email Validation script

#!/usr/bin/perl -w
use Net::SMTP;
#Create a new object with 'new'.
BEGIN {
use lib '/net/lib/perl';
require VVV::DNS;
require Net::SMTP;
}


@gl::myips = qw(
202.XX.XX.XX
202.XX.XX.XX
202.XX.XX.XX
202.XX.XX.XX
202.XX.XX.XX
);




my $res = DNS::dnshandle('202.XX.XX.XX');

# list of email iDs
my $file = $ARGV[0];
open (IN, "$file") || die "Require valid filename of emailids $!\n";
my @arrids = <IN>;
close IN;

chomp @arrids;

#function to check valid email

sub valid_email {
my($id1) = @_;
if ($id1 =~ /^[\w\-\_\.]+\@[\w\-\_\.]+$/) {
print "$id1 is valid";
return 1;
} else {
print "$id1 is invalid";
return 0;
}
}

#
# 0 ==>; email is valid
# 1 ==>; email invalid
# 2 ==>; email could not be verified try later
#


sub emailid_invalid {
my($id,$mxref,$smtpbind)=@_;
print "MX HOST for domain = ". $mxref->[0] ."\n";
$smtp = Net::SMTP->new(
Host => $mxref->[0],
Timeout => 30,
LocalAddr => $smtpbind,
Debug => 1,
Hello=>'company.com',
);
unless($smtp){
print "############Could not connect to ...#########\n";
return 2;
}

#Send the MAIL command to the server.
$smtp->mail("user1\@
company.com") || return(2);
print $smtp->to("$id");
my $errcode = $smtp->code();
if ( $errcode =~ /^25/ ) {
return 0;
print " this email ID is correct" ;
} elsif ($errcode =~ /^5/ ) {
return 1;
print " $errcode this email ID is incorrect" ;
} elsif ($errcode =~ /^4/ ) {
print " deffered connection ";
return 3;
}

$smtp->quit();
}



open(VALID,">", " /opt/valid");
open(INVALID,"/opt/invalid");
open(TRYAGAIN,"/opt/RETRY");

my @bindips;

foreach my $id (@arrids ) {
print "Checking ID: $id\n";
next unless (valid_email($id));
print "\nVALID Continue........\n";

my ($uname,$fulldomain) = split(/\@/, $id);
my @mxrec1 = DNS::mxrec($res,$fulldomain);

unless(scalar(@mxrec1)){
print INVALID "$id\n";
next;
}
unless(scalar @bindips){
push @bindips,@gl::myips;
}
my $smtpbind = shift(@bindips);

print STDERR "BIND as $smtpbind\n";

sleep 1;
my $ret = emailid_invalid($id,\@mxrec1,$smtpbind);
if($ret == 0){
print VALID "$id\n";
} elsif ($ret == 1) {
print INVALID "$id\n";
} elsif($ret == 2) {
print TRYAGAIN "$id\n";
} elsif($ret == 3) {
print TRYAGAIN "$id\n";
}

}


Documentation on server backup

Now On the backupserver machines


mkdir /net/serverbackup ----------> location where all the tar.gz files are stored


This scritpt will wget the flles from vairous server


vi /usr/local/bin/serverbackup



#!/bin/bash
set -x
DIR=/net/serverbackup
SERVERINFO=/net/serverbackup/serverbackupfiles
cd /net/serverbackup

if [ -d $DIR ] ;then
if [ -f $SERVERINFO ];then

for i in `cat $SERVERINFO |awk -F "|" '{print $2}'`
do
`cat $SERVERINFO |grep $i |awk -F "|" '{print $3}'``date +%Y%m%d`.tgz;
done
else
echo " serverbackupfiles does not exist "
fi
else
echo " serverbackup dir does not exist "
fi



This file (serverbackupfiles) is requied by the "serverbackup" script
cat /net/serverbackup/serverbackupfiles
|server112|wget --user=agnello --password=username http:///server112.com/serverbackup/pamserver2.



