===== Commands that usually I forget =====


==== Restart DNS (Flush DNS Cache in Suse) ====

  service nscd restart

==== Users management for HTTP access (Suse) ====

Suse version, but I guess it's similar for other distributions. \\
In the example below, the file that contains the users (including encrypted passwords and information such as name, email, etc..)  in //htpasswd.users//. \\
If //username// does not exist it's created, otherwise it's updated. \\
The command requests the password for //username//.

Nagios related example:
  htpasswd2 /usr/local/nagios/etc/htpasswd.users username


==== Change Owner ====

Use the **chown** command to change owner to one or many files.
The example below change the owner of folder ''my_folder'' to //wwwrun// user and //www// group. \\
The **//-R//** parameter (recurring) analyzes //all// subfolders and files changing the owner and group as above. 

  chown -R wwwrun:www /srv/www/htdocs/my_folder


==== Search for installed Package ====

=== RedHat, Fedora Core, Suse Linux, CentoOs distribution ===
Use **rpm** command as follows to list all installed packages
  rpm -qa
  rpm -qa | grep 'package-name'
  rpm -qa | grep -i '*httpd*'

=== Debian or Ubuntu Linux distribution ===
You can use **dpkg** command to list all installed packages:
  dpkg --list
  dpkg --list | grep 'package-name'
  dpkg --list | grep -i '*php*'


==== Redirect standard output to a PC ====

If a command has a graphical output (like //yast2//) and the server has no display (or you are remotly connected via terminal emulator), it's possible to redirect the output to a different PC using the command **export**. \\
The PC must run a listener, such as Xmanager. Command example:

  Format:    export DISPLAY=ip_address:0.0
  
  Example:   export DISPLAY=172.28.9.231:0.0

==== Set Proxy authetication ====

To manually set the proxy with authentication, use the format:

  Acquire::http::proxy "http://user:password@proxy_server:port/";

For example, to set the proxy for //apt-get// in Ubuntu, change the configuration file ///etc/apt/apt.conf//:
<code>
Acquire::http::proxy "http://user:password@my_proxy:8080/";
Acquire::ftp::proxy "ftp://user:password@my_proxy:8080/";
Acquire::https::proxy "https://user:password@my_proxy:8080/";
</code>


==== Set SMTP server (SUSE)====

In file ///etc/postfix/main.cf// add/update the key:

  relayhost = my_SMTP_server.my_domain
  

==== Up Ethernet Interface (SUSE)====

First get the interface name with the command **ifconfig**:

<code>
ifconfig
eth0      Link encap:Ethernet  HWaddr 00:50:56:B1:00:2A
          inet addr:172.28.9.87  Bcast:172.28.15.255  Mask:255.255.248.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:9756009 errors:0 dropped:0 overruns:0 frame:0
          TX packets:53735102 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:902184895 (860.3 Mb)  TX bytes:79080496538 (75417.0 Mb)

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:16662619 errors:0 dropped:0 overruns:0 frame:0
          TX packets:16662619 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:8355092362 (7968.0 Mb)  TX bytes:8355092362 (7968.0 Mb)
</code>

Then use the **ifup** command:  
  ifup eth0