Syntax:-
grep [ option(s) ] pattern [file(s) ]

Example:-1

The basic usage of grep command is to search for a specific string in the specified file as shown below.

[root@localhost ~]# grep root /etc/passwd
root:x:0:0:root:/root:/bin/bash
operator:x:11:0:operator:/root:/sbin/nologin

Above example grep searches the /etc/passwd file for root string and redirected to stdout.

Options
-i This is also a basic usage of the grep. This searches for the given string/pattern case insensitively. So it matches all the words such as “hal”, “HAL” and “The” case insensitively as shown below.

Even you can use Line and, anchors, character classes, wild cards,

[root@localhost ~]# grep -i HAL /etc/passwd
halt:x:7:0:halt:/sbin:/sbin/halt
haldaemon:x:68:68:HAL daemon:/:/sbin/nologin

Example: 2 Searching string in a given file

[root@localhost ~]# grep “root” /etc/passwd
root:x:0:0:root:/root:/bin/bash
operator:x:11:0:operator:/root:/sbin/nologin

Example: 3 Searching string in a multiple files.

[root@localhost ~]# grep “root” /etc/passwd /etc/group
/etc/passwd:root:x:0:0:root:/root:/bin/bash
/etc/passwd:operator:x:11:0:operator:/root:/sbin/nologin
/etc/group:root:x:0:root
/etc/group:bin:x:1:root,bin,daemon
/etc/group:daemon:x:2:root,bin,daemon
/etc/group:sys:x:3:root,bin,adm
/etc/group:adm:x:4:root,adm,daemon
/etc/group:disk:x:6:root
/etc/group:wheel:x:10:root

Example: 4 Regular Expressions in files

? The preceding item is optional and matched at most once.
• * The preceding item will be matched zero or more times.
• + The preceding item will be matched one or more times.
• {n} The preceding item is matched exactly n times.
• {n,} The preceding item is matched n or more times.
• {,m} The preceding item is matched at most m times.
• {n,m} The preceding item is matched at least n times, but not more than m times.

[root@localhost ~]# grep ” *oot” /etc/passwd
root:x:0:0:root:/root:/bin/bash
operator:x:11:0:operator:/root:/sbin/nologin

Example: 5 Searching full word using grep –w

[root@localhost ~]# grep -iw “samba” /etc/samba/smb.conf
# This is the main Samba configuration file. You should read the
# here. Samba has a huge number of configurable options (perhaps too
# For a step to step guide on installing, configuring and using samba,
# read the Samba-HOWTO-Collection. This may be obtained from:

Example : 6

-A option which displays the N lines after the string match.

[root@localhost ~]# grep -A 2 “root” /etc/passwd
root:x:0:0:root:/root:/bin/bash
bin:x:1:1:bin:/bin:/sbin/nologin
daemon:x:2:2:daemon:/sbin:/sbin/nologin

operator:x:11:0:operator:/root:/sbin/nologin
games:x:12:100:games:/usr/games:/sbin/nologin
gopher:x:13:30:gopher:/var/gopher:/sbin/nologin

Example: 6 -B option which displays the N lines before the string match.

[root@localhost ~]# grep -B 2 “root” /etc/passwd
root:x:0:0:root:/root:/bin/bash
–
news:x:9:13:news:/etc/news:
uucp:x:10:14:uucp:/var/spool/uucp:/sbin/nologin
operator:x:11:0:operator:/root:/sbin/nologin

Example: 7 -E option can be used search multiple strings

[root@localhost ~]# ls | grep -E “li|ovo”
linux24
ovo8_linux24.sh
[root@localhost ~]#

Or we can use

[root@localhost ~]# ls | grep ‘li\|ovo’
linux24
ovo8_linux24.sh
[root@localhost ~]#

Example: 8 Below grep command will search string in all files except syslog.log

[root@localhost ~]#grep -r string * | grep -v ‘/\syslog.log/’

NFS Linux

About NFS (Network File System) And Options to Mount

NFS is a client and server architecture based protocol, developed by Sun Microsystems. The main purpose of this protocol is sharing file/file system over network. In general, files/file system sharing between two UNIX machines. User on client computer access remote file system over a network in manner similar to how local storage accessed.