crontab -e

##for serverbackup to weget the files
0 11 * * * /usr/local/bin/serverbackup

Now On the system to be backed up

cd /net/serverbackup

ln -s /net/serverbackup /var/www/html/serverbackup


vi /usr/local/bin/serverbackupdaily
#!/bin/bash
#
set -x
backupfile1="`date '+%Y%m%d'`"
backupfile="servername.$backupfile1.tgz"
if cd /; then
tar zcf /tmp/$backupfile --exclude-from=/etc/backup/excludedaily `cat /etc/backup/BACKUPDAILY`
mv /tmp/$backupfile /net/serverbackup
chown -R web.web /net/serverbackup
fi

exit 0


vi /etc/httpd/conf/httpd.conf
#setting for serverbackup


AllowOverride AuthConfig
AuthName "serverBackup login"
AuthType Basic
AuthUserFile /net/serverbackup/.htpasswd
AuthGroupFile /dev/null
require user serverbackup
Order deny,allow
Deny from all
Allow from all


htpasswd -bc /net/serverbackup/.htpasswd serverbackup password

crontab -e
##for serverbackup
0 06 * * * /usr/local/bin/serverbackupdaily

Script to do mysqcheck

#!/usr/bin/perl
# this script can be run by command line to check each table on every database on every databases

my $a = `hostname`;
my @dbs =`mysql -u root -p[password] -e "show databases" | grep -v "Database" `;


foreach $i(@dbs){
chomp($i);
my @aa = `mysql -u root -p[password] $i -e 'show tables' |grep -v 'Tables_in_'`;
next if ($i =~/Tables_in_$i/);
foreach $r(@aa) {
chomp($r) ;
$d = `mysqlcheck -u root -p[password] $i $r` ;
print "checking table = $r of database $i \n";
if ($d =~/error/ ) {
print " the table $i is corrupted \n";
system(`/usr/local/bin/smtpmail -t a\@alertme.com -f admin\@serverone.com -h 192.168.2.105 -s "th table is courupted" -b "the table is $r of database $i on server $a is courrupted ..kindly check" `) ;

}
}
}

iptables examples

# firewall.stop
# Script to flush all firewall rulesets
#

set -x

#!/bin/sh
# My system IP/set ip address of server
# Flushing all rules
iptables -F
iptables -X

# Setting default filter policy
iptables -P INPUT DROP
iptables -P OUTPUT DROP
iptables -P FORWARD DROP


# Allow unlimited traffic on loopback
iptables -A INPUT -i lo -j ACCEPT
iptables -A OUTPUT -o lo -j ACCEPT





# Allow incoming ssh only
iptables -A INPUT -p tcp -s 54.263.22.76 -d 306.143.211.234/gc --sport 513:65535 --dport 22 -m state --state NEW,ESTABLISHED -j ACCEPT

iptables -A INPUT -p tcp -s 203.122.55.101 -d 306.143.211.234/gc --sport 513:65535 --dport 22 -m state --state NEW,ESTABLISHED -j ACCEPT

iptables -A OUTPUT -p tcp -s 208.183.110.234 -d 0/0 --sport 22 --dport 513:65535 -m state --state ESTABLISHED -j ACCEPT

#allow mysql connection
iptables -A INPUT -p tcp -s 54.263.22.76 --sport 1024:65535 -d 208.183.110.234 --dport 3306 -m state --stateNEW,ESTABLISHED -j ACCEPT

iptables -A INPUT -p tcp -s 208.183.110.234 --sport 1024:65535 -d 306.143.211.234/gc --dport 3306 -m state --state NEW,ESTABLISHED -j ACCEPT

iptables -A OUTPUT -p tcp -s 208.183.110.234 --sport 3306 -d 0/0 --dport 1024:65535 -m state --state ESTABLISHED -j ACCEPT




#allow FTP connection
iptables -A INPUT -p tcp -s 54.263.22.76 --sport 1024:65535 -d 306.143.211.234/gc --dport 21 -m state --state NEW,ESTABLISHED -j ACCEPT

iptables -A INPUT -p tcp -s 208.183.110.234 --sport 1024:65535 -d 306.143.211.234/gc --dport 21 -m state --stateNEW,ESTABLISHED -j ACCEPT

iptables -A OUTPUT -p tcp -s 208.183.110.234 --sport 21 -d 0/0 --dport 1024:65535 -m state --state ESTABLISHED-j ACCEPT


#open smtp port 25
iptables -A INPUT -p tcp -s 0/0 --sport 1024:65535 -d 306.143.211.234 --dport 25 -m state --state NEW,ESTABLISHED -j ACCEPT

iptables -A OUTPUT -p tcp -s 306.143.211.234 --sport 25 -d 0/0 --dport 1024:65535 -m state --state ESTABLISHED-j ACCEPT


