Linux Windows System Administrator Help

memcached is a high-performance memory object caching system intended to speed up dynamic web applications by alleviating database load.

memcached is meant to work in concert with something like the MySQL query cache, not replace it. The two implementations excel at vastly different things: memcached is an object cache, while MySQL provides a query cache.

memcached is extremely fast. It uses libevent, which provides a mechanism to execute a callback function when a specific event occurs on a file descriptor, to scale to any number of open connections. On a modern Linux system memcached utilizes epoll, is completely non-blocking for network I/O, ensures memory never gets fragmented, and uses its own slab allocator and hash table to achieve 0(1) virtual memory allocation.

How it install it on Linux server ?

• Install dependency software (Libevent)

#curl -O http://monkey.org/~provos/libevent-1.4.9-stable.tar.gz
#tar -xzvf libevent-1.4.9-stable.tar.gz
#cd libevent*
#./configure
#make
#make install

• Now let’s download the newest Memcached source

#curl -O http://www.danga.com/memcached/dist/memcached-1.3.0.tar.gz
#tar zxf memcached-1.3.0.tar.gz
#cd memcached-1.3.0
#./configure
#make
#make install

• Then add /usr/local/lib to LD_LIBRARY_PATH in your .bash_profile

LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/usr/local/lib
export LD_LIBRARY_PATH

How it Works

First, you start up the memcached daemon on as many spare machines as you have. The daemon has no configuration file, just a few command line options, only 3 or 4 of which you’ll likely use:

Run Memcached as a daemon (d = daemon, m = memory, u = user, l = IP to listen to, p = port)

#memcached -d -m 1024 -u root -l 127.0.0.1 -p 11211 –u nobody

This starts memcached as a daemon (-d) on the IP address and port specified with -l and -p, respectively, running as the user nobody (-u), allocating 1024  for object storage (-m). You should adjust the amount of storage to suit your needs; many memcached installs run with 4 GB. Once you are comfortable with your startup options, add the appropriate command to your startup scripts.

Create a /etc/init.d/memcached file and add above line to start memcached when the server boots

With memcached installed and running, it’s time to get PHP talking to the object cache. While multiple PHP API exists, the one in the PECL repository is recommended. If you are running a newer version of PHP, installation is as simple as:

# pecl install memcache

Or you can use following steps to install PECL memcache manually.

#cd /usr/local/src
#curl -O http://pecl.php.net/get/memcache
#tar zxvf memcache*
#cd memcache-*
#phpize
#./configure
#make && make install

Now we have to make sure PHP loads the newly built memcache.so library by adding the following line to php.ini:

extension=memcache.so

Now restart Apache:

Service httpd restart

Once it sucussfully install you can create phpinfo() on your webserver should now confirm that memcache is installed.

Regards
AlexP

Svn(subversion) is used to maintain current and historical versions of files such as source code, web pages, and documentation. Its goal is to be a mostly-compatible successor to the widely used Concurrent Versions System (CVS).

It is very easy to install subversion client on linux OS using yum. You can us following command to install subversion client.

root@server [~]# yum install subversion

while installing subversion if you are getting following error  then it seem sot be perl-URI package is not installed on your server so you will have to install first before installing subversion client.

Please follow the following steps to install perl-URI package

You’ll login via SSH as root and run this command:

root@server [~]# yum install subversion

and then you may get this error:

Error: Missing Dependency: perl(URI) >= 1.17 is needed by package subversion

Here’s what you do next (copy/paste):

root@server [~]# wget  ftp://ftp.pbone.net/mirror/archive.fedoraproject.org/
fedora/linux/releases/7/Everything/i386/os/Fedora/
perl-URI-1.35-3.noarch.rpm 

root@server [~]# rpm -i perl-URI-1.35-3.noarch.rpm

root@server [~]# yum install subversion

Installed: subversion.x86_64 0:1.4.2-4.el5 subversion.i386 0:1.4.2-4.el5

Dependency Installed: neon.x86_64 0:0.25.5-10.el5 neon.i386 0:0.25.5-10.el5

Complete!

That’s it subversion client is successfully installed on your server you can check it using following command.

root@server [~]#svn --version
svn, version 1.1.4 (r13838)
compiled Aug 21 2005, 20:56:55

Copyright (C) 2000-2004 CollabNet.
Subversion is open source software, see http://subversion.tigris.org/
This product includes software developed by CollabNet (http://www.Collab.Net/).

The following repository access (RA) modules are available:

* ra_dav : Module for accessing a repository via WebDAV (DeltaV) protocol.
- handles 'http' schema
- handles 'https' schema
* ra_local : Module for accessing a repository on local disk.
- handles 'file' schema
* ra_svn : Module for accessing a repository using the svn network protocol.
- handles 'svn' schema

Regards

Alex P

IF you disable PHP function in php.ini file and if you want to enable any particular function only one account .Then You can however use suhosin to enable a function for one domain only.

How can you do that ?

After installing suhosin, remove all functions from disable_functions in php.ini and add in php.ini suhosin.executor.func.blacklist = “exec,passthru,shell_exec” and all the functions that you want to disable globally.

After that for each domain in the virtual host section you can add suhosin.executor.func.blacklist again but without the function that you need to enable. And so you will enable that function only for one domain.

Example:

<VirtualHost 127.0.0.1>
………..
………..
<IfModule mod_php4.c>
php_admin_value open_basedir “/usr/lib/php”
</IfModule>
<IfModule mod_php5.c>
php_admin_value open_basedir “/usr/lib/php”
php_admin_value suhosin.executor.func.blacklist = “passthru,shell_exec”
</IfModule>
…….
……
</VirtualHost>

In this example exec has been enabled for the VirtualHost. This way it will be better as you do not neet to modify all the virtual hosts only the ones that you need to enable one or more functions.

Regard’s

Alex P