Μηνιαία αρχεία: Απρίλιος 2016


HOWTO: Make Terminator Terminal Act Like Guake Terminal in Ubuntu 16.04 LTS (XenialXerus) Desktop edition x64 bit architecture 3

We propose an alternative solution to making terminator act like guake that requires two additional packages: xdotool and wmctrl.

Our proposal will launch terminator if there is not instance running.

In Ubuntu you can install the needed packages from the official repositories using sudo apt-get install xdotool wmctrl.

Using a text editor, create in you home folder a file named nano ~/toggle_visibility.sh and copy there the contents of the following chunk of code. You can also use nano, from a terminal issue nano ~/toggle_visibility.sh, then paste the code and hit CTRL+X to exit. When prompted if you want to save press ‘Y’ and hit enter.

#!/bin/bash

#The purpose of this script is to allow the user to toggle the visibility of (almost) any window.
#Please note it will work on the first match, so if there are multiple instances of an application it would be a random window of them the one to be affected.
#Usually it will control the window with the smallest PID.

#Checking that all dependencies are met, since we cannot proceed without them.
declare -a DEPENDENCIES=("xdotool" "wmctrl");
declare -a MANAGERS=("dnf" "apt-get");

for DEPENDENCY in ${DEPENDENCIES[@]}; do
    echo -n "Checking if $DEPENDENCY is available";
    if hash $DEPENDENCY 2>/dev/null; then
        echo "- OK, Found";
    else
        echo "- ERROR, Not Found in $PATH";
        for MANAGER in ${MANAGERS[@]}; do
            if hash $MANAGER 2>/dev/null; then
                echo -n "$DEPENDENCY is missing, would you like to try and install it via $MANAGER now? [Y/N] (default is Y): ";
                read ANSWER;
                if [[ "$ANSWER" == "Y" || "$ANSWER" == "y" || "$ANSWER" == "" ]]; then
                    sudo "$MANAGER" install "$DEPENDENCY";
                else
                    echo "Terminating";
                    exit -1;
                fi
            fi
        done
    fi
done

APPLICATION="$1";
FULL_COMMAND="$2";

#Checking if the application name provided by the user exists
if ! hash $APPLICATION 2>/dev/null; then
    echo -e "$APPLICATION does not seem to be a valid executable\nTerminating";
    exit -2;
fi

#Checking if the application is running.
PID=$(pgrep -u `whoami` -f "$FULL_COMMAND" | head -n 1);

#If the application is not running, we will try to launch it.
if [ -z $PID ]; then
  echo "$FULL_COMMAND not running, launching it..";
    $FULL_COMMAND;
else
    #Since the application has a live instance, we can proceed with the rest of the code.
    #We will get the PID of the application that is currently focused, if it is not the application we passed as parameter we will change the focus to that. In the other case, we will minimize the application.
  echo -n "$FULL_COMMAND instance found - ";
    FOCUSED=$(xdotool getactivewindow getwindowpid);
    if [[ $PID == $FOCUSED ]]; then
    echo "It was focused so we are minimizing it";
        #We minimize the active window which we know in this case that it is the application we passed as parameter.
        xdotool getactivewindow windowminimize;
    else
    echo "We are setting the focus on it";
        #We set the focus to the application we passed as parameter. If it is minimized it will be raised as well.
        wmctrl -x -R $APPLICATION;
    fi
fi

exit 0

Afterwards, you need to make the script an executable so you should issue chmod +x ~/toggle_visibility.sh to do that.

Then, execute ~/toggle_visibility.sh in your terminal once. We need to do that in order to install any missing dependencies for the tool.

Finally, you need to create a custom shortcut that will call the script using the key combination you like at any point.

To complete the procedure:

  1. Go to ‘System Settings’ either by clicking on the menu on the top right corner that looks like a light bulb or by issuing the following in a terminal unity-control-center to start the unity control center.
  2. In the newly appeared window, click on the ‘keyboard’ icon that is in the category ‘Hardware’.
  3. After that, click on the tab ‘Shortcuts’
  4. and on the left list, click on custom shortcuts.
  5. You will see a button with the + sign right next to the list, click that.
  6. In the dialog box that will appear enter the following:
    – In the name field enter anything you like. e.g ‘Toggle Terminator Visibility’
    – In the command field enter /home/<USER>/toggle_visibility.sh terminator "^/usr/bin/python /usr/bin/terminator$" where <USER> enter your own username.
    – Click apply.
  7. You will see a new row with two columns with the name you just set in the first column. Click on the second column, where it should say ‘Disabled’ and the press the key combination you want for toggling terminator e.g F12

You are ready to go 🙂

Just try the key combination you just provided and terminator will appear in front of you. Pressing it once more it will hide it.

NOTE: Please keep in mind that the above script can be used for other applications as well. In step 7, we gave as parameter the name of the application to be used, if you change that you could use it with other applications like Firefox.


Grep lines that do not begin with ‘#’ or ‘;’

Recently, we wanted to modify  the squid configuration file, which is really really big!

wc -l /etc/squid/squid.conf
7898 /etc/squid/squid.conf

We wanted to find all active rules that are enabled to modify our proxy server. Out of those ~8K lines less than 20 are actually active configuration, the rest is documentation.