Here we will discuss, how to access NFS share (exports) from the client.

Assuming that HOST A (NFS Server) running NFS service (rpc.mountd, nfsd, rpc.rquotad). Also you can confirm by executing following command on NFS Server.

[root@localhost ~]# service nfs status
rpc.mountd (pid 2919) is running…
nfsd (pid 2916 2915 2914 2913 2910 2909 2908 2907) is running…
rpc.rquotad (pid 2903) is running…
[root@localhost ~]#

Now login to the HOST B (NFS Client) execute following command, to find out shared directories in the NFS Server.

[root@localhost ~]# showmount -e 192.168.1.4
Export list for 192.168.1.4:
/mnt/array1/RHEL5 192.168.1.0/255.255.255.0
/mnt/array1/RHEL632 192.168.1.0/255.255.255.0
[root@localhost ~]#

While entering showmount command, you have to specify IP/Hostname (FQDN) of the NFS Server. After getting exported file system information, you can access by the mount command.

[root@localhost ~]# mount -t nfs 192.168.1.4:/mnt/array1/RHEL5 /data/

Before mounting remote file system, first create mount point, here I have created /data directory and mounted remote file system.

Syntax:

#mount -t vfstype [-o options] NFS Servername:/exporteddirectory /mount point
or
#mount -t nfs -o options host:/remote/export /local/directory

Options:

-t - Option specifies type of the file system that is NFS.
-o intr—this option is used in non reliable network, or network having more network congestion. NFS request will be interrupted when server is not reachable.

Example:

[root@localhost ~]# mount -t nfs -o intr 192.168.1.4:/mnt/array1/RHEL5 /data/
[root@localhost ~]# mount | grep -i intr
192.168.1.4:/mnt/array1/RHEL5 on /data type nfs (rw,intr,addr=192.168.1.4)

Hard – if hard option is specified during nfs mount, user cannot terminate the process waiting for NFS communication to resume.

Example:

[root@localhost ~]# mount -t nfs -o hard 192.168.1.4:/mnt/array1/RHEL5 /data/
[root@localhost ~]# mount | grep -i hard
192.168.1.4:/mnt/array1/RHEL5 on /data type nfs (rw,hard,addr=192.168.1.4)

Soft- if soft option is specified during nfs mount, user will get error alert when NFS server is not reachable.

Example:

[root@localhost ~]# mount -t nfs -o soft 192.168.1.4:/mnt/array1/RHEL5 /data/
[root@localhost ~]# mount | grep -i soft
192.168.1.4:/mnt/array1/RHEL5 on /data type nfs (rw,soft,addr=192.168.1.4)
[root@localhost ~]#

Nfsvers=value– if this option is specified during nfs mount NFS client uses particular NFS protocol version to communicate.

Example:

[root@localhost ~]# mount -t nfs -o nfsvers=3 192.168.1.4:/mnt/array1/RHEL5 /data/
[root@localhost ~]# mount | grep -i nfsvers
192.168.1.4:/mnt/array1/RHEL5 on /data type nfs (rw,nfsvers=3,addr=192.168.1.4)

Tcp or UDP: As said above, NFS is client and server architecture based protocol and it can be used transport layer as TCP and UDP both depend upon the application requirement.

Example: TCP

[root@localhost ~]# mount -t nfs -o tcp 192.168.1.4:/mnt/array1/RHEL5 /data/
[root@localhost ~]# mount | grep -i tcp
192.168.1.4:/mnt/array1/RHEL5 on /data type nfs (rw,tcp,addr=192.168.1.4)

Example: UDP

[root@localhost ~]# mount -t nfs -o udp 192.168.1.4:/mnt/array1/RHEL5 /data/
[root@localhost ~]# mount | grep -i udp
192.168.1.4:/mnt/array1/RHEL5 on /data type nfs (rw,udp,addr=192.168.1.4)

Iscsi Storage Network

Here I am trying to explain Equallogic Lun configuration on Redhat Linux 5 version. Linux Iscsi Storage Lun Mapping is much simpler on Equallogic Storage Array. Free Open Isci tool is used as the iscsi initiator. Once installed you can use iscsiadm command to configure the Lun. Dell recommends to configure iscsi on redhat 5 or above version.