#open port 465
iptables -A INPUT -p tcp -s 0/0 --sport 1024:65535 -d 306.143.211.234 --dport 465 -m state --state NEW,ESTABLISHED -j ACCEPT

iptables -A OUTPUT -p tcp -s 306.143.211.234 --sport 465 -d 0/0 --dport 1024:65535 -m state --state ESTABLISHED -j ACCEPT


#open http port
# allow incoming connectino http
iptables -A INPUT -p tcp -s 0/0 --sport 1024:65535 -d 06.183.111.235 --dport 80 -m state --state NEW,ESTABLISHED -j ACCEPT

iptables -A OUTPUT -p tcp -s 306.143.211.234 --sport 80 -d 0/0 --dport 1024:65535 -m state --state ESTABLISHED-j ACCEPT


# allow outgoing connectino http
iptables -A OUTPUT -p tcp -s 306.143.211.234 --sport 1024:65535 -d 0/0 --dport 80 -m state --state NEW,ESTABLISHED -j ACCEPT
iptables -A INPUT -p tcp -s 0/0 --sport 80 -d 306.143.211.234 --dport 1024:65535 -m state --state ESTABLISHED -j ACCEPT






#open dns port

#iptables -A OUTPUT -p tcp -s 306.143.211.234 --sport 53 -d 0/0 --dport 1024:65535 -m state --state ESTABLISHED -j ACCEPT

#iptables -A INPUT -p tcp -s 0/0 --sport 1024:65535 -d 306.143.211.234 --dport 53 -m state --state NEW,ESTABLISHED -j ACCEPT



#iptables -A OUTPUT -p udp -s 306.143.211.234 --sport 53 -d 0/0 --dport 1024:65535 -m state --state ESTABLISHED -j ACCEPT

#iptables -A INPUT -p udp -s 0/0 --sport 1024:65535 -d 306.143.211.234/gc --dport 53 -m state --state NEW,ESTABLISHED -j ACCEPT



##allow icmp ports
iptables -A INPUT -p tcp -m tcp --sport 53 --dport 1024:65535 -m state --state ESTABLISHED -j ACCEPT
iptables -A INPUT -p udp -m udp --sport 53 --dport 1024:65535 -m state --state ESTABLISHED -j ACCEPT
iptables -A OUTPUT -p tcp -m tcp --sport 1024:65535 --dport 53 -m state --state NEW,ESTABLISHED -j ACCEPT
iptables -A OUTPUT -p udp -m udp --sport 1024:65535 --dport 53 -m state --state NEW,ESTABLISHED -j ACCEPT





####
iptables -A INPUT -p icmp --icmp-type echo-reply -j ACCEPT
iptables -A OUTPUT -p icmp --icmp-type echo-request -j ACCEPT



# make sure nothing comes or goes out of this box
iptables -A INPUT -j DROP
iptables -A OUTPUT -j ACCEPT

Mounting a new HDD on Linux

There are many reasons why you would need to add a new drive to your Linux box. You might have out-grown your current space limitations, or you may want to add a separate drive for a specific project or service. In any case, if you follow this guide, you should have no problems. First, you must be familiar with the naming scheme Linux uses for your drives. For purposes if this article, everything highlighted in blue is the command you must type at the terminal prompt. Anything hightlighted in red indicates changes made by a previous command or something you should pay special attention to. Anything highlighted in green is simply the standard output from a terminal or issued command. The machine used for this guide is running Red Hat Entperise Linux.





Conventional Naming
This article assumes you know the difference between primary, extended and logical partitions. In the following example, I added a SCSI hard drive with one primary partition. With that being said, I'll continue explaining the naming scheme. Linux gives each drive a 3 letter name followed by a partition number. If you are using IDE drives, these will all be named hd**. Where hd denotes the drive and the next two variables are aassociated with IDE order (primary master, primary slave, etc) and partition number. So, your primary master drive will always be named hda. If you are using SCSI drives, everything remains the same except instead of using hd, drives are named sd**. Your SCSI primary master drive will always be named sda. All of these devices reside under the /dev portion of your Linux file system. For instance, as root, you can issue the following command to view the naming combinations possible for your system. Remember, in this example, I am using SCSI hardware. If you are using IDE, simply use hd is place of sd here.


