Issues that are encountered in web hosting

When tried to change passwd from WHM, the following error is displayed.

Error
The password for “user” could not be changed because:

Check the error in log file: /usr/local/cpanel/logs/error_log
You will find similar error as shown below.

=============================================================

Can’t locate Crypt/PasswdMD5/XS.pm in @INC (@INC contains:
/scripts /usr/lib64/perl5/site_perl/5.8.8/x86_64-linux-thread-multi
/usr/lib/perl5/site_perl/5.8.8 /usr/lib/perl5/site_perl
/usr/lib64/perl5/vendor_perl/5.8.8/x86_64-linux-thread-multi
/usr/lib/perl5/vendor_perl/5.8.8 /usr/lib/perl5/vendor_perl
/usr/lib64/perl5/5.8.8/x86_64-linux-thread-multi
/usr/lib/perl5/5.8.8 .) at /scripts/cPScript/CheckPass/UNIX.pm line 6.
BEGIN failed–compilation aborted at /scripts/cPScript/CheckPass/UNIX.pm line 6.
Compilation failed in require at /scripts/cPScript/CheckPass.pm line 6.
BEGIN failed–compilation aborted at /scripts/cPScript/CheckPass.pm line 6.
Compilation failed in require at /scripts/realchpass line 16.
BEGIN failed–compilation aborted at /scripts/realchpass line 16.

=============================================================

Fix:

ssh into the server with root login credentials.
# /scripts/perlinstaller Crypt::PasswdMD5
Check if the issue still persists.

Then, let’s try fixing the problem without rebuilding Perl or changing any system configuration files. Run:

# /scripts/checkperlmodules
# service cpanel restart

Try changing the password again. If you’re still getting the error, it’s likely that the cPanel Perl installation was overwritten by an updated Perl RPM either manually or by yum. Let’s make sure Perl is left up to cPanel and check if perl automatic perl update is disabled in cPanel and excluded from yum list.

# grep allowperlupdates /var/cpanel/cpanel.config

If you see allowperlupdates=1 you’ve enabled “Allow Perl updates from RPM-based linux vendors” in WHM under Tweak Settings -> System. Return to WHM and uncheck this option then click the “Save” button.

In /etc/yum.conf, check if perl is present in exclude and intall the pearl module.
exclude=apache* bind-chroot courier* dovecot* exim* httpd* mod_ssl* mysql* nsd* perl* php*

Steps to install the pearl module.
First check the current version of Perl
# perl -v
If the older version of Perl is running on server, you get an output something like,
This is perl, v5.8.7 built for i686-linux
Upgrade perl on the Cpanel server
1) Download the latest perl installer from cPanel site.
# wget http://layer1.cpanel.net/perl588installer.tar.gz

2) Untar the file.
# tar -zxvf perl588installer.tar.gz

3) Change the directory to perl588installer.
# cd perl588installer

4) Now run the installer file.
# ./install

5) Check perl modules.
# /scripts/checkperlmodules

6) Force a cPanel update.
# /scripts/upcp –force

****************************************************************************************************************

How to locate mysql log file in the server.

* Check whether the mysql log file is present in /var/log such as /var/log/mysqld.log

* Usually, the mysql log file is present in /var/lib/mysql for cPanel servers. Kindly follow the steps to find the log file

======================================================================================================
root@server1 [/var/lib/mysql]# top -c | grep mysql
17545 mysql 15 0 427m 209m 5176 S 3.9 2.6 266:16.79 /usr/sbin/mysqld –basedir=/ –datadir=/var/lib/mysql –user=mysql –pid-file=/var/lib/mysql/server1.abc.com
======================================================================================================

Find the hostname of the server.
=======================
root@server1 [~]# hostname
server1.abc.com
=======================

We need to find the presently running mysql log file in the server. Usually, mysql log file will be associated with the hostname.

=======================================================
root@server1 [/var/lib/mysql]# ls -l | grep -i server1.abc.com
-rw-rw—-   1 mysql mysql  48495912 Aug 19 16:46 server1.abc.com.err
-rw-rw—-   1 mysql mysql     41720 May 18  2009 SERVER1.ABC.COM.err
-rw-rw—-   1 mysql mysql         6 Aug 19 16:46 server1.abc.com.pid
-rw-rw—-   1 mysql mysql         6 May 18  2009 SERVER1.ABC.COM.pid
=======================================================

From the above code, we find that server1.abc.com.err is used recently (checking with date). Therefore, server1.abc.com.err is the log file. To confirm it further, kindly check the process ID of server1.abc.com.pid with that of mysql process ID.

