Start or Stop Linux Service
Start a service:
sudo service apache2 startor
sudo /etc/init.d/apache2 start
Stop a service:
sudo service apache2 stopor
sudo /etc/init.d/apache2 stop
sftp and ssh with nautilus
1. Open nautilus
2. Press ctrl + l
3. type
sftp://username@myserver.com
or
ssh://username@myserver.com
4. Enter your password
5. enjoy!
Introduction to Apt
All of these commands must be run as root or with superuser privileges.
Installation
apt-get install package_name
or
apt-get install package_name1 package_name2 package_name3
apt-get build-dep package_nameThis command searches the repositories and installs the build dependencies for package_name.
Maintenance
apt-get updateRun this command periodically to make sure your source list is up-to-date or after changing sources list.
apt-get upgradeThis command upgrades all installed packages.
apt-get dist-upgradeThe same as the above, except add the “smart upgrade” checkbox. It tells APT to use “smart” conflict resolution system,
and it will attempt to upgrade the most important packages at the expense of less important ones if necessary.
apt-get checkIt does an update of the package lists and checks for broken dependencies.
apt-get -f install
Do this if you get complaints about packages with “unmet dependences”.
apt-get autocleanThis command removes .deb files for packages that are no longer installed on your system.
apt-get cleanThe same as above, except it removes all packages from the package cache. This may not be desirable if you have a
slow internet connection, since it will cause you to re-download any packages you need to install a program.
Removal
apt-get remove package_nameThis command removes an installed package, leaving configuration files intact.
apt-get purge package_nameThis command completely removes a package and the associated configuration files.
apt-get autoremoveThis command removes packages that were installed by other packages and are no longer needed.
Search
apt-cache search search_termThis command will find packages that include search_term.
apt-cache show package_nameThis command shows the description of package package_name.
and other relevant information including version, size, dependencies and conflicts.
dlocate package_name
This command determines which installed package owns package_name.
For more information please visit https://help.ubuntu.com/community/AptGet/Howto
Set PHP configuration options in Apache using directives
Apache directives to change the PHP configuration:
php_value name value
Sets the value of the specified directive.
php_flag name on|off
Sets a boolean configuration directive.
php_admin_value name value
Sets the value of the specified directive. This can not be used in .htaccess files.
php_admin_flag name on|off
Used to set a boolean configuration directive. This can not be used in .htaccess files.
Let’s see some examples:
<IfModule mod_php5.c> php_value include_path ".:/usr/local/lib/php" php_admin_flag engine on </IfModule>
<Directory /var/www/vhosts/mydomain.com/httpdocs> php_admin_value open_basedir "/var/www/vhosts/mydomain.com/httpdocs:/var/www/vhosts/mydomain.com/files" </Directory>
<Directory /var/www/vhosts/mydomain.com/httpdocs> php_value include_path ".:/usr/local/lib/php" php_flag display_errors Off php_value upload_max_filesize 2M </Directory>
Install development tools and kernel headers for Fedora
Development Tools Installation
yum groupinstall 'Development Tools'Kernel headers Installation
yum install kernel-devel kernel-headersor
yum install kernel-devel-$(uname -r) kernel-headers-$(uname -r)
CentOS SSH Server Installation
You need to install the following package:
su -yum -y install openssh-server
Start the service
chkconfig sshd on
service sshd start
Remote Desktop Support in CentOS
Remote Desktop Support
Become root
su -Installation
yum install vinoSetting up Remote Desktop Access
Goto System->Preferences->Remote Desktop
and enable these settings on the remote desktop window preferences:
1. Allow other users to view your desktop.
2. Allow other users to control your desktop.
3. Require the user to enter this password: your_password
4. Configure network automatically to accept connections.
How do I find out the MAC address of my Linux system?
I know that is something common but people keep questioning me about how to get the ethernet mac address on their linux system. So, here it is. Issue the following command:
ifconfig eth0 | grep HWaddr
QR code
QR Code (Quick Response Code) is two dimensional code which is categorized in matrix code. The code consists of black modules arranged in a square pattern on a white background. The information encoded can be made up of four standardized kinds of data (numeric, alphanumeric, byte/binary, Kanji). The QR Code was designed for high speed reading, high capacity, high density, error correcting, structured append and high speed decoding.
Standards
- October 1997 – AIM (Association for Automatic Identification and Mobility) International
- January 1999 – JIS X 0510
- June 2000 – ISO/IEC 18004:2000 Information technology – Automatic identification and data capture techniques – Bar code symbology – QR code
- 1 September 2006 – ISO/IEC 18004:2006 Information technology – Automatic identification and data capture techniques – QR Code 2005 bar code symbology specification
Storage
The amount of data that can be stored in the QR Code symbol depends on the datatype and error correction level. The maximum storage capacities are as follows:
| Numeric only | Max. 7,089 characters (0, 1, 2, 3, 4, 5, 6, 7, 8, 9) |
| Alphanumeric | Max. 4,296 characters (0–9, A–Z [upper-case only], space, $, %, *, +, -, ., /, :) |
| Binary/byte | Max. 2,953 characters (8-bit bytes) (23624 bits) |
| Kanji/Kana | Max. 1,817 characters |
Encryption
There are a few implementations. An Android app manages encryption and decryption of QR codes using DES algorithm. Japanese immigration use encrypted QR Codes when placing visas in passports.
Error Correction
| Level L | 7% of codewords can be restored. |
| Level M | 15% of codewords can be restored. |
| Level Q | 25% of codewords can be restored. |
| Level H | 30% of codewords can be restored. |
License
The use of QR Codes is free of any license. The QR Code is clearly defined and published as an ISO standard.
