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Attackers after getting access to a server, will install a rootkit to hide their identity and run desired scripts anywhere within the server. It makes the life of a hacker easy once installed. Rootkits are not easily detectable. Sometimes, if the rootkit is one of the latest ones without a diagnosis, the server will have to be rebuild from scratch.

A rootkit will have multiple applications for cracking the entire server, some of them are:

Server Access Applications (Back door application)
These applications will create a backdoor to log in to the hacked system without using the exploit again.

Log clearing Applications
These applications clear the logs of the events performed by the hacker or the applications used. They all the associated log files in the server.

Packet sniffing Applications
These applications monitor the data through the various interfaces in the server at particular ports.

Malicious Scripts
Many scripts will be installed like IRC bots, ddos daemons, spam servers, trojans, worms etc.

There are mainly two kinds of root kits. The application rootkit and the kernel rootkit.

Application rootkits
These rootkits mimic a particular application and will hide the attackers files/processes from being revealed by the original application. To illustrate, a rootkit ls application will perform all the task of a normal ls but will not display any of the files of the attacker. Other application rootkits will create backdoors for unauthorised access, packet sniffers etc which go undetected or are hidden by renaming. Application rootkits are the most common.

Kernel rootkits
Kernel rootkits modify the kernel and apply patches to the kernel and device drivers. They also hide the applications and files of the attacker. As antivirus and other applications run beneath the kernel, they are the most undetectable rootkits.

‘Prevention is better than cure’ – as this saying goes, it is always better to keep the system secure and updated when ever possible to stop these installations. There are some applications which help detect any known rootkits running in the system. One such is the chkrootkit.

chkrootkit is one of the popular rootkit detectors (an anti-rootkit) and it is know to detect common rootkits on unix/linux servers. chkrootkit relies on basic string processing techniques to determine the presence of rootkits. It scans specific sytem files and binaries targeted by rootkits for known signatures.

The following are the instructions to install chkrootkit version 0.49 in a server.

cd /usr/local/

wget ftp://ftp.pangeia.com.br/pub/seg/pac/chkrootkit.tar.gz

wget ftp://ftp.pangeia.com.br/pub/seg/pac/chkrootkit.md5

md5sum -c chkrootkit.md5 # to check if the downloaded file is intact

tar -xzf chkrootkit.tar.gz

cd chkrootkit-0.49/

make sense

./chkrootkit

chkroootkit will check all the files and display the status of the files analysed. This information may be logged for future reference. For this a cron job may be setup to be run at least once a month.

Inserting an entry like the one below into the systems cron tasks (executed atleast once a month) will send the report of the chkrootkit vulnerabilities to the administrator conserned.

/usr/local/chkrootkit-0.49/chkrootkit | mail -s "chkrootkit report $(date +%d/%m/%y)" "admin@domain.com"

Postgres is one of the best open-source database alternative which is fully object oriented and transactions compliant. It has stored procedures, multiple views and a huge set of datatypes. Some of the other notable features are as follows.

Objects and Inheritance

Database consists of objects and the database administrators can design custom or user-defined objects for the tables. Inheritance is another feature. Tables can be set to inherit their characteristics from a “parent” table.

Functions

Functions can be used in Postgres. These can be written in the postgres’ own procedural language called ‘PL/pgSQL’ which resembles Oracle’s procedural language ‘PL/SQL’ or any other common scripting languages which support posgtres’ procedural language like PL/Perl, plPHP, PL/Python, PL/Ruby etc. Run the following in the psql client to determine if functions is enabled:

SELECT true FROM pg_catalog.pg_language WHERE lanname = 'plpgsql'; 

To create user-defined functions we use the CREATE OR REPLACE FUNCTION command. Example:

CREATE OR REPLACE FUNCTION fib (

fib_for integer

) RETURNS integer AS $$

BEGIN

IF fib_for < 2 THEN

RETURN fib_for;

END IF;

RETURN fib(fib_for - 2) + fib(fib_for - 1);

END;

$$ LANGUAGE plpgsql;

Indexes

An index is like a summary of a certain portion of the table. It is an optimization technique which increases speed of accessing records from a database. PostgreSQL supports indexes like Btree, hash etc. User-defined index methods can also be created. Indexes are created on tables with respect to a particular field (based on which there are a number of queries). As an example for a table:

CREATE TABLE name (

id integer,

fname varchar

lname varchar

);

To create an index on table name with respective to the field id (as there are many queries on this table requesting for firstname or lastname from the id provided), we use the index:

CREATE INDEX name_id_index ON name (id);

Triggers

Triggers are events or functions run upon the action of certain SQL statements which modify data in some records. Depending on the kind of modification we can have multiple triggers in a database. Postgres supports multiple triggers written in PL/PgSQL or it’s scripting counterparts like PL/Python. The trigger function must be defined before the trigger can be created. The trigger function must be declared as a function taking no arguments and returning type trigger. CREATE TRIGGER command is used to declare triggers.

Concurrency

PostgreSQL ensures concurrency with the help of MVCC (Multi-Version Concurrency Control), which gives the database user a “snapshot” of the database, allowing changes to be made without being visible to other users until a transaction is committed.

PostgreSQL’s MVCC keeps all of the versions of the data together in the same partition in the same table. By identifying which rows were added by which transactions, which rows were deleted by which transactions, and which transactions have actually committed, it becomes a straightforward check to see which rows are visible for which transactions.

Inorder to accomplish this, Rows of a table are stored in PostgreSQL as a tuple. Two fields of each tuple are xmin and xmax. Xmin is the transaction ID of the transaction that created the tuple. Xmax is the transaction ID of the transaction that deleted it (if any).

Along with the tuples in each table, a record of each transaction and its current state (in progress, committed, aborted) is kept in a universal transaction log.

When data in a table is selected, only those rows that are created and not destroyed are seen. That is, each row’s xmin is observed. If the xmin is a transaction that is in progress or aborted, then the row is invisible. If the xmin is a transaction that has committed, then the xmax is observed. If the xmax is a transaction that is in progress or aborted and not the current transaction, or if there is no xmax at all, then the row is seen. Otherwise, the row is considered as already deleted.

Insertions are straightforward. The transaction that inserts the tuple simply creates it with the xmax blank and the xmin set to its transaction ID. Deletions are also straightforward. The tuple’s xmax is set to the current transaction. Updates are no more than a concurrent insert and delete.

Views

A view is a table which does not exist in the database. It is a virtual table created from fields in various tables and is joined together based on some criteria. Views can be used in place of tables and will accomplish the task same as that of a table. The CREATE VIEW statement is used to accomplish this eg:

CREATE VIEW best_sellers AS

SELECT * FROM publishers WHERE demand LIKE 'high';

Foreign Keys

The primary key used in one table which is used to refer to the records in a second table is called the foreign key of the second table.

CREATE TABLE products (
    product_no integer PRIMARY KEY,
    name text,
    price numeric
);
CREATE TABLE orders (
    order_id integer PRIMARY KEY,
    product_no integer REFERENCES products (product_no),
    quantity integer
);

Here product_no is the foreign key in the second table created. The foreign key field may have values which are repeated unlike primary keys.

Files Users and Configuration

The main configuration file of Postgres is postgresql.conf. This can be located in the ‘data’ directory. It may be present either in /var/lib (/var/lib/pgsql/data/postgresql.conf) or /usr/local (/usr/local/pgsql/data/postgresql.conf). Temporary changes