==========================================
root@server1 [/var/lib/mysql]# cat server1.abc.com.pid
17545
==========================================

The mysql log file displayed below.

==============================================================================
root@server1 [/var/lib/mysql]# vi server1.abc.com.err

090503 04:31:43 mysqld started
InnoDB: The first specified data file ./ibdata1 did not exist:
InnoDB: a new database to be created!
090503 4:31:43 InnoDB: Setting file ./ibdata1 size to 10 MB
InnoDB: Database physically writes the file full: wait…
090503 4:31:43 InnoDB: Log file ./ib_logfile0 did not exist: new to be created
InnoDB: Setting log file ./ib_logfile0 size to 5 MB
InnoDB: Database physically writes the file full: wait…
090503 4:31:43 InnoDB: Log file ./ib_logfile1 did not exist: new to be created
InnoDB: Setting log file ./ib_logfile1 size to 5 MB
InnoDB: Database physically writes the file full: wait…
InnoDB: Doublewrite buffer not found: creating new
InnoDB: Doublewrite buffer created
InnoDB: Creating foreign key constraint system tables
InnoDB: Foreign key constraint system tables created
090503 4:31:43 InnoDB: Started; log sequence number 0 0
090503 4:31:43 [Note] /usr/sbin/mysqld: ready for connections.
Version: ‘5.0.67-community’ socket: ‘/var/lib/mysql/mysql.sock’ port: 3306 MySQL Community Edition (GPL)
090503 4:31:46 [Note] /usr/sbin/mysqld: Normal shutdown

090503 4:31:46 InnoDB: Starting shutdown…
090503 4:31:47 InnoDB: Shutdown completed; log sequence number 0 43655
090503 4:31:47 [Note] /usr/sbin/mysqld: Shutdown complete

090503 04:31:47 mysqld ended
==============================================================================

***********************************************************************************

The “latest visitor” log in the stats of the cpanel is weird and not getting updated.

Error: Raw Access log contain only term “combined”, liked combined combined combined……………………

Fix:
Check if the format provided below is correct in the apache configuration file where version is Apache/2.2.15.
=======================================================================
<IfModule log_config_module>
LogFormat “%h %l %u %t \”%r\” %>s %b \”%{Referer}i\” \”%{User-Agent}i\”" combined
LogFormat “%h %l %u %t \”%r\” %>s %b” common

CustomLog logs/access_log common

<IfModule logio_module>
LogFormat “%h %l %u %t \”%r\” %>s %b \”%{Referer}i\” \”%{User-Agent}i\” %I %O” combinedio

</IfModule>

</IfModule>
=====================================================================

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mod_php explained

Preface

Like in the case of all apache modules, you can either compile PHP as a static module or compile it as a dynamic module.  In the case of static module , you  can’t perform any modification for the module without recompiling the binary to which it is attached.  For eg.  you can’t add ssl support for the mod_php without re-compiling apache as a whole. And any failure in the compilation may cause downtime for the entire webserver also, including plain html support.

The advantage is that it provides a faster  performance, because the module is initialized  whenever the apache binary is started.

In the case of a dynamic mod_php installation, the necessary modifications or module additions can be done by recompiling the module alone. There is no need to recompile the Apache as the mod_php is not linked with the binary of apache.  But since the webserver loads the module on the fly, it needs to load, initialize and then execute the module.  So it can create some level of slowness while processing php pages.

How does mod_php work?

When PHP  is loaded into Apache as a module (using mod_php), each Apache process will contain an instance of mod_php or PHP interpreter also.   The interpreter comes with a bundle of libraries we enabled during compilation and each  process can make use of these libraries to process the requests. This means that the Apache process that just started  to load a simple HTML page  too will contain a PHP interpreter with all assigned libraries which inturn means resource consumption.

When the webserver gets an HTTP request. The  request header  contains the path to the requested document

e.g. access.log:    xx.xx.xx.xx – - [22/June/2010:21:14:53 -0700] “GET /info.php?=PHPE9568F35-D428-11d2-A769-00AA001ACF42 HTTP/1.1″ 200 2146 “http://domain.com/info.php” “Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.1.7) Gecko/20100106 Ubuntu/9.10 (karmic) Firefox/3.5.7″

1. The request will be redirected to the document root of the domain and then to the file “info.php” , if it fails then the corresponding error message will be given.

