How to get logs of a specific time range on Linux?

ByEric Ma

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…

How to monitor temperatures of laptop on Linux

ByEric Ma

How to monitor temperatures of laptop on Linux? This works on Linux Mint: sudo aptitude install lm-sensors hddtemp For lm-sensors, first detect the sensors by: sudo sensors-detect To detect the temperature in the system: sudo sensors To detect the HDD (e.g. sda) temperature: sudo hddtemp /dev/sda An example of the output: [zma@mini:~]$ sudo sensors acpitz-virtual-0…

How to boot Linux Mint to the console by default?

ByEric Ma

How to boot Linux Mint to the console by default? (that is, the run level 3). 2 methods introduced here to boot Linux Mint to console/command line. Method 1 (may only work for earlier releases; check method 2 below): set kernel option. Edit /etc/default/grub and add text to GRUB_CMDLINE_LINUX_DEFAULT: GRUB_CMDLINE_LINUX_DEFAULT=”quiet splash text” Then, re-generate grub…

How to turn a BIOS-based Linux Mint 17 installation to UEFI booting?

ByEric Ma

I installed Linux Mint 17 in the traditional BIOS mode. However, Windows 8.1 on my computer can only boot in the UEFI mode. I do not want to reinstall the Windows or erase it. How to turn a BIOS-based Linux Mint 17 installation to UEFI booting? You may refer https://help.ubuntu.com/community/UEFIBooting for some information.

Finding Which Package Provides a File in Ubuntu Linux and Linux Mint

ByEric Ma

How to find which package provides a file in Debian based releases, such as Linux Mint, Ubuntu? You can use `dpkg`: $ dpkg -S /path/to/the/file -S or –search is the option to make dpkg do a “search”: -S, –search filename-search-pattern… Search for a filename from installed packages. To search which package provides a command file…

How to set the number of mappers and reducers of Hadoop in command line?

ByEric Ma

How to set the number of mappers and reducers of Hadoop in command line? Number of mappers and reducers can be set like (5 mappers, 2 reducers): -D mapred.map.tasks=5 -D mapred.reduce.tasks=2 in the command line. In the code, one can configure JobConf variables. job.setNumMapTasks(5); // 5 mappers job.setNumReduceTasks(2); // 2 reducers Note that on Hadoop…

Filter away non-printable ASCII characters on Linux?

ByEric Ma

Sometimes the commands’ output have some non-printable ASCII characters. How to filter away these non-printable ASCII characters on Linux? You can consider the problem as “how to leave only printable ascii characters?”. The printable characters in ASCII table are: Octal 011: Tab Octal 012: Line Feed Octal 015: Carriage Return Octal 040 to 176: printable…

How to calculate the average of value in lines of a text file on Linux by a script?

ByEric Ma

How to calculate the average of value in lines of a text file on Linux by a script? The file.txt is like: Run 0: Time used: 22.235331711 seconds. Run 1: Time used: 20.784491219 seconds. Run 2: Time used: 21.851638876 seconds. What I want it to calculate the average time. awk is handy for this purpose:…

How to install multiple versions of sbt on my Linux host?

ByEric Ma

How to install multiple versions of sbt on my Linux host For example, some projects use 0.12.x while some use 0.13.x. Installing neither in the system only is not sufficient enough. You may use the excellent sbt-extras: https://github.com/paulp/sbt-extras Most of the time, it detects the version of sbt needed in the project direoctory automatically: [zma@office…

How to package a Scala project to a .jar with sbt?

ByEric Ma

How to package a Scala project to a .jar file with sbt? Manually packaging the .class files are fine but too tedious. A jar of just the project classes The command: sbt package will produces the main artifact as a jar into target/scala-2.x.y/project_name_2.x.y-zz.jar. Continuously building the package: sbt ~package Standalone jar with all dependencies If…