How to install node.js on Ubuntu/Linux Mint?
How to install node.js on Ubuntu/Linux Mint? This is how I install node.js on Linux Mint: # aptitude install nodejs nodejs-legacy npm The nodejs-legacy makes sure the command node will invoke node.js.
Tutorial
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How to run gitbook on a headless server (make Calibre run in headless server)?
When use gitbook to generate ebook, Calibre reports this: RuntimeError: X server required. If you are running on a headless machine, use xvfb After xvfb is installed, it does not work either. How to make gitbook/Calibre work on a headless server? You need to wrap the command ebook-convert with xvfb-run. However, in gitbook (lib/generate/ebook/index.js), ebook-convert…
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How to install node.js on Fedora?
How to install node.js on Fedora? You may install it by: # yum install nodejs npm
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How to config network in host (wireless network) for QEMU guest os
The host os is connected into network by wireless one so how to let its guest os connect network. Take [1] as a reference. I run it successfully with following steps. 1, create /etc/qemu-ifup script and chmod it. 2, start a qemu guest os with command sudo ./qemu/qemu-system-x86_64 -enable-kvm -m 1024 -drive file=marss_dram.qcow2 -vnc 127.0.0.1:0…
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How to find the DataNodes that actually store a file in HDFS?
A file may be splitted to many chunks and replications stored on many datanodes in HDFS. Now, the question is how to find the DataNodes that actually store a file in HDFS? You may use the dfsadmin -fsck tool from the Hadoop hdfs util. Here is an example: $ hadoop fsck /user/aaa/file.name -files -locations -blocks…
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kernel netfront: Too many frags in Xen VM
We set up Xen F19 VMs on a Xen 3.4.3 / 2.6.32.13 xenified kernel. Check here.). However, we find the Xen VM keeps reporting: kernel netfront: Too many frags and skb rides the rocket in the dmsg. This solves the problem (assume in physical server vif1.0 is for the eth0 on the VM): On the…
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How to increase the number of files allowed to be opened on Linux?
On my system: $ ulimit -n 1024 Some tools like GATK are aggressive in creating temporary files by creating more than 1000 files under /tmp/. This will cause the program to fail. How to increase the number of files allowed to be opened on Linux? To increase the max number of open files to 10240,…
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How to write /etc/fstab entry for –bind mounting?
How to write /etc/fstab entry for –bind mounting like mount –bind /home/hadoop/hdfs/store-tmp /home/store/tmp From man 8 mount: Since Linux 2.4.0 it is possible to remount part of the file hierarchy somewhere else. The call is mount –bind olddir newdir or shortoption mount -B olddir newdir or fstab entry is: /olddir /newdir none bind
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How to change number of replications of certain files in HDFS?
The HDFS has a configuration in hdfs-site.xml to set the global replication number of blocks with the “dfs.replication” property. However, there are some “hot” files that are access by many nodes. How to increase the number of blocks for these certain files in HDFS? You can the replication number of certain file to 10: hdfs…
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How to get logs of a specific time range on Linux?
The logs I am processing is Hadoop log (log4j). It is in format like: 2014-09-20 21:55:11,855 INFO org.apache.hadoop.nfs.nfs3.IdUserGroup: Updated user map size: 36 2014-09-20 21:55:11,863 INFO org.apache.hadoop.nfs.nfs3.IdUserGroup: Updated group map size: 55 2014-09-20 22:10:11,907 INFO org.apache.hadoop.nfs.nfs3.IdUserGroup: Update cache now 2014-09-20 22:10:11,907 INFO org.apache.hadoop.nfs.nfs3.IdUserGroup: Not doing static UID/GID mapping because ‘/etc/nfs.map’ does not exist. Now, I…
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What’s the difference between Reliability, Durability, and Availability for data storage system?
Some important concepts in distributed system like Hadoop distributed file system, Google file system and so on. Answer from http://www.quora.com/Whats-the-difference-between-Reliability-Durability-and-Availability-for-data-storage-system The difference between durability and availability is fairly simple. Durability is about what happens when all power goes out everywhere. Has all data been written to stable storage that doesn’t require power (e.g. disk/flash), in…
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How to read email in Maildir on Linux?
How to read email in Maildir on Linux? You can use mutt by: mutt -f /path/to/mail/dir/
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if (p:string list) = c (is the only element)
if (p:string list) = [c] then (divide p1 c) showing unbound value c. i want to equalise (if one element in p which is (c:anything)) and use that variable let p = [“ocaml”] let f s = match s with | [c] -> print_endline c | _ -> print_endline “ops” f p It will print:…
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Making Hadoop Java process heap larger?
In Hadoop 2.5.0, I use ‘ps -aux’ and find the Java process has options: -Xmx1000m However, my nodes have 32GB memory. How to make Hadoop Java process heap larger? In yarn-env.sh, you can find: # For setting YARN specific HEAP sizes please use this # Parameter and set appropriately # YARN_HEAPSIZE=1000 In hadoop-env.sh, you can…
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How to capture camera photo/video using MPlayer on Linux?
How to capture camera photo/video using MPlayer on Linux? You can watch the video from the camera by MPlayer: # mplayer tv:// Note that you need the root privilege to play the tv://. You can use mplayer to capture photos by: # mplayer -vo png -frames 3 tv:// If will store files 0000000{1..3}.png in the…
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How to view .mbox files on Linux?
How to view .mbox files on Linux? Thunderbird can read mbox files well. You can drop your mbox files to the Local Folders directory of Thunderbird and restart Thunderbird. It will index the emails and show them. To find the Local Folders directory of Thunderbird: Open “Account Settings” and click on “Local Folders” to see…
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How to make Thunderbird check for new messages in all IMAP folders?
How to make Thunderbird check for new messages in all IMAP folders? Under “Edit/Tools > Options > Advanced”, click the “Config Editor” button. In the config editor, set the mail.check_all_imap_folders_for_new configuration to “true“.
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Finding All Available Versions of a Package in Ubuntu
How to find all available versions of a package in Ubuntu? To list available versions of a package: apt-cache showpkg <package-name> For example, to check all versions of thunderbird: $ sudo apt-cache showpkg thunderbird Package: thunderbird Versions: 1:31.1.1+build1-0ubuntu0.14.04.1 (/var/lib/apt/lists/archive.ubuntu.com_ubuntu_dists_trusty-updates_main_binary-amd64_Packages) (/var/lib/apt/lists/security.ubuntu.com_ubuntu_dists_trusty-security_main_binary-amd64_Packages) Description Language: File: /var/lib/apt/lists/archive.ubuntu.com_ubuntu_dists_trusty_main_binary-amd64_Packages MD5: 68ed1001b79d708ad48956a0c129114d Description Language: en File: /var/lib/apt/lists/archive.ubuntu.com_ubuntu_dists_trusty_main_i18n_Translation-en MD5: 68ed1001b79d708ad48956a0c129114d 1:31.0+build1-0ubuntu0.14.04.1 (/var/lib/dpkg/status)…
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How to unlock a locked SSH terminal accidentally by ctrl-s on Linux?
I find I sometimes lock the SSH terminal accidentally by ctrl-s on Linux. How to unlock/unfreeze it? Ctrl-s: lock the SSH terminal. Ctrl-q: unlock the SSH terminal.
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How to find and change a user’s UID on Linux?
How to find and change a user’s UID on Linux? Find the UID of a user: id -u $USER_NAME Change a user’s UID: # usermod -u $NEW_UID $USER_NAME