[root@roswell root]# ls /dev/sda*
/dev/sda /dev/sdab10 /dev/sdad12 /dev/sdaf14 /dev/sdah2 /dev/sdaj4 /dev/sdal6
/dev/sda1 /dev/sdab11 /dev/sdad13 /dev/sdaf15 /dev/sdah3 /dev/sdaj5 /dev/sdal7
/dev/sda10 /dev/sdab12 /dev/sdad14 /dev/sdaf2 /dev/sdah4 /dev/sdaj6 /dev/sdal8
/dev/sda11 /dev/sdab13 /dev/sdad15 /dev/sdaf3 /dev/sdah5 /dev/sdaj7 /dev/sdal9
/dev/sda12 /dev/sdab14 /dev/sdad2 /dev/sdaf4 /dev/sdah6 /dev/sdaj8 /dev/sdam
/dev/sda13 /dev/sdab15 /dev/sdad3 /dev/sdaf5 /dev/sdah7 /dev/sdaj9 /dev/sdam1
/dev/sda14 /dev/sdab2 /dev/sdad4 /dev/sdaf6 /dev/sdah8 /dev/sdak /dev/sdam10
----
Some results omitted**
----
[root@roswell root]#

Note that I omitted a large portion of the results because they were huge! Remember that this list is not dependent on the current number of hard drives in the system, but the maximum naming possibilities for any number of drives and partitions. Do not be surprised if your results are rather lengthy as well.

Creating, Mounting, and Configuration New Partitions
Before adding an extra drive, this machine had 2 physical drives. Both of them were named accordingly (sda and sdb) before the new drive was added. The second drive containing the swap partitions was automatically renamed when the new drive was added. Notice the command and output below:


[root@roswell root]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda1 8.3G 2.4G 5.5G 30% /
/dev/sda2 99M 26M 69M 27% /boot
/dev/sdc1 16G 13G 2.3G 85% /export <-- old sdb renamed to sdc by the Linux
none 250M 0 250M 0% /dev/shm
[root@roswell root]#

This command simply lists all currently mounted drives, their names, and space usage. Notice that sdb is not presently mounted. However, we know that it exists otherwise, there would not be an sdc present. I could not add my new drive as sdc because my SCSI hotswap drive cage reserves the first two slots for 1.5" drives. So I was forced to make the new drive sdb because it is a 1.5" drive.

Setting Partitions
You should be fairly familiar with fdisk. The commands are somewhat different than it's DOS equivalent. See the following commands and output:


[root@roswell root]# fdisk /dev/sdb

Command (m for help): m
Command action
a toggle a bootable flag
b edit bsd disklabel
c toggle the dos compatibility flag
d delete a partition
l list known partition types
m print this menu
n add a new partition
o create a new empty DOS partition table
p print the partition table
q quit without saving changes
s create a new empty Sun disklabel
t change a partition's system id
u change display/entry units
v verify the partition table
w write table to disk and exit
x extra functionality (experts only)

Command (m for help):


If there is a problem, and there is no drive associated with /dev/sdb, you will get an error message. Remember, that nothing will actually be executed until you issue a w command. It's always a good idea to read through the variables of your commands. Doing so will ensure that you aren't forgetting anything. Let's get started!


Command (m for help): p

Disk /dev/sdb: 50.0 GB, 50019202560 bytes
255 heads, 63 sectors/track, 6081 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot Start End Blocks Id System

Command (m for help):

If you issue a p command, you will see any partitions that currently exist on the drive. You can see by the output above there are no existing partitions. This drive is un-partitionedd and unformatted. To create a new partition, is the n command.


Command (m for help): n
Command action
e extended
p primary partition (1-4)
p
Partition number (1-4): 1
First cylinder (1-6081, default 1): 1
Last cylinder or +size or +sizeM or +sizeK (1-6081, default 6081): 6081

Command (m for help):

In the output above notice that interval I selected for the cylinders. Using the entire range allows you create one partition across the entire drive. So, in order to create a primary partition on /dev/sdb/ we issued the following commands:
n
(creates a new partition)
p
(creates a primary partition)
1
(the number 1 denotes the partition will be /dev/sdb1)
We can check the partition specifications we just entered by using the p command again.