To find all active configuration lines we needed to find all lines that:

  • are not empty
  • do not start with #
  • do not start with ;

To do this we used the following grep command

grep "^[^#;]" /etc/squid/squid.conf

The first ^ refers to the beginning of the line, this way if in a line there is some configuration and after that there is a comment it will not be excluded by mistake. The rest, [^#;] matches any character which is not # or ;.

This is what was actually in my configuration file (out of ~8K lines)

acl SSL_ports port 443
acl Safe_ports port 80        # http
acl Safe_ports port 21        # ftp
acl Safe_ports port 443        # https
acl Safe_ports port 70        # gopher
acl Safe_ports port 210        # wais
acl Safe_ports port 1025-65535    # unregistered ports
acl Safe_ports port 280        # http-mgmt
acl Safe_ports port 488        # gss-http
acl Safe_ports port 591        # filemaker
acl Safe_ports port 777        # multiling http
acl CONNECT method CONNECT
http_access deny !Safe_ports
http_access deny CONNECT !SSL_ports
http_access allow localhost manager
http_access deny manager
http_access allow localhost
http_access deny all
http_port 3128
coredump_dir /var/spool/squid
refresh_pattern ^ftp:        1440    20%    10080
refresh_pattern ^gopher:    1440    0%    1440
refresh_pattern -i (/cgi-bin/|\?) 0    0%    0
refresh_pattern (Release|Packages(.gz)*)$      0       20%     2880
refresh_pattern .        0    20%    4320

Copy all databases to another host

The following command will use mysqldump to create a dump of all available databases in the OLD_HOST that are available for the user OLD_USER.
The results will be imported to another server via the mysql pipe.

OLD_USER="myUser"; OLD_PASS="myPASS"; OLD_HOST="myHost";
NEW_USER="myUserNEW"; NEW_PASS="myPASSNEW"; NEW_HOST="myHostNEW";
mysqldump -u "$OLD_USER" -p"$OLD_PASS" -h "$OLD_HOST" --all-databases | mysql -h "$NEW_HOST" -u "$NEW_USER" -p"$NEW_PASS";

The user must have the LOCK TABLES privilege for the above command to work or else you will get the following error.

mysqldump: Got error: 1044: "Access denied for user 'OLD_USER'@'OLD_HOST' to database 'DBNAME'" when using LOCK TABLES

In case you cannot give the privilege to the user, then use the parameter --single-transaction to mitigate the problem. The command changes as follows.

OLD_USER="myUser"; OLD_PASS="myPASS"; OLD_HOST="myHost";
NEW_USER="myUserNEW"; NEW_PASS="myPASSNEW"; NEW_HOST="myHostNEW";
mysqldump -u "$OLD_USER" -p"$OLD_PASS" -h "$OLD_HOST" --single-transaction --all-databases | mysql -h "$NEW_HOST" -u "$NEW_USER" -p"$NEW_PASS";

In case you want to copy only specific databases, use the following

OLD_USER="myUser"; OLD_PASS="myPASS"; OLD_HOST="myHost"; OLD_DBS=("DB1" "DB2");
NEW_USER="myUserNEW"; NEW_PASS="myPASSNEW"; NEW_HOST="myHostNEW";
mysqldump -u "$OLD_USER" -p"$OLD_PASS" -h "$OLD_HOST" "${OLD_DBS[@]}" | mysql -h "$NEW_HOST" -u "$NEW_USER" -p"$NEW_PASS";

In case you want to copy only specific tables from a database, use the following

OLD_USER="myUser"; OLD_PASS="myPASS"; OLD_HOST="myHost"; OLD_DB="DB1"; OLD_TABLES=("TBL1" "TBL2");
NEW_USER="myUserNEW"; NEW_PASS="myPASSNEW"; NEW_HOST="myHostNEW"; NEW_DB="NewDB";
mysqldump -u "$OLD_USER" -p"$OLD_PASS" -h "$OLD_HOST" "$OLD_DB" "${OLD_TABLES[@]}" | mysql -h "$NEW_HOST" -u "$NEW_USER" -p"$NEW_PASS" "$NEW_DB";

Export/Backup all MySQL databases

The following command will use mysqldump to create a dump of all available databases in the HOST that are available for the user USER.
The results will be found in a file that begins with the current date and will contain the hostname as part of the name.

USER="myUser"; PASS="myPASS"; HOST="myHost"; mysqldump -u "$USER" -p"$PASS" -h "$HOST" --all-databases > "`date +%F`-backup-all.$HOST.sql"

The user must have the LOCK TABLES privilege for the above command to work or else you will get the following error.

mysqldump: Got error: 1044: "Access denied for user 'USER'@'HOST' to database 'DBNAME'" when using LOCK TABLES

In case you cannot give the privilege to the user, then use the parameter --single-transaction to mitigate the problem. The command changes as follows.

USER="myUser"; PASS="myPASS"; HOST="myHost"; mysqldump -u "$USER" -p"$PASS" -h "$HOST" --single-transaction --all-databases > "`date +%F`-backup-all.$HOST.sql"