First you should create volumes on the storage group interface manager and then needs to maps those Luns to server. You need to mention either iscsi initiator name or IP address to map the Lun to the server(host). If you need any authentication you can use chap. Now you can move to Linux host for further iscsi configuration.

Show current installed redhat version and update

[root@BobTestBox ~]# cat /etc/redhat-release
Red Hat Enterprise Linux Server release 5.7 (Tikanga)

Display Architecture

[root@BobTestBox ~]# getconf LONG_BIT
64

Check isci initiator installed or not (You need iscsi-initiator-utils-6.2.0.742-0.6.el5 or greater)

[root@BobTestBox ~]# rpm -qa | grep -i iscsi
iscsi-initiator-utils-6.2.0.872-10.el5

Display interfaces and IP address details

[root@BobTestBox ~]# ifconfig -a | more
eth0 Link encap:Ethernet HWaddr 00:50:56:AB:00:E7
inet addr:172.28.*.* Bcast:172.28.12.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:2503 errors:0 dropped:0 overruns:0 frame:0
TX packets:838 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:196784 (192.1 KiB) TX bytes:98212 (95.9 KiB)

eth1 Link encap:Ethernet HWaddr 00:50:56:AB:00:E8
inet addr:172.28.*.* Bcast:172.28.40.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:4237 errors:0 dropped:0 overruns:0 frame:0
TX packets:3807 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:966177 (943.5 KiB) TX bytes:359247 (350.8 KiB)

eth2 Link encap:Ethernet HWaddr 00:50:56:AB:01:00
inet addr:172.28.*.* Bcast:172.28.40.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:4387 errors:0 dropped:0 overruns:0 frame:0
TX packets:3960 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:894415 (873.4 KiB) TX bytes:384013 (375.0 KiB)

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:10 errors:0 dropped:0 overruns:0 frame:0
TX packets:10 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:660 (660.0 b) TX bytes:660 (660.0 b)

Creating the interface files for MPIO

[root@BobTestBox ~]# iscsiadm -m iface -I eth1 -o new
New interface eth1 added

[root@BobTestBox ~]# iscsiadm -m iface -I eth2 -o new
New interface eth2 added

Updating the interface name for each port

[root@BobTestBox ~]# iscsiadm -m iface -I eth1 -o update -n iface.net_ifacename -v eth1
eth1 updated.

[root@BobTestBox ~]# iscsiadm -m iface -I eth2 -o update -n iface.net_ifacename -v eth2
eth2 updated.

[root@BobTestBox ~]# cat /var/lib/iscsi/ifaces/eth1
# BEGIN RECORD 2.0-872
iface.iscsi_ifacename = eth1
iface.net_ifacename = eth1
iface.transport_name = tcp
# END RECORD
[root@localhost ~]# cat /var/lib/iscsi/ifaces/eth2
# BEGIN RECORD 2.0-872
iface.iscsi_ifacename = eth2
iface.net_ifacename = eth2
iface.transport_name = tcp
# END RECORD

Iscsi target Discovering using iscsiadm command

[root@BobTestBox ~]# iscsiadm -m discovery -t st -p 172.28.*.*:3260
172.28.*.*:3260,1 iqn.2001-05.com.equallogic:0-8a0906-a146b2a07-57858e634784f7b0-bobrhel
172.28.*.*:3260,1 iqn.2001-05.com.equallogic:0-8a0906-a146b2a07-57858e634784f7b0-bobrhel

Logging into target ( You have option to login individually also)

[root@BobTestBox ~]# iscsiadm -m node -l
Logging in to [iface: eth2, target: iqn.2001-05.com.equallogic:0-8a0906-a146b2a07-57858e634784f7b0-bobrhel, portal: 172.28.*.*,3260]
Logging in to [iface: default, target: iqn.2001-05.com.equallogic:0-8a0906-a146b2a07-57858e634784f7b0-bobrhel, portal: 172.28.*.*,3260]
Logging in to [iface: eth1, target: iqn.2001-05.com.equallogic:0-8a0906-a146b2a07-57858e634784f7b0-bobrhel, portal: 172.28.*.*,3260]
Login to [iface: eth2, target: iqn.2001-05.com.equallogic:0-8a0906-a146b2a07-57858e634784f7b0-bobrhel, portal: 172.28.*.*,3260] successful.
Login to [iface: default, target: iqn.2001-05.com.equallogic:0-8a0906-a146b2a07-57858e634784f7b0-bobrhel, portal: 172.28.*.*,3260] successful.
Login to [iface: eth1, target: iqn.2001-05.com.equallogic:0-8a0906-a146b2a07-57858e634784f7b0-bobrhel, portal: 172.28.*.*,3260] successful.
[root@BobTestBox ~]#