Command (m for help): p

Disk /dev/sdb: 50.0 GB, 50019202560 bytes
255 heads, 63 sectors/track, 6081 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot Start End Blocks Id System
/dev/sdb1 1 6081 48845601 83 Linux

Command (m for help):


Notice the new partition (highlighted in red). However, we must issue a w command to finalize it. If you messed anything up, you can use the d command and specify which partition you want to delete.


Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.
Syncing disks.
[root@roswell root]#

Formatting
Now that the partition has been created, you need to format the drive. You can format it with almost any file system you wish. However, the most common Linux formats are ext2 and ext3. Ext3 is simply a candy coated version of ext2 that adds a logging feature. You must specify which partition to format by calling the device and partition number like this:


[root@roswell root]# mkfs -t ext3 /dev/sdb1
mke2fs 1.32 (09-Nov-2002)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
6111232 inodes, 12211400 blocks
610570 blocks (5.00%) reserved for the super user
First data block=0
373 block groups
32768 blocks per group, 32768 fragments per group
16384 inodes per group
Superblock backups stored on blocks:
32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208,
4096000, 7962624, 11239424

Writing inode tables: done
Creating journal (8192 blocks): done
Writing superblocks and filesystem accounting information: done

This filesystem will be automatically checked every 38 mounts or
180 days, whichever comes first. Use tune2fs -c or -i to override.
[root@roswell root]#


What did we do there? Using the mkfs (make file system) command, we specified the type (using the -t) ext3 using the device and partition name (/dev/sdb1). You have successfull partitioned and formatted your new drive. Wait, you're not done yet. You will want to mount this partition to make it usable. You will also want this partition to mount automatically when you reboot the machine.


Mounting
In order to automatically mount a partition, you must edit the /etc/fstab file. The fstab file tells Linux where to mount all partitions located within the system. The output below shows the current fstab file before including the newly added drive:


[root@roswell root]# vi /etc/fstab
LABEL=/ / ext3 defaults 1 1
LABEL=/boot /boot ext3 defaults 1 2
none /dev/pts devpts gid=5,mode=620 0 0
LABEL=/export /export ext3 defaults 1 2
none /proc proc defaults 0 0
none /dev/shm tmpfs defaults 0 0
/dev/sdb2 swap swap defaults 0 0
/dev/cdrom /mnt/cdrom udf,iso9660 noauto,owner,kudzu,ro 0 0
/dev/fd0 /mnt/floppy auto noauto,owner,kudzu 0 0

You may notice I viewed this file using vi. Vi is a simple text editor that may or may not be loaded on your Linux system. It is somewhat similar to emacs. In any case, both programs can perform the same task. We will mount the new partition as /media. Remember to create a directory named media, otherwise fstab won't be able to mount the partition. It is shown high-lighted red in the output below:


LABEL=/ / ext3 defaults 1 1
LABEL=/boot /boot ext3 defaults 1 2
none /dev/pts devpts gid=5,mode=620 0 0
LABEL=/export /export ext3 defaults 1 2
none /proc proc defaults 0 0
none /dev/shm tmpfs defaults 0 0
/dev/sdb1 /media ext3 defaults 1 2
/dev/sdb2 swap swap defaults 0 0
/dev/cdrom /mnt/cdrom udf,iso9660 noauto,owner,kudzu,ro 0 0
/dev/fd0 /mnt/floppy auto noauto,owner,kudzu 0 0

Next, issue a simple mount command providing the partition name:


[root@roswell export]# mount /dev/sdb1
[root@roswell export]#

You're all done! You will be able to access the /media folder immediately and after the machine reboots as fstab will automatically re-mount it for you. If you want to verify the partition is successfully present and mounted, use the following commands:


[root@roswell media]# mount
/dev/sda1 on / type ext3 (rw)
none on /proc type proc (rw)
none on /dev/pts type devpts (rw,gid=5,mode=620)
usbdevfs on /proc/bus/usb type usbdevfs (rw)
/dev/sda2 on /boot type ext3 (rw)
/dev/sdc1 on /export type ext3 (rw)
none on /dev/shm type tmpfs (rw)
/dev/sdb1 on /media type ext3 (rw)
[root@roswell media]#

The red line shows our new drive freshly mounted. You can check the space usage if you issue the following command.


