The RewriteLog directive sets the name of the file to which the server logs any rewriting actions it performs. If the name does not begin with a slash ('/') then it is assumed to be relative to the Server Root. The directive should occur only once per server config.
Note: To disable the logging of rewriting actions it is not recommended to set file-path to /dev/null, because although the rewriting engine does not then output ...

Example how to move files with RSYNC

This articles is valid for all Unix flavours that have rsync available.

Rsync is one powerful tool for Linux administrators that allows one to synchronise two directories/paths based on source/destination model.

Among the many features it offers, there is one particularly useful when a migration (not backup) has to be performed and the source directory has to be wiped.

The rsync option that allows for source files and ...

Newly created users in Debian and Centos Linux will have the default shell "sh" as seen below:


Only root user or a sudo enabled non-root user will be able to change shells. The Linux command to change a user's login shell is "chsh".

All information about a process is kept in the kernel/process table. To query this information, the pseudo filesystem /proc or the PS command can be used (there also other tools, but I will focus on "ps" here).

The PS command can show both the start time and date of a process and the elapsed time since the process has started. The interesting PS options and modifiers are found in the manual:

Reloading profile, Reloading profile under Unix, Reloading profile under Linux,Reloading profile under BSD, how to reload Unix profile.

Use the following command to reload a unix profile (/etc/profile, ~/.profile, ~/.bash_profile ...):


Notice: . (dot) is a command that originates from source command. On some unix flavours (FreeBSD 6 for example) source command works still:


.profile settings overwrite those in /etc/profile. You can also ...

Everytime when configuring SSL vhost in apache/nginx or any other webserver, security is the main concern. This means that you have to be careful which cipher blocks you want the webserver to impose.

To check a specific ssl cipher suite used in Apache/Nginx:


Now, to see actual ciphers contained by this cipher suite:

# openssl ciphers -v 'SSLCipherSuite !aNULL:!eNULL:!EXPORT:!DSS:!DES:!SSLv2:RC4-SHA:RC4-MD5:ALL'
RC4-SHA SSLv3 Kx=RSA Au=RSA Enc=RC4(128) Mac=SHA1 ...

To list openssl supported ciphers and see each cipher's characteristics the "ciphers" module in openssl can be used with verbose:


# openssl ciphers -v
DHE-RSA-AES256-SHA SSLv3 Kx=DH Au=RSA Enc=AES(256) Mac=SHA1
DHE-DSS-AES256-SHA SSLv3 Kx=DH Au=DSS Enc=AES(256) Mac=SHA1
AES256-SHA SSLv3 Kx=RSA Au=RSA Enc=AES(256) Mac=SHA1
EDH-RSA-DES-CBC3-SHA SSLv3 Kx=DH Au=RSA Enc=3DES(168) Mac=SHA1
EDH-DSS-DES-CBC3-SHA SSLv3 Kx=DH Au=DSS Enc=3DES(168) Mac=SHA1
DES-CBC3-SHA SSLv3 Kx=RSA Au=RSA Enc=3DES(168) Mac=SHA1
DES-CBC3-MD5 SSLv2 Kx=RSA Au=RSA Enc=3DES(168) Mac=MD5
DHE-RSA-AES128-SHA SSLv3 Kx=DH Au=RSA Enc=AES(128) Mac=SHA1
DHE-DSS-AES128-SHA SSLv3 ...

Giving that a system has ntpd up&running, ntpq utility can be used to check system time synchronization:


Man ntpq quote:

In Bash shell, redirecting output to a existing file is not possible if the "noclobber" bash option is set.

To overcome this, use the ">|" or ">>" redirect operator. The pipe will overwrite the file if you are using single angle bracket and append if you're using double angle brackets.

How to forcely overwrite a file with output from a command:

# cat output
# echo 'output' >output
-bash: output: cannot overwrite existing file ...

A little background from bashref:http://www.gnu.org/software/bash/manual/bashref.html