2. The info.php file is to be processed. It follows the following steps

Normally every httpd.conf file will have an entry like this

AddType application/x-httpd-php .php5 .php4 .php

It instructs the webserver that the files with extension .php ,.php4,.ph5 are of PHP mime type . The TypesConfig directive sets the location of the MIME types configuration file. This file controls what Internet media types are sent to the client for  given file extension(s).  Sending the correct media type to the client  is important so they know how to handle the content of the file.

root@new [/usr/local/apache/conf]# cat mime.types | grep x-httpd-php
application/x-httpd-php-source          phps
application/x-httpd-php          php php3 php4 php5 php6
root@new [/usr/local/apache/conf]#

Here we can see that the Mime type to be used for files with extension .php  is application/x-httpd-php , while the file with .phps is to be mapped to the php mime type application/x-httpd-php-source .

The webserver identifies that the requested file is of Mime type x-httpd-php.

To handle or process it , the apache has to load the corresponding module. Since it is a php type , the module mod_php will be loaded and it will execute the file.

Since apache is a HTTP server. It gets the HTTP requests and answers with the HTML code.  So the mod_php will execute the commands within php flag and creates the HTML page dynamically and send it back to the client – internet browser which sent HTTP request.

Security concerns / Implications

You can see that  every request or execution of a php file through web is initiated by the webserver. So the webserver acts as the parent of every php execution through web. It imposes a great security threat. Since apache is being executed as an apache  user, all process will be owned by that user. By default  it is “nobody” or “apache”.  Let me try to explain.

If your  web application performs some operations in the db, unless that database (eg: a flat text DB) has built-in access control, you will have to make the database accessible to the “nobody” user. This means a malicious script could access and modify the database, even without a username and password.  Such can be the case with various configuration files too.  Unless you protect these directories or applications with necessary authorization techniques like .htaccess, session control etc. There is a high possibility of attack through webapplication.

Another dangerous issue is of root escalation. If the webserver has a bug, by exploiting that bug, a malicious user can gain some root privileges or escalated to root. Its quite alarming situation as an escalated apache user can do any sort of  actions without any level of authentication.

Also it is difficult to identify the script which performs the malicious activity as all php scripts will be executed as “nobody”

Since PHP applications are executed as web server user, you need to give access and write permissions for the directories wherever the application  is supposed to be working. Sometimes you may be forced to give 777 permissions and it invites lot of attacks.

The files created by php applications will be owned by user “nobody” . So the user will not be able to delete the files unless it is done through another php application. Otherwise he needs to contact the server admin to get the same.

As a security measure, we may be forced to block mails from “nobody” users . But it can create mails generated from php applications being blocked in the server. Various php applications widely used for spamming . So some servers are configured to block mails from nobody users. This creates inconvenience to users.

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The very basics of a PHP – Not for the developers or sysadmins but for a tech support engineer

What is PHP?

PHP is similar to many other scripting languages like perl, python etc. But unlike perl and python what makes it stand apart is, its adaptability and power to be used as both command line and server side scripting.  I hear Yahoo’s mail runs on PHP.

I shall try to explain you the difference by executing the same file on different modes. Don’t expect too much from this post.

Command Line (CLI)

PHP Command Line Interface or PHP CLI  as the name implies,  is a way of using PHP in the system command line, like below. (Read the rest of this entry…)

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Source compilation of Apache

Basics of Compilation of Apache with PHP

Here we are going to install apache using the source only. The choice of Operating System here is Linux (distro: Centos). The procedure we follow here will lead to a simple apache installation for dynamic loading of php. PHP will be installed as a module to apache. With a little bit of patience and time, all the necessary modules can be installed with apache. I will be giving a brief idea about the installation of the other modules later.
The basics of installation from the source involves mainly three simple steps (assuming you are lucky):

./configure
make
make install

./configure creates the MAKEFILE on the fly. We can provide the necessary options to configure. To list the available options in the configuring step use

./configure --help

–prefix=/path/… mentions where the executable and its files are installed. If not mentioned it takes the default values.
–enable-[Feature] will enable the specified Feature in apache as it is being built. We are only interested in the DSO capability and hence we enable it with: –enable-so

As a convention we always keep the source code tar ball inside a directory in /usr/src/, thus source installation begins in this directory.

