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As I’ve been written on my previous post about Maildir Replication using ChironFS in postfix, I will explain step by step it can also be done by using drbd and ocfs2.
note: if your Linux distribution is shipped with a kernel older than 2.6.33 you have to install a kernel module package and packages for the user land code. If your distribution contains a Linux-2.6.33 kernel or newer you only need to install the user land code.
In my case i have my linux distribution older than 2.6.33, so i will also compile drbd kernel module.
Download drbd source and create Binary RPMS packages
$ wget http://oss.linbit.com/drbd/8.3/drbd-8.3.10.tar.gz $ tar xvzf drbd-8.3.10.tar.gz $ cd drbd-8.3.10 $ ./configure --enable-spec --with-km $ cp ../drbd*.tar.gz `rpm -E %_sourcedir` $ rpmbuild -bb drbd.spec $ rpmbuild -bb drbd-km.spec $ sudo rpm -ivh /path/to/RPMS/drbd-*
I’ll be using loop files for this setup since I don’t have access to raw partitions.
but if you have raw block device available you can subtitute this part:
resource r0 { meta-disk internal; device /dev/drbd0; disk /dev/loop0;
Into:
resource r0 {
meta-disk internal;
device /dev/drbd0;
disk /dev/sdxx;
sdxx can be sda1, sdb1 sdb2 or what ever your raw disk device called
# dd if=/dev/zero of=/drbd-postfix.img bs=1M count=5000 # losetup /dev/loop0 /drbd-postfix.img
Place this DRBD resource file in /etc/drbd.d/r0.res. Be sure to adjust the server names and IP addresses for your servers.
resource r0 {
meta-disk internal;
device /dev/drbd0;
disk /dev/loop0;
syncer { rate 1000M; }
net {
allow-two-primaries;
after-sb-0pri discard-zero-changes;
after-sb-1pri discard-secondary;
after-sb-2pri disconnect;
}
startup { become-primary-on both; }
on postfix1 { address 192.168.200.18:7789; }
on postfix2 { address 192.168.200.114:7789; }
}
A web badge is a small image or text used on websites to promote web standards, products used in the creation of a web page or product, to indicate a specific content license that is applied to the content or design of a website, to comply with an application’s terms of service, to encourage your visitors to check your social network status, or even to display visitor’s informations. such as ip address, user agent, hostname etc.
Today’s story, we’ll make a badge for visitor’s ip address using php and javascript. This badge, for an example:
[cfields]v_ip_badge[/cfields]
create a php script called ipaddr.php as follows
<?php
if ( isset($_SERVER["REMOTE_ADDR"]) ) {
$ip=$_SERVER["REMOTE_ADDR"] . ' ';
} else if ( isset($_SERVER["HTTP_X_FORWARDED_FOR"]) ) {
$ip=$_SERVER["HTTP_X_FORWARDED_FOR"] . ' ';
} else if ( isset($_SERVER["HTTP_CLIENT_IP"]) ) {
$ip=$_SERVER["HTTP_CLIENT_IP"] . ' ';
}
$IpAddr = $ip;
?>
if (typeof(v_ip_BackColor)=="undefined")
v_ip_BackColor = "white";
if (typeof(v_ip_ForeColor)=="undefined")
v_ip_ForeColor= "black";
if (typeof(v_ip_FontPix)=="undefined")
v_ip_FontPix = "16";
if (typeof(v_ip_DisplayFormat)=="undefined")
v_ip_DisplayFormat = "You are visiting from:<br>IP Address: %%IP%%";
if (typeof(v_ip_DisplayOnPage)=="undefined" || v_ip_DisplayOnPage.toString().toLowerCase()!="no")
v_ip_DisplayOnPage = "yes";
v_ip_HostIP = "<?php echo $IpAddr ?>";
if (v_ip_DisplayOnPage=="yes") {
v_ip_DisplayFormat = v_ip_DisplayFormat.replace(/%%IP%%/g, v_ip_HostIP);
document.write("<table border='0' cellspacing='0' cellpadding='5' style='background-color:" + v_ip_BackColor + "; color:" + v_ip_ForeColor + "; font-size:" + v_ip_FontPix + "px'><tr><td>" + v_ip_DisplayFormat + "</td></tr></table>");
}
In this tutorial I will describe how to set up postfix and maildir which can automatically replicate email when email is delivered. We will not touch the postfix configuration at all. we will manipulate maildir directory behavior using ChironFS, instead.
This the Chiron Filesystem. It is a Fuse based filesystem. It’s main purpose is to guarantee filesystem availability using replication. But it isn’t a RAID implementation. RAID replicates DEVICES not FILESYSTEMS.
