If you install libvirt from ubuntu software library like this sudo apt-get install libvirt-bin The default version is 1.2.2 for Ubuntu Trusty. However, after you upgrade it to version 2.5.0 from its source codes (restart the libvirtd service), you will see following error if you want to install vm with virt-install. # ./installkvm1.sh Starting install…
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Category: Tutorial
What is the vruntime of one process after it is moved into another run queue in Linux Kernel
Posted onWhen we do migration, one process will be migrated from one source CPU’s runqueue to destination CPU’s run queue. What is the virtual run time (if CFS is used) after it is moved into destination CPU’s run queue? When the process is dequeued from source CPU’s run queue, its vruntime will minus the minimum vruntime
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How to use ioprio_set in linux c
Posted onSince there is no glibc wrapper for ioprio_set in linux c, we need to call this API with some definition. Using syscall in linux as follows. syscall(SYS_ioprio_set, IOPRIO_WHO_PROCESS, pid, IOPRIO_PRIO_CLASS(IOPRIO_CLASS_IDLE)); Some other definitions to declare above macros. 69 enum { 70 IOPRIO_CLASS_NONE, 71 IOPRIO_CLASS_RT, 72 IOPRIO_CLASS_BE, 73 IOPRIO_CLASS_IDLE, 74 }; 75 76 enum { 77
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How to install encfs on CentOS 6?
Posted onI noticed your answer on configuring encfs on CentOS 6. I had difficulties installing encfs on CentOS 6. How did you install it? Thanks. For CentOS 6, I used a slightly old version (version 1.7.4) using an RPM built for by PUIAS: For x86-64 version: # yum install http://puias.princeton.edu/data/puias/6/x86_64/os/Addons/fuse-encfs-1.7.4-1.puias6.x86_64.rpm For i686 version: # yum install
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Where to download an old release package of Hadoop?
Posted onThe download page of Hadoop http://hadoop.apache.org/releases.html only contains several recent release packages. I would like to download some old release packages such as Hadoop 2.5.0 which is not available anymore on the release page. Where to download a copy of the old release? You can download the old release packages of Hadoop on the http://archive.apache.org
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Cannot start VM with error “no network with matching name ‘default'”
Posted onI update libvirt version and want to start VM with the new libvirt tools but I failed as follows. > sudo virsh start kvm1 error: Failed to start domain kvm1 error: Network not found: no network with matching name ‘default’ It seems that the default ‘virbr0’ is missing after I update libvirt so I solve
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How to install Tex Live on CentOS 7 Linux?
Posted onThe LaTex packages in CentOS 7 Linux is not sufficient enough. I would like to Install Tex Live such as Tex Live 2016. How could I install it on CentOS 7? The best way I found is to use the texlive offical installation tool to install the full packages for texlive 2016. It will take
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Extract Images from a PDF File in Linux
Posted onHow to extract the images from a PDF file in Linux? You may use the pdfimages tool. To output jpg images from a PDF ./a.pdf, run pdfimages -j ./a.pdf ./images ./images is the output images’ prefix. The images in ./a.pdf will be extracted and saved as ./images-nnn.jpg. -j options make pdfimages generate JPEG files.
How to output function stack in Linux Kernel
Posted onIn Linux Kernel, we usually trace/debug what kind of events will trigger the phenomena we find in the system. For example, what kind of event will trigger the fact that the timeslice of one process will be very short. In order to solve these kind of problems, we need to output the function stack. Currently,
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encfs on CentOS 6 can’t mount as normal user
Posted onOn CentOS 7, using a normal user, encfs works just well. On CentOS 6, using the root user, encfs works. However, the problem is, on CentOS 6, using a normal user account, encfs does not work as on CentOS 7. $ encfs -s ~/t/.enc ~/t/enc EncFS Password: fuse: failed to exec fusermount: Permission denied fuse
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What’s the difference between memory coherence and consistency?
Posted onIn memory hierarchical, it needs to be coherence and consistency. However, they are different things. What are the differences? Memory coherence: a memory system is coherent if any read of a data item returns the most recently written value of that data item (what values can be returned by a read). Memory consistency: A memory
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How to install dia on CentOS 7 Linux?
Posted onDia seems not available in the official repository of CentOS 7. How to install dia on CentOS 7 Linux? You can find built dia packages in some additional repositories for CentOS. First, enable EPEL following this link. Second, enable Nux Desktop following this link. Then, you can install dia by # yum install dia
In Bash script, how to join multiple lines from a file?
Posted onIn Bash script, how to join multiple lines from a file? For example, to join the lines a good boy to a good boy You can use tr command, something like: tr -s ‘n’ ‘ ‘ < file.txt It just goes through its input and makes changes according to what you specify in two sets
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Ubuntu’s GUI response is very slow
Posted onFor Dell PowerEdge T630 server, if you install latest Ubuntu desktop version (16.04) or (14.04), you will get a very slow GUI (X-window). $ inxi -G Graphics: Card: Matrox Systems G200eR2 X.org: 1.15.1 driver: vesa tty size: 205×58 Advanced Data: N/A out of X For Ubuntu 14.04.1, this problem can be solved by following steps.
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How to remove the bottom panel in gnome 3 classic?
Posted onThe gnome 3 classic’s bottom panel looks not useful to me. I do not use it. How to remove the bottom panel in gnome 3 classic? That bottom panel is from the “Window List” plugin. The gnome 3 classic package depends on that plugin package on CentOS 7 as far as I checked. And Gnome
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How to redirect non-www domain to www domain in .htaccess?
Posted onI have a website. But I would like use the www.example.com instead of example.com. How to redirect non-www domain to www domain on my server? I am using apache2 (httpd). You can add a piece of code into the top .htaccess in your site: Specific method: redirect example.com domain to www.example.com domain RewriteEngine On RewriteBase
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How to make output jpeg file of xsane smaller on Linux?
Posted onxsane’s output jpeg file is large (10+MB). But we usually do not need it to make a so big jpeg file. Some compression (even lossy) will be good. How to make output jpeg file of xsane smaller on Linux? You can adjust the output file size by changing the compression levels and quality. Through the
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How to save the output of screen windows to a file on Linux?
Posted onIn the screen, copying the history of the window output is quite hard. How to save the screen easily to a file? First type Ctrl + A then : to get to command mode. In the command mode, execute hardcopy -h /path/to/file screen will save the window output to /path/to/file.
How to detect whether a file is readable and writable in Python?
Posted onBefore reading or writing a file, access should be checked first. How to detect whether a file is readable and writable in Python? You can use the os.access(path, mode) library function https://docs.python.org/release/2.6.6/library/os.html#os.access like the Linux access library function for C. It returns True if access is allowed, False if not. For readable and writable, you
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How to set up HP printer and scaner on CentOS 7?
Posted onHow to set up the driver for an HP all-in-one printer/scanner on CentOS 7 Linux? First, install these packages and it may ask you to download and install other plugins. Without these packages, my printer does work. # yum install hplip hplip-gui hpijs Second, install plugins for the HP printer. # hp-plugin Then you can
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