[root@roswell media]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda1 8.3G 2.4G 5.5G 30% /
/dev/sda2 99M 26M 69M 27% /boot
/dev/sdc1 16G 13G 2.3G 85% /export
none 250M 0 250M 0% /dev/shm
/dev/sdb1 46G 33M 44G 1% /media

[root@roswell media]#



HAPPY MOUNTING ;)

difference between 32 bit and 64 bit

A common question that pops up from time to time is whether someone who has a 64-bit CPU (such as an AMD64 or an Intel EM64T) should download a 64-bit or 32-bit Linux distribution. Since these processors are capable of running either one at full native speeds, what are the advantages and disadvantages to both? Here I hope to address some common issues.

Speed - Without a scientific set of benchmarks this one is really hard to measure. Some people think one distribution "feels" faster than another while others disagree. Suffice to say that no one has yet to prove scientifically that the 64-bit versions of Linux available today are significantly faster in performance than their 32-bit counterparts. Most "64-bit" versions of software are actually just recompiled versions of the 32-bit code, with no optimization that would take advantage of the new features these chips offer and perhaps boost performance. If you're looking to use 64-bit because you think it will be a major improvement in speed, I would reconsider.

Compatibility - Not all software runs on 64-bit Linux. Although there have been 64-bit native Linux distributions for several years (a year before Microsoft Windows XP64, but I digress), the software community has yet to fully embrace the technology. As of the time this post was written, there is no 64-bit version of the Macromedia Flash Plug-in for your web browser, for instance. WINE and the Java VM have been known to cause problems on some 64-bit installations as well. Not all hardware has 64-bit drivers yet. The two major display card manufacturers (ATI and Nvidia) do have X86_64 versions of their drivers, but they are sadly the exception rather than the norm.

RAM - If you plan on using a machine that has more than 4GB of RAM, you'll need to use the 64-bit version of your distribution because 32-bit operating systems are only able to handle up to 4GB, maximum*. There's just not enough memory addresses for more. This is usually not a problem for desktop users, but it might be a concern for servers or high-end workstations.

The "coolness" factor - As Apple Computer has proven in recent years, there's an awful lot people will do just because something looks or feels "cool". This is perhaps the one reason why some people choose to run 64-bit Linux: it's a neat idea. To some people the idea of running a 64-bit native** operating system on their 64-bit CPU is just too cool to pass up. These people understand the drawbacks to running a bleeding-edge system and accept the extra work involved. If this describes you, more power to you.

So which should I choose? (29 July 2008) Over the last 2 years since I wrote this thread, a lot of progress has been made and I believe at this point that 64-bit Linux distributions are pretty much identical in performance and features as their 32-bit counterparts. I say "pretty much" because there's still no native Flash player. There are ways around that. I've not had issues with Java in 64-bit in recent months, so progress was made there too.

That being said, the point I make in the beginning still stands: although 64-bit Linux distributions are now by and large on-par with their 32-bit brethren, they do not yet surpass them in performance. You're not running at as much of a deficit with 64-bit two years later, but you still don't quite have an advantage either. Now, I think, rather than strongly suggesting 32-bit I could say either will work, but neither has any significant advantage over the other. It's more a matter of personal preference.

* NOTE: The 32-bit Linux kernel can be recompiled to handle up to 64GB of RAM if you're particularly concerned about staying 32-bit.

** NOTE: Although 64-bit Linux distributions do include a natively-compiled Linux kernel and several natively-compiled key applications, not every package in a 64-bit Linux distribution is 64-bit. The 32-bit library files and many 32-bit applications still exist and are used on a regular basis, so the idea that a 64-bit distribution is "native" is really a misnomer.

using pam mysql auth instead of the system user auth

the authenitcatoin server we are going to use is saslauthd

congfig file is : /etc/sysconfig/saslauthd

the mechanism used for checking the file is pam

MECH=pam

since we want auith for our imap clinent we edit this file

/etc/pam.d/imap

username passwdcolumn=password crypt=1 auth sufficient pam_mysql.so user= passwd= host=localhost db=mailusers table=auth usercolumn=uname passwdcolumn=pword crypt=0

account required pam_mysql.so user= passwd= host=localhost db=mailusers table=auth usercolumn=uname passwdcolumn=pword crypt=0

we create the database


we add the tables :

CREATE TABLE `auth` ( `uname` VARCHAR( 30 ) NOT NULL , `pword` VARCHAR( 30 ) NOT NULL , `cid` INT NOT NULL , PRIMARY KEY ( `uname` ) ) ENGINE = MYISAM

restart saslauthd

kernel for xfs reiserfs support

http://landofthefreeish.com/how-to/enable-reiserfs-xfs-jfs-on-rhel5/
see this doc