Display scsi attached device

[root@BobTestBox ~]# cat /proc/scsi/scsi
Attached devices:
Host: scsi0 Channel: 00 Id: 00 Lun: 00
Vendor: VMware Model: Virtual disk Rev: 1.0
Type: Direct-Access ANSI SCSI revision: 02
Host: scsi7 Channel: 00 Id: 00 Lun: 00
Vendor: EQLOGIC Model: 100E-00 Rev: 5.2
Type: Direct-Access ANSI SCSI revision: 05
Host: scsi6 Channel: 00 Id: 00 Lun: 00
Vendor: EQLOGIC Model: 100E-00 Rev: 5.2
Type: Direct-Access ANSI SCSI revision: 05
[root@BobTestBox ~]#

Below command will display Iscsi session details

[root@BobTestBox ~]# iscsiadm -m session
tcp: [6] 172.28.*.*:3260,1 iqn.2001-05.com.equallogic:0-8a0906-a146b2a07-57858e634784f7b0-bobrhel
tcp: [7] 172.28.*.*:3260,1 iqn.2001-05.com.equallogic:0-8a0906-a146b2a07-57858e634784f7b0-bobrhel
[root@BobTestBox ~]#

Display Disk details

[root@BobTestBox ~]# fdisk -l

Disk /dev/sda: 5368 MB, 5368709120 bytes
255 heads, 63 sectors/track, 652 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot Start End Blocks Id System
/dev/sda1 * 1 574 4610623+ 83 Linux
/dev/sda2 575 652 626535 82 Linux swap / Solaris

Disk /dev/dm-0: 1085 MB, 1085276160 bytes
255 heads, 63 sectors/track, 131 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Disk /dev/dm-0 doesn’t contain a valid partition table

Disk /dev/sde: 1085 MB, 1085276160 bytes
34 heads, 61 sectors/track, 1022 cylinders
Units = cylinders of 2074 * 512 = 1061888 bytes

Disk /dev/sde doesn’t contain a valid partition table

Disk /dev/sdf: 1085 MB, 1085276160 bytes
34 heads, 61 sectors/track, 1022 cylinders
Units = cylinders of 2074 * 512 = 1061888 bytes

Disk /dev/sdf doesn’t contain a valid partition table
[root@BobTestBox ~]#

Checking whether Equallogic Hit installed ( I have already installed HIT Kit 1.0.0- #rpm –ivh equallogic-host-tools-1.0.0-1.el5.x86_64.rpm )

[root@BobTestBox ~]# rpm -qa | grep -i equa
equallogic-host-tools-1.0.0-1.el5

Hit requires dkms 1.95 (Dynamic kernel module support) installed. ( I have already installed dkms – #rpm –ivh dkms-1.95.32-1.noarch.rpm )

[root@BobTestBox ~]# rpm -qa | grep -i dkms
dkms-1.95.32-1

Dkms module can be download from http://linux.dell.com/dkms/testing/permalink/

Restarting EHCMD service (dell multipath module )

[root@BobTestBox ~]# /etc/init.d/ehcmd restart
Stopping ehcmd: [FAILED]
Starting ehcmd: [ OK ]

Restarting Multipath deamon ( You can set alias ,uuid , device details , blacklist node in multhipath.conf file before restarting)

[root@BobTestBox ~]# /etc/init.d/multipathd restart
Stopping multipathd daemon: [FAILED]
Starting multipathd daemon: [ OK ]
[root@BobTestBox ~]#

