How to resize or scale a list of images on linux

Here is a simple but powerful command when you got several images that you want to shrink:


mogrify -scale 50% *.jpg


This will reduce all the images by 50%


Or if you just want to reduce one image to 200x200 pixels for example:



convert -scale 200x200 image.jpg image_small.jpg


Installing virtualbox on Ubuntu 9.04


# virtualbox
WARNING: The character device /dev/vboxdrv does not exist.
Please install the virtualbox-ose-source package and the appropriate
headers, most likely linux-headers-generic.

You will not be able to start VMs until this problem is fixed.



root@ubuntu-laptop:/home/camafla# apt-get install linux-headers-server
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following extra packages will be installed:
linux-headers-2.6.28-11-server
The following NEW packages will be installed:
linux-headers-2.6.28-11-server linux-headers-server
0 upgraded, 2 newly installed, 0 to remove and 0 not upgraded.
Need to get 672kB of archives.
After this operation, 8139kB of additional disk space will be used.
Do you want to continue [Y/n]? y
Get:1 http://archive.ubuntu.com jaunty/main linux-headers-2.6.28-11-server 2.6.28-11.42 [669kB]
Get:2 http://archive.ubuntu.com jaunty/main linux-headers-server 2.6.28.11.15 [3388B]
Fetched 672kB in 6s (104kB/s)
Selecting previously deselected package linux-headers-2.6.28-11-server.
(Reading database ... 157949 files and directories currently installed.)
Unpacking linux-headers-2.6.28-11-server (from .../linux-headers-2.6.28-11-server_2.6.28-11.42_i386.deb) ...
Selecting previously deselected package linux-headers-server.
Unpacking linux-headers-server (from .../linux-headers-server_2.6.28.11.15_i386.deb) ...
Setting up linux-headers-2.6.28-11-server (2.6.28-11.42) ...
Examining /etc/kernel/header_postinst.d.
run-parts: executing /etc/kernel/header_postinst.d/dkms
* Running DKMS auto installation service for kernel 2.6.28-11-server
* vboxdrv (2.1.4)... vboxdrv (2.1.4): Installing module.
.............
......
[ OK ]
* vboxnetflt (2.1.4)... vboxnetflt (2.1.4): Installing module.
............
......
[ OK ]
run-parts: executing /etc/kernel/header_postinst.d/nvidia-common

Setting up linux-headers-server (2.6.28.11.15) ...



LPI 102 exam reference card (or cheat sheet if you like)

I recently cleared the LPIC-1 certification (LPI certification Level 1) , as an educational exercise to study for my second exam (exam 102) I created a reference card that helped me remember some commands and key concepts for the exam.

I want to share this to anyone interested in taking this exam or just anyone who wants a quick linux reference card to the objectives included in the exam.

Download

PNG version: lpi-102-reference-card-v1.png

PDF version: lpi-102-reference-card-v1.pdf

Installing Oracle OCI8 and PHP

I will describe here the steps I needed to install oracle connectivity for php. It's supposed you have php installed, in my case
I had php 5.1.6 throught RPM:

# rpm -qa | grep php
php-5.1.6-20.el5_2.1
php-adodb-4.81-1.el5.rf
php-pecl-mailparse-2.1.1-1.el5.rf
phpmyadmin-2.11.8.1-1.el5.rf
php-odbc-5.1.6-20.el5_2.1
php-pecl-fileinfo-1.0.4-1.el5.rf
php-cli-5.1.6-20.el5_2.1
php-pear-file-1.2.2-1.el5.rf
php-eaccelerator-5.1.6_0.9.5.2-4.el5.rf
php-pecl-memcache-2.1.2-1.el5.rf
php-pear-db-1.7.13-2.el5.rf
php-common-5.1.6-20.el5_2.1


Distro:

# cat /etc/redhat-release
Red Hat Enterprise Linux Server release 5 (Tikanga)

1. Download and install the Instant Client rpms from oracle which you can get here http://www.oracle.com/technology/tech/oci/instantclient/instantclient.html.

This are the two files needed in my case:

# rpm -ivh oracle-instantclient11.1-basic-11.1.0.7.0-1.x86_64.rpm

# rpm -ivh oracle-instantclient11.1-devel-11.1.0.7.0-1.x86_64.rpm


2. Compile and install the oci8 extension:

Make sure you have the proper packages to compile a script like: php-devel, gcc,etc.


# pear install pecl/oci8

I used pear install pecl/oci8 instead of pear install oci8 because for some reason the second one returns an out of memory error and ignores the memory limit variable (memory_limit = XX ) from the
php.ini file.


When asked about this:

Please provide the path to the ORACLE_HOME directory. Use 'instantclient,/path/to/instant/client/lib' if you're compiling with Oracle Instant Client : autodetect

If you have oracle installed in the same server just hit enter. If not (you just want to connect to another server) type:

instantclient and enter or the path to the oracle libraries e.g: /usr/lib/oracle/11.1/client64/lib/.


3. Finally, edit your php.ini file (/etc/php.ini) and add the extension=oci8.so in the Dynamic extensions section. Don't forget to restart apache so the changes take effect in apache.


Additional information can be found here: http://www.oracle.com/technology/pub/notes/technote_php_instant.html.