To install reiserfs using the centosplus repository
refer http://wiki.centos.org/AdditionalResources/Repositories/CentOSPlus

edit /etc/yum.repos.d/CentOS-Base.repo
serch [centosplus]
enabled=1
includepkgs=kernel* jfsutils reiserfs-utils

add exclude=postfix-* in [base] and [update]

yum --enablerepo=centosplus install kernel

how to check fs on centos box

cat /proc/filesystems |grep reiser


possible that kernel module and not yet loaded.

modprobe reiserfs



Sticky Bits, SUID set , SGID set

Here we will discuss about the 3 special attributes other than the common read/write/execute.

Example:

drwxrwxrwt - Sticky Bits - chmod 1777

drwsrwxrwx - SUID set - chmod 4777

drwxrwsrwx - SGID set - chmod 2777


Sticky bit

Sticky bits are mainly set on directories.
If the sticky bit is set for a directory, only the owner of that directory or the owner of a file can delete or rename a file within that directory.

Example:
Consider you have a directory " test ".

chmod it to " 777 ". This gives permissions for all the users to read, write and execute.

chmod +t test

Example: ls -al

drwxrwxrwt 2 a1 a1 4096 Jun 13 2008 .

-rw-rw-r-- 1 a1 a1 0 Jun 11 17:30 1.txt

-rw-rw-r-- 1 b2 b2 0 Jun 11 22:52 2.txt

From the above example a1 is the owner of the test directory.

a1 can delete or rename the files 1.txt and 2.txt.

b2 can delete or rename the file 2.txt only.


SUID - [ Set User ID ]

SUID bit is set for files ( mainly for scripts ).
The SUID permission makes a script to run as the user who is the owner of the script, rather than the user who started it.

Example:
If a1 is the owner of the script and b2 tries to run the same script, the script runs with the ownership of a1.
If the root user wants to give permissions for some scripts to run by different users, he can set the SUID bit for that particular script.
So if any user on the system starts that script, it will run under the root ownership.

Note:
root user much be very carefull with this.




SGID - [ Set Group ID ]

If a file is SGID, it will run with the privileges of the files group owner, instead of the privileges of the person running the program.
This permission set also can make a similar impact. Here the script runs under the groups ownership.

You can also set SGID for directories.
Consider you have given 2777 permission for a directory. Any files created by any users under this directory will come as follows.

Example:

-rw-rw-r-- 1 b2 a1 0 Jun 11 17:30 1.txt

In the above example you can see that the owner of the file 1.txt is b2 and the group owner is a1.
So both b2 and a1 will have access to the file 1.txt.

Now lets make this more intresting and complicated.
Create a directory "test". Chmod it to 2777. Add sticky bit to it.

Example:

mkdir test

chmod 2777 test

chmod +t test

ls -al test

drwxrwsrwt 2 a1 a1 4096 Jun 13 2008 test


From the above permission set you can understand that SGID and sticky bit is set for the folder "test".
Now any user can create files under the test directory.

Example:

drwxrwsrwt 2 a1 a1 4096 Jun 13 2008 .

-rw-rw-r-- 1 b2 a1 0 Jun 11 17:30 1.txt

-rw-rw-r-- 1 c3 a1 0 Jun 11 17:30 2.txt

-rw-rw-r-- 1 d4 a1 0 Jun 11 17:30 3.txt


So all the a1 user has access to all the files under the test directory. He can edit, rename or remove the file.

b2 user has access to 1.txt only, c3 has access to 2.txt only...

If sticky bit was not set for the test directory, any user can delete any files from the test directory, since the test directory has 777 permissions.

But now it not possible.

Example:

If d4 tries to remove 1.txt

rm -f 1.txt

rm: cannot remove `1.txt': Operation not permitted


Important things to know in apache (2)

The number of currently incomming requests can be found using netstat:
netstat -anp | grep :80

Just read the number where the destination address is your servers ip with the port 80.


To find the maximum number of requests apache can handle just look in the httpd.conf file for the MaxClients directive. There should be some other information regarding child processes and how many clients per process each can hold.

http://www.devside.net/articles/apache-performance-tuning


http://virtualthreads.blogspot.com/2006/01/tuning-apache-part-1.html

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