Display multhipath details

[root@BobTestBox ~]# multipath -ll
Bob_rhel_lun () dm-0 EQLOGIC,100E-00
[size=1.0G][features=1 queue_if_no_path][hwhandler=0][rw]
\_ round-robin 0 [prio=2][enabled]
\_ 3:0:0:0 sdc 8:32 [active][ready]
\_ 1:0:0:0 sdd 8:48 [active][ready]
[root@BobTestBox ~]#

Device mapper target device status

[root@BobTestBox ~]# dmsetup ls –target=multipath
Bob_rhel_lun (253, 0)
[root@BobTestBox ~]#

Mounting the the filesystem. I have already formated the filesystem using mkfs command (mkfs.ext3 /dev/mapper/Bob_rhel_lun)

[root@BobTestBox ~]# mount /dev/mapper/Bob_rhel_lun /data

Display disk usage

[root@BobTestBox ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda1 4.3G 2.7G 1.5G 66% /
tmpfs 502M 0 502M 0% /dev/shm
/dev/mapper/Bob_rhel_lun 1019M 34M 934M 4% /data
[root@BobTestBox ~]#

For persistence on reboot , added mount point to fstab file

[root@BobTestBox ~]# cat /etc/fstab
LABEL=/ / ext3 defaults 1 1
tmpfs /dev/shm tmpfs defaults 0 0
devpts /dev/pts devpts gid=5,mode=620 0 0
sysfs /sys sysfs defaults 0 0
proc /proc proc defaults 0 0
LABEL=SWAP-sda2 swap swap defaults 0 0
/dev/mapper/Bob_rhel_lun /data ext3 defaults 0 0
[root@BobTestBox ~]#

LoadModule auth_module /usr/lib/apache/1.3/mod_session.so

Please note that your Apache server must configure for Dynamic Shared Objects (DSOs). Let us assume you have downloaded the module called mymodule.c and you would like to compile and use this module, then you can use Apache apxs utility to compile and install this module:

Build and install a third-party Apache module, say mod_foo.c, into its own DSO mod_foo.so outside of the Apache source tree using apxs:

# apxs -c mymodule.c
# apxs -i -a -n mymodule mymodule.la

Then open your httpd.conf file and add mymodule using top LoadModule Directive:

# vi httpd.conf

Append following line to server config context (this means that the directive may be used in the server configuration files (e.g., httpd.conf), but not within any or containers. It is not allowed in .htaccess files at all).

LoadModule mymodule /usr/lib/httpd/modules/mymodule.so

Below example show how to enable mod_deflate module.

LoadModule deflate_module modules/mod_deflate.so

Append following configuration directive:

AddOutputFilterByType DEFLATE text/html text/plain text/xml
….
…

Above line only compress html and xml files. Here is the configuration from one of my production box:

…
…
AddOutputFilterByType DEFLATE text/plain
AddOutputFilterByType DEFLATE text/xml
AddOutputFilterByType DEFLATE application/xhtml+xml
AddOutputFilterByType DEFLATE text/css
AddOutputFilterByType DEFLATE application/xml
AddOutputFilterByType DEFLATE image/svg+xml
AddOutputFilterByType DEFLATE application/rss+xml
AddOutputFilterByType DEFLATE application/atom_xml
AddOutputFilterByType DEFLATE application/x-javascript
AddOutputFilterByType DEFLATE application/x-httpd-php
AddOutputFilterByType DEFLATE application/x-httpd-fastphp
AddOutputFilterByType DEFLATE application/x-httpd-eruby
AddOutputFilterByType DEFLATE text/html
…
…

Close and save the file. Next restart apache web server. All of the above extension file should compressed by mod_deflate:
# /etc/init.d/httpd restart

You can also specify specific directory and enabling compression only for the html files. For example /static/help/ directory:

AddOutputFilterByType DEFLATE text/html

In real life, there are issues with compressing other types of files such as mp3 or images. If you don’t want to compress images or mp3 files, add following to your configuration:
SetOutputFilter DEFLATE
SetEnvIfNoCase Request_URI \.(?:gif|jpe?g|png)$ no-gzip dont-vary
SetEnvIfNoCase Request_URI \.(?:exe|t?gz|zip|bz2|sit|rar)$ no-gzip dont-vary
SetEnvIfNoCase Request_URI \.pdf$ no-gzip dont-vary
SetEnvIfNoCase Request_URI \.avi$ no-gzip dont-vary
SetEnvIfNoCase Request_URI \.mov$ no-gzip dont-vary
SetEnvIfNoCase Request_URI \.mp3$ no-gzip dont-vary
SetEnvIfNoCase Request_URI \.mp4$ no-gzip dont-vary
SetEnvIfNoCase Request_URI \.rm$ no-gzip dont-vary

