: killing '/sbin/mdadm --detail --export /dev/md0' [316]" I've formated the system disk, hoping to get a system up and running. I did that with all RAID disks disconected, so everything was fine. I then reconnected the disks, wich was also ok. And finally installed mdadm using apt-get. By reboot, the system has found the mdadm intention of growing the system, so the same messages appear again. I other words: I can't even reach a command prompt to do something. Any ideas of what to do? I believe I could turn off the system, disconnect the disks and look for the mdadm.conf file. Would that be a good idead? I'm no Linux expert, so I'm really lost here.

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