RPM:
$ rpmbuild --rebuild chironfs-1.0.0-1.fc8.src.rpm $ rpm -ivh /path/to/chironfs-1.0.0-1.fc12.rpm
When I was looking for ways to replicate the contents of memcached for high-availability performance, I found this memcached-repcached application. that has the ability to replicate the contents of one memcached to another.
People probably already know about memcached . It’s a robust, high performance key-value based memory object cache interface. but unfortunately, lack the ability to create redundancy and replication in memcached server clusters. although replication could be done at the application level. However, it all depends on each individual’s taste.
This is a quick and dirty experiment I have tried using memcached-repcached application on 2 servers.
Download memcached-repcached from repcached.lab.klab.org
Or you can download source rpm version from here
[download#33]
On the first server and second server extract memcached-1.2.8-repcached-2.2.tar.gz, compile with –enable-replication option when configure.
$ tar xvzf memcached-1.2.8-repcached-2.2.tar.gz $ cd memcached-1.2.8-repcached-2.2 $ ./configure --enable-replication $ make
I have found a very cool program for monitoring and debugging Memcached server, it’s called phpMemcachedAdmin. This program allows to see in real-time (top-like) or from the start of the server, stats for get, set, delete, increment, decrement, evictions, reclaimed, cas command, as well as server stats (network, items, server version) with googlecharts and server internal configuration You can go further to see each server slabs, occupation, memory wasted and items (key & value).
Another part can execute commands to any memcached server : get, set, delete, flush_all, as well as execute any commands (like stats) with telnet To extract these informations, phpMemCacheAdmin uses, as you wish, direct communication with server, PECL Memcache or PECL Memcached API.
Explanation above is an excerpt from the website. This is a simple guide how do I install phpMemCachedAdmin.
# wget http://phpmemcacheadmin.googlecode.com/files/phpMemcachedAdmin-1.2.1-r233.tar.gz
Since we will install in /var/www/html/memcached/ directory, run this command:
# mkdir -p /var/www/html/memcached # tar -xvzf phpMemcachedAdmin-1.2.1-r233.tar.gz -C /var/www/html/memcached/ # chmod 0777 /var/www/html/memcached/Config/Memcache.php
( i’m using apache as reverse proxy backend )
# cd /etc/httpd/conf.d # vi memcached.conf
If you have multiple load balanced webservers all serving the same site, sessions should be shared among those
servers, and not reside on each server individually. Because we don’t know where user gets load-balanced to which backend server. A common way solving this problems are by using custom class that overrides default behavior and stores sessions in a MySQL database. All webservers in clusters connect to the same database. However, the main problem that must be taken into consideration when using a database is the bottleneck.
http {
upstream backend {
server 192.168.1.1:8000 weight=3;
server 192.168.1.2:8001;
server 192.168.1.3:8002;
server 192.168.1.4:8003;
}
server {
listen 80;
server_name www.example.com;
location / {
proxy_pass http://backend;
}
}
}
Normally, to check if my server smtp connection alive, I just do telnet to port 25 from my workstation. if the smtp banner displayed, it means that the connection to the smtp server is good. I have done this for years. 😆
$ telnet smtp.example.com 25 Trying xxx.xxx.xx.xxx... Connected to xxx.xxx.xx.x. Escape character is '^]'. 220 smtp.example.com ESMTP Postfix ehlo host.example.com 250-smtp.example.com 250-PIPELINING 250-SIZE 52428800 250-ETRN 250-STARTTLS 250-AUTH LOGIN PLAIN 250-AUTH=LOGIN PLAIN 250-ENHANCEDSTATUSCODES 250-8BITMIME 250 DSN quit 221 2.0.0 Bye Connection closed by foreign host.
Although many tools that are deliberately created for this purpose, still, I prefer just using telnet to port 25. I have made a simple perl script, with the intention that the things I do for years manually can be done automatically.
I already have a list of users in a mysql database that I use for postfix smtp authentication/sasl.
I wonder, whether the list can be used for http authentication 😀 . Well, let’s find out.
First of all, of course we must compile nginx to support http_auth_pam_module module.
download ngx_http_auth_pam_module-1.2.tar.gz
When compiling from source build as usual adding the -add-module option:
./configure --add-module=$PATH_TO_MODULE
My pam_mysql for postfix smtp authentication /etc/pam.d/smtp
auth required pam_mysql.so user=user passwd=pass host=localhost db=db table=mailbox usercolumn=username passwdcolumn=password crypt=1 md5=1 sqlLog=0 account sufficient pam_mysql.so user=user passwd=pass host=localhost db=db table=mailbox usercolumn=username passwdcolumn=password crypt=1 md5=1 sqllog=0