Options Indexes FollowSymLinks
bla bla bla

To disable directory listing for that directory REMOVE the ‘Indexes’
option. Also, you can use ‘-Indexes’ for that and, sure, you can make a
new entry for a specific directory

OR

One of the “must do’s” on setting a secure apache webserver environment is to disable directory browsing. As a default Apache will be compiled with this option enabled, but its always a good idea to get rid of this setting unless its really necessary. If you have some basic knowledge of vi editor follow this steps

If you are on an RPM installation of Apache (which i dont really recommend) you will find the apache configuration file probably here:

/etc/httpd/conf/httpd.conf

If you are using apache from the source tar balls ( like real men ) probably you will find the configuration file here:

/usr/local/apache/conf/httpd.conf

Using an editor like vi , edit the httpd.conf file and scroll until you find a line like this:

Options All Indexes FollowSymLinks MultiViews

To disable directory browsing carefully remove the line that says: Indexes and leave the line like this:

Options All FollowSymLinks MultiViews

Restart your apache webserver and thats all.

vi /etc/httpd/conf/httpd.conf

————————
————————-
——————————
NameVirtualHost 67.159.54.145:80
NameVirtualHost 67.159.54.146:80

ServerName sample.com
ServerAlias www.sample.com
DocumentRoot /home/sample/public_html

ServerName techside.com
ServerAlias www.techside.com
DocumentRoot /home/techside/public_html

=============================================================
hash all lines in this file other wise default page will display

/etc/httpd/conf.d/welcome.conf

#
# This configuration file enables the default “Welcome”
# page if there is no default index page present for
# the root URL. To disable the Welcome page, comment
# out all the lines below.
#
#
# Options -Indexes
# ErrorDocument 403 /error/noindex.html
#

Create a new password file

Following command will creates a new file and stores a record in it for user jerry. The user is prompted for the password. If the file exists and cannot be read, or cannot be written, it is not altered and htpasswd will display a message and return an error status.

# htpasswd -c /home/pwww/.htpasswd user

Change or update password

To add or modifies the password for user tom, enter:

# htpasswd /home/pwww/.htpasswd-users tom

The user is prompted for the password.

————————————————————————————————————————————–
/etc/init.d/httpd restart: httpd not running, trying to start
[Tue May 6 01:31:31 2008] [warn] module bwlimited_module is already loaded, skipping
[Tue May 6 01:31:31 2008] [warn] module php5_module is already loaded, skipping
/etc/init.d/httpd: line 83: 1044 Segmentation fault (core dumped) $HTTPD
/etc/init.d/httpd restart: httpd could not be started

————————————————————————————————————————————–

One of the reasons why this could happen is the use of Resin modules along with apache. Resin modules act as a fast servlet runner for apache. It acts as a separate layer that speeds up Java servlet handling. Normally, apache doesen’t support JSP pages, Resin modules serves this function too.

Once you come across such an error, follow the steps below to bring apache back online.

1) cd /usr/local/apache/logs

2) Remove the following:

rm -rf ssl*
rm -rf core.*
rm sess*

3) Try to restart apache using apachectl and and /etc/init.d/httpd. Examine the core dump file and see if you can find out
which module is causing the module.

4) If you cannot find out which particular module is causing the issue, find out the php modules that are compiled into
apache using php -m.

5) php -m will list out the modules. You can search for each module in the httpd.conf file. Comment out each module and then try restarting apache . (use /etc/init.d/httpd startssl)Obviously, this is a trial and error method and can consume a little more time. But it is effective. By this way, we can find out which module is causing the trouble.

For example, lets say the Resin module is causing the problem. Then search for “resin” in httpd.conf. You should find something like
“ResinConfigServer 127.0.0.1 6802″ comment out the line and restart apache using /etc/init.d/httpd startssl. This should fix the problem.

