Linux Notes and Tips

linux_notes.md

Linux Notes

Remove unused Kernels and packages in Ubuntu

$ sudo apt-get remove --purge $(dpkg -l 'linux-*' | sed '/^ii/!d;/'"$(uname -r | sed "s/\(.*\)-\([^0-9]\+\)/\1/")"'/d;s/^[^ ]* [^ ]* \([^ ]*\).*/\1/;/[0-9]/!d')

Show the size of the current directory

$ du -ch | grep total

Execute sshuttle (from root user)

$ sshuttle -r tunnel.cloudfed.biz 0/0 -v --dns -D --pidfile /var/run/sshuttle.pid -x 10.95.21.0/24 -x 10.212.0.0/16 -x 172.17.0.0/16

Check the External IP

$ curl http://myexternalip.com/raw

Ubuntu 14.04 - Remove online search

$ gsettings set com.canonical.Unity.Lenses remote-content-search ‘none’

Manage java installations

In .bashrc file add the following lines to export the JAVA_HOME from the java alternatives:

# JAVA
JAVA_SUFFIX=/bin/java
CURRENT_JAVA=`readlink /etc/alternatives/java`
export JAVA_HOME=${CURRENT_JAVA%$JAVA_SUFFIX}

Create a simple script to switch JRE in Java Alternatives. Give the name switch_jre

#!/bin/bash

JDK5=/home/luca/tools/java/jdk1.5.0_22/jre
JDK6=/home/luca/tools/java/jdk1.6.0_45/jre
JDK7=/home/luca/tools/java/jdk1.7.0_80/jre
JDK8=/home/luca/tools/java/jdk1.8.0_91/jre


sudo rm /etc/alternatives/java

case "$1" in
        "5")
                export JAVA_HOME=$JDK5
                sudo ln -s "$JDK5/bin/java" /etc/alternatives/java
                ;;
        "6")
                export JAVA_HOME=$JDK6
                sudo ln -s "$JDK6/bin/java" /etc/alternatives/java
                ;;
        "7")
                export JAVA_HOME=$JDK7
                sudo ln -s "$JDK7/bin/java" /etc/alternatives/java
                ;;
        "8")
                export JAVA_HOME=$JDK8
                sudo ln -s "$JDK8/bin/java" /etc/alternatives/java
                ;;
        *)
                echo "Unknown JDK version!"
                ;;
esac
export JDK_HOME=$JAVA_HOME

echo "Calling 'java' to output the currently used java version"
java -version

Use the script as

$ switch_jre 8 #to choose java 8