Apache Compilation

Download the required source tar ball of the apache you would like to compile. Here I am installing httpd-2.0.63 from http://httpd.apache.org/download.cgi#apache20. I save it in the /usr/src/ folder.

cd /usr/src/
wget http://www.bizdirusa.com/mirrors/apache/httpd/httpd-2.0.63.tar.gz

This will result in the generation of the file httpd-2.0.63.tar.gz

tar -xzf httpd-2.0.63.tar.gz

This will result in the creation of the directory httpd-2.0.63. Next enter inside this directory and execute the ./configure command.

cd httpd-2.0.63
./configure --prefix=/usr/local/webserver --enable-so

We are installing apache inside /usr/local/webserver and enable DSO to run php as a module to apache. During this process we may get a lot of errors. We resolve these by manually installing the unresolved dependencies either by obtaining their rpms or by using yum. Normally the first dependency we will get to resolve are:

gcc
glibc
libxml and
their corresponding devel packages

In the days where there were no package management tools like yum, pirut, apt-get etc. The old rpms served the installation of these packages with some effort. The task of determining the required rpm package for the required architecture and resolving the other dependencies which arise due to the installation of this rpm may be a tedious task. Some sites which helped in obtaining the necessary rpm suited for our installation and its other dependancies are:

http://rpm.pbone.net/

http://www.rpmfind.net/linux/RPM/

http://ftp.freshrpms.net/

http://dries.ulyssis.org/rpm/packages.html

http://apt.sw.be/

http://rpms.famillecollet.com/ (Remi RPM Repository)

Once everything goes well (we do the ./configure step again to determine this), the make command is executed.

make

If errors are encountered in this stage, We resolve them by installing the unresolved dependencies (Same as the previous step) and then do:

make clean

After this we repeat the make command and then issue:

make install

This process installs the package finally within the system. Modify the init script ( /etc/rc.d/init.d/httpd or /etc/init.d/httpd they are symbolic links) Or sometimes you may even have to create one from the apache site.

The following is the content of one such init script I have used. The line beginning with apachectl/some/path/here and httpd=/some/path/here have to replaced with the appropriate line we have used in the –prefix portion of ./configure.

#!/bin/bash
#
# Startup script for the Apache Web Server
#
# chkconfig: - 85 15
# description: Apache is a World Wide Web server.  It is used to serve \
#              HTML files and CGI.
# processname: httpd
# processname: httpd
# pidfile: /usr/local/apache2/logs/httpd.pid
# config: /usr/local/apache2/conf/httpd.conf
# Source function library.
. /etc/rc.d/init.d/functions
if [ -f /etc/sysconfig/httpd ]; then
. /etc/sysconfig/httpd
fi
# This will prevent initlog from swallowing up a pass-phrase prompt if
# mod_ssl needs a pass-phrase from the user.
INITLOG_ARGS=""
# Path to the apachectl script, server binary, and short-form for messages.
apachectl=/usr/local/webserver/bin/apachectl
httpd=/usr/local/webserver/bin/httpd
pid=$httpd/logs/httpd.pid
prog=httpd
RETVAL=0
# The semantics of these two functions differ from the way apachectl does
# things -- attempting to start while running is a failure, and shutdown
# when not running is also a failure.  So we just do it the way init scripts
# are expected to behave here.
start() {
echo -n $"Starting $prog: "
daemon $httpd $OPTIONS
RETVAL=$?
echo
[ $RETVAL = 0 ] && touch /var/lock/subsys/httpd
return $RETVAL
}
stop() {
echo -n $"Stopping $prog: "
killproc $httpd
RETVAL=$?
echo
[ $RETVAL = 0 ] && rm -f /var/lock/subsys/httpd $pid
}
reload() {
echo -n $"Reloading $prog: "
killproc $httpd -HUP
RETVAL=$?
echo
}
# See how we were called.
case "$1" in
start)
start
;;
stop)
stop
;;
status)
status $httpd
RETVAL=$?
;;
restart)
stop
start
;;
condrestart)
if [ -f $pid ] ; then
stop
start
fi
;;
reload)
reload
;;
graceful|help|configtest|fullstatus)
$apachectl $@
RETVAL=$?
;;
*)
echo $"Usage: $prog {start|stop|restart|condrestart|reload|status"
echo $"|fullstatus|graceful|help|configtest}"
exit 1
esac
exit $RETVAL

Next we add the daemon name to the list of services and run it. For this follow the below steps.

chkconfig --add httpd
chkconfig --level 2345 httpd on
chkconfig --list httpd
/etc/init.d/httpd start
lynx http://localhost/ will display the default apache page which means success.

