:::: MENU ::::


  • Nov 21 / 2016
  • 0

Apache – mod_auth compatibility for 2.2 and 2.4

Since Apache 2.4, mod_auth changed and some directive like

Order allow,deny
Allow from all

that have been replaced with

Require all granted

If you want to automatically handle same configuration for multiple servers where different versions of Apache are installed, you can use this trick:

<IfModule mod_version.c>
  <IfVersion < 2.4>
    Order allow,deny
    Allow from all
  <IfVersion >= 2.4>
    Require all granted
<IfModule !mod_version.c>
  Order allow,deny
  Allow from all

Thanks to that change, your configuration will be working whatever version of Apache you’re using.

  • Nov 07 / 2016
  • 0

PostgreSQL – Check value is in array

With PostgreSQL, if you have a field containing an Array and you want to get all the results containing this value in the array, you can use the following command.

Here, we are looking for all the results in the table my_table containing my_value in the field my_array.

SELECT * FROM my_table WHERE 'my_value'=ANY(my_array) ORDER BY id;

   id  |        type        |             title             |             my_array                                                            
 93646 | this_is_my_type    | this_is_my_title              | {my_1,my_2,my_3,my_value,my_4,my_5}
 94184 | this_is_my_type    | this_is_my_title2             | {my_3,my_value,my_4,my_5}
 98240 | this_is_my_type    | this_is_my_title3             | {my_1,my_2,my_3,my_value}             

  • Oct 28 / 2016
  • 0

Add a confirmation dialog with bash

If you have a bash script doing some critical actions, it can be useful to add a confirmation dialog to double check with the user that he really wants to perform the action.

Here is a very simple script allowing this kind of checking:

echo "Welcome to your favourite script!"
read -r -p "Are you sure you want to execute it? [y/N] " response
if [[ $response =~ ^([yY][eE][sS]|[yY])$ ]]
  echo "Execution in progress..."
  # Write your action here
  echo "Action canceled."
echo "End of script."

Output will look like:

  • Case ‘yes’:
    $ bash script_yesno.sh 
    Welcome to your favourite script!
    Are you sure you want to execute it? [y/N] y
    Execution in progress...
    End of script.
  • Case ‘no’:
    $ bash script_yesno.sh 
    Welcome to your favourite script!
    Are you sure you want to execute it? [y/N] N
    Action canceled.

It’s up to you customizing it depending on your needs and your feelings!

  • Oct 19 / 2016
  • 0

Apache Tomcat – Get logs directly cleaned with rotation

Tomcat allows you to rotate easily your log files with AccessLogValve but it can be more difficult to get cleaning in logs directories automatically.

For that, you can easily use some smart find commands combined with actions:

  1. Get logs older than 3 days compressed so they can be smaller but still accessible
    find /var/log/tomcat/ -mtime +3 -regex ".*\.\(log\|txt\)$" -exec gzip "{}" \;
  2. Get logs older than 60 days deleted permanently
    find /var/log/tomcat/ -mtime +60 -name "*.gz" -exec rm "{}" \;

You will probably have to adjust the logs path depending on your needs, and you can also modify the retention time for each action.
Once the command looks correct with what you’re expecting, you can set them up as cron so it can be executed automatically every day.

  • Oct 14 / 2016
  • 0

Generate a random file with specific size

It’s possible to easily generate a random file with specific size filled differently depending on the needs:

  • Fill a 200MB file with zeroes
    dd if=/dev/zero of=/tmp/file.out bs=1024KB count=200
  • Fill a 200MB file with random values (longer than zeroes – depending on processor)
    dd if=/dev/random of=/tmp/file2.out bs=1024KB count=200

  • Sep 27 / 2016
  • 0

Escape sequences for SSH (when you’re stuck)

You can get stuck with your ssh session when your network is changing or when there’s a network disruption. You will face a lock leading to the unability to stop your session, even by doing a CTRL-C.

That’s why there’s some escape sequences you can use in that case (especially the first one when you’re stuck):

  ~.  - terminate connection (and any multiplexed sessions)
  ~B  - send a BREAK to the remote system
  ~C  - open a command line
  ~R  - Request rekey (SSH protocol 2 only)
  ~^Z - suspend ssh
  ~#  - list forwarded connections
  ~&  - background ssh (when waiting for connections to terminate)
  ~?  - this message
  ~~  - send the escape character by typing it twice

Note that escapes are only recognized immediately after newline.

Question ? Contact