The option ServerType specifies how Apache should run on the system. You can run it from the super-server inetd, or as standalone daemon. It’s highly recommended to run Apache in standalone type for better performance and speed.

ServerRoot “/etc/httpd”

The option ServerRoot specifies the directory in which the configuration files of the Apache server lives. It allows Apache to know where it can find its configuration files when it starts.

PidFile /var/run/httpd.pid

The option PidFile specifies the location where the server will record the process id of the daemon when it starts. This option is only required when you configure Apache in standalone mode.

ResourceConfig /dev/null

The option ResourceConfig specifies the location of the old srm.conf file that Apache read after it finished reading the httpd.conf file. When you set the location to /dev/null, Apache allows you to include the content of this file in httpd.conf file, and in this manner, you have just one file that handles all your configuration parameters for simplicity.

AccessConfig /dev/null

The option AccessConfig specifies the location of the old access.conf file that Apache read after it finished reading the srm.conf file. When you set the location to /dev/null, Apache allows you to include the content of this file in httpd.conf file, and in this manner, you have just one file that handles all your configuration parameters for simplicity.

Timeout 300

The option Timeout specifies the amount of time Apache will wait for a GET, POST, PUT request and ACKs on transmissions. You can safely leave this option on its default values.

KeepAlive On

The option KeepAlive, if set to On, specifies enabling persistent connections on this web server. For better performance, it’s recommended to set this option to On, and allow more than one request per connection.

MaxKeepAliveRequests 0

The option MaxKeepAliveRequests specifies the number of requests allowed per connection when the KeepAlive option above is set to On. When the value of this option is set to 0 then unlimited requests are allowed on the server. For server performance, it’s recommended to allow unlimited requests.

KeepAliveTimeout 15

The option KeepAliveTimeout specifies how much time, in seconds, Apache will wait for a subsequent request before closing the connection. The value of 15 seconds is a good average for server performance.

MinSpareServers 16

The option MinSpareServers specifies the minimum number of idle child server processes for Apache, which is not handling a request. This is an important tuning parameter regarding the performance of the Apache web server. For high load operation, a value of 16 is recommended by various benchmarks on the Internet.

MaxSpareServers 64

The option MaxSpareServers specifies the maximum number of idle child server processes for Apache, which is not handling a request. This is also an important tuning parameter regarding the performance of the Apache web server. For high load operation, a value of 64 is recommended by various benchmarks on the Internet.

StartServers 16

The option StartServers specifies the number of child server processes that will be created by Apache on start-up. This is, again, an important tuning parameter regarding the performance of the Apache web server. For high load operation, a value of 16 is recommended by various benchmarks on the Internet.

MaxClients 512

The option MaxClients specifies the number of simultaneous requests that can be supported by Apache. This too is an important tuning parameter regarding the performance of the Apache web server. For high load operation, a value of 512 is recommended by various benchmarks on the Internet.

MaxRequestsPerChild 100000

The option MaxRequestsPerChild specifies the number of requests that an individual child server process will handle. This too is an important tuning parameter regarding the performance of the Apache web server.

User www

The option User specifies the UID that Apache server will run as. It’s important to create a new user that has minimal access to the system, and functions just for the purpose of running the web server daemon.

Group www

The option Group specifies the GID the Apache server will run as. It’s important to create a new group that has minimal access to the system and functions just for the purpose of running the web server daemon.

DirectoryIndex index.htm index.html index.php index.php3 default.html index.cgi

The option DirectoryIndex specifies the files to use by Apache as a pre-written HTML directory index. In other words, if Apache can’t find the default index page to display, it’ll try the next entry in this parameter, if available. To improve performance of your web server it’s recommended to list the most used default index pages of your web site first.

Include conf/mmap.conf

The option Include specifies the location of other files that you can include from within the server configuration files httpd.conf. In our case, we include the mmap.conf file located under /etc/httpd/conf directory. This file mmap.conf maps files into memory for faster serving. See the section on Optimizing Apache for more information.

HostnameLookups Off

The option HostnameLookups, if set to Off, specifies the disabling of DNS lookups. It’s recommended to set this option to Off in order to save the network traffic time, and to improve the performance of your Apache web server.