Questions and answers.
I want to attach a disk to a DomU. The Xen DomU is running and should not be rebooted. Hence, changing its configuration file is not an option. How to dynamically attach a disk to running DomU in Xen? To attach phy:vg_xen/vm-228-large to vm-228 as xvdb, run this on Dom0: # xl block-attach vm-228 phy:vg_xen/vm-228-large…
How to make ctags recognize specific files with certain extensions such as .c0 or .puc as C source files? You may add this line to your ~/.ctags: –langmap=c:+.c0,c:+.puc
How to make taglist recognize specific files with certain extensions as C source files? You may try adding this line to your ~/.vimrc: autocmd BufRead,BufNewFile *.c0 set filetype=c Reference: https://stackoverflow.com/questions/9013263/vim-tagslist-plugin-not-detecting-custom-language-racket
We may need to maintain a dev-name branch on git remote server to share your codes. How to create the branch? 1, git checkout -b your_branch_name 2, Do your changes, add commit 3, git push origin your_branch_name References:http://stackoverflow.com/questions/1519006/how-do-you-create-a-remote-git-branch
Which simple and basic image editors are good on Linux like the paint program on Windows? GIMP is great but too high weighted for normal usage like resizing, cropping, image annotation with text. Pinta is a free and open source drawing/editing program that is easy to edit images. It is available on many Linux distros….
I want to kick off a user such as “bob” on a Linux box which I managed remotely. How to do this? bob may log on the Linux box by various ways: Log on the screen on the Linux box (locally) with a X server. Log on remotely by a ssh shell. Log on by…
How can I force iPhone to reboot/restart/reset when it locks up completely and does not response? To force an iPhone to restart: Press and hold the iPhone’s power key and home button together. Holding the two keys for around 10~15 seconds until the screen is turned off. Release the buttons once the screen lights up…
We have a running HDFS cluster. Currently, the NameNode metadata data directory has only one directory configured in hdfs-site.xml: <property> <name>dfs.namenode.name.dir</name> <value>file:///home/hadoop/hdfs/</value> <description>NameNode directory for namespace and transaction logs storage.</description> </property> We would like to add a new directory for dfs.namenode.name.dir to make replicas of the metadata on a separated disk for higher data reliability….
Resizing images on Linux with gThumb is easy. However, I have a batch of images inside a folder. Manually resizing them will consume too much time. How to automatically resize them on Linux with a script? You can use convert from ImageMagick together with bash script to resize images inside a directory. mkdir resize; IFS=$(echo…
The “Entering/Leaving…” messages when invoking another make by a make is kind of annoying. Is it possible to suppress these messages and how to suppress them? For GNU make, it is controlled by options: -w, –print-directory Print a message containing the working directory before and after other processing. This may be useful for tracking down…
If you encounter an error message like the one below when attempting to SSH to a server: @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ @ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @ @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY! Someone could be eavesdropping on you right now (man-in-the-middle attack)! It is also possible that a host key has…
I noticed that some guys’ screen console has a status bar with tab numbers. That will be very useful for 1) know you are using screen rather than a normal terminal. 2) which tab you are working in. Below is my ~/.screenrc: hardstatus alwayslastline hardstatus string ‘%{= kG}[ %{G}%H %{g}][%= %{=kw}%?%-Lw%?%{r}(%{W}%n*%f%t%?(%u)%?%{r})%{w}%?%+Lw%?%?%= %{g}][%{B}%Y-%m-%d %{W}%c %{g}]’ It…
How to detect whether a .jpg image is almost blank/black on Linux? Here is a bash function that I used to detect whether an image is black on Linux: function isBlank () { mean=`convert $1 -format “%[mean]” info:` echo “$mean” } It uses ImageMagic to generate formatted image characteristics (the mean). If the mean is…
A related question: how to find the replication factors of files in a HDFS cluster? method 1: You can use the HDFS command line to ls the file. The second column of the output will show the replication factor of the file. For example, $ hdfs dfs -ls /usr/GroupStorage/data1/out.txt -rw-r–r– 3 hadoop zma 11906625598 2014-10-22…
How to list all files from a .deb package like rpm -ql on RPM based systems? Use this command dpkg -L pkg_name -L lists files: -L, –listfiles package-name… List files installed to your system from package-name. More on the dpkg command, check dpkg manual.
I have multiple jpg images as files like 001.jpg, 002.jpg … How to merge multiple jpg images to a pdf on Linux? convert is your good friend: convert *.jpg output.pdf
How to remove .svn directories under hlfs dir recursively as follows. weiwei@weiwei-HP-Compaq-dx6128-MT-PX478AV:~/workshop1/hlfs > find ./ -name “.svn” ./test/build/.svn ./test/.svn ./output/conf/.svn ./output/lib32/.svn ./patches/.svn ./src/include/.svn ./src/include/api/.svn ./src/snapshot/.svn ./src/snapshot/unittest/build/.svn ./src/snapshot/unittest/.svn ./src/utils/.svn ./src/clean/Mapreducer/build/.svn ./src/clean/Mapreducer/.svn ./src/clean/.svn ./src/clean/unittest/.svn ./src/icache/.svn ./src/icache/unittest/.svn ./src/backend/.svn ./src/storage/.svn ./src/cache/.svn ./src/cache/unittest/.svn ./src/clone/.svn ./src/tools/.svn ./src/tools/unittest/.svn ./src/logger/.svn weiwei@weiwei-HP-Compaq-dx6128-MT-PX478AV:~/workshop1/hlfs > find ./ -name “.svn” | xargs rm -rf
How to download a rtmp video stream on Linux? You can use mplayer to dump the rtmp stream like: mplayer -dumpstream rtmp://example.com/path/to/stream.mp4 It will generate ./stream.dump and you can rename it to the file with the extension you need like stream.mp4. The rtmp link usually can be found from the HTML or JavaScript source code…
Now, I have a running HDFS cluster storing lost files. I want to change its default replication factor. How to change it? What will happen after it is changed? For example, I change from 2 to 3. Will HDFS automatically re-replicate the data chunks? First, the replication factor is client decided. Second, the replication factor…
What is the design of Snapshots in HDFS? This PDF documents the design of snapshot. Jing Zhao and Tsz-Wo Sze from Hortonworks gave a great talk on the design of HDFS snapshots. The slides can be downloaded at here. The development of snapshot is tracked by HDFS-2802.