PHP Compilation
Now we are going to install PHP 5.2.13 from source!
Go to /usr/src/

cd /usr/src/

Download the PHP source tarball and extract it

wget http://in3.php.net/get/php-5.2.13.tar.gz/from/in.php.net/mirror
tar -xzf php*
cd php*

Just like in the previous apache installation, we are going to do the ./configure step with the required setting which are displayed using

./configure --help

We are only interested in enabling php as a module (–with-apxs2) support for mysql (–with-mysql) and prefix line. So we go for:

./configure --with-apxs2=/usr/local/webserver/bin/apxs --with-mysql --prefix=/usr/local/webserver/php

The long command can be written in a shorter, more clearer format with:

./configure --with-apxs2=/usr/local/webserver/bin/apxs \
--with-mysql \
--prefix=/usr/local/webserver/php

The same instructions go for the errors here.
Once everything goes smooth:

make
make install

We can provide the recommeneded php.ini setting in the path /usr/local/webserver/php/lib (what ever is the –prefix + /lib) or just copy the recommended settings to /usr/local/webserver/php/lib (This file may have the name php.ini-recommended or php.ini-production)
cp php.ini-recommended /usr/local/webserver/php/lib/php.ini

From now on we can have php’s index page to be the default index page. For this in the apache’s config file append index.php to the directive – DirectoryIndex

The line would thus look like:

DirectoryIndex index.html index.html.var index.php

To make make apache call modular php to execute the php script when encountered, add the following lines to the conf file.

AddType application/x-httpd-php .php
DirectoryIndex index.html index.html.var index.php

Next to test your installation.
In the default document root, create a phpinfo file with the file name index.php an d the contents as:

<?
phpinfo();
?>

Now we will test the apache configuration for any syntax errors and then reload the apache webserver:

apachectl configtest (No errors should be reported)
/etc/init.d/httpd reload

Open a browser window and load the localhost as URL, we will be viewing the phpinfo page in here. In the phpinfo page, the portion Configure Command shows the actual compilation time options used while ./configure is used. The row corresponding to Server API mentions how the php is loaded. ‘Apache 2.0 Handler’ means that php was loaded as a module of apache. The rest of the values can be globally changed by making the required changes in php.ini or locally in .htaccess (which is possible only because it is loaded as an apache module).

Tips on installing PHP as a CGI

Here we do not require installing apache with the –enable-so option. A normal installation will do. The installation of php will not require the option –with-apxs2. However we will have to mention the location of apache source directory with –with-apache=../apache_1.3.14

In the httpd.conf file you will require adding:

ScriptAlias /php/ [path where your php folder is located]
AddType application/x-httpd-php .php
AddType application/x-httpd-php .php3
AddType application/x-httpd-php .phtml
Action application/x-httpd-php /php/php5

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Enabling mod_rewrite in Apache 2.2

By default CentOS or RHEL flavours of Linux has Apache 2.2 installed. It often becomes a requirement to enable mod_rewrite on these servers. Techs who have been working with cPanel and server with control panels often finds it difficult to troubleshoot issues with a bare server. There are a few things to check or commands to execute in such case where mod_rewrite is shown enabled in the httpd.conf, but not working.

[root@cave html]# httpd -V
Server version: Apache/2.2.3

[root@cave html]# httpd -M
Loaded Modules:
core_module (static)
mpm_prefork_module (static)
http_module (static)
so_module (static)
auth_basic_module (shared)
auth_digest_module (shared)
….
…….
….
rewrite_module (shared)
proxy_module (shared)
proxy_balancer_module (shared)
proxy_ftp_module (shared)
proxy_http_module (shared)
proxy_connect_module (shared)

[root@cave html]# a2enmod rewrite

a2enmod is only to be used if the rewrite_module is not enabled in httpd.conf

Check for the “AllowOverride” settings. It should be set to “All“. By default it will be “None”

Things should work fine after this. Also I found a small good script to check at this URL to see whether mod_rewrite is enabled or not http://www.webune.com/forums/how-to-test-check-if-mod-rewrite-is-enabled-t40.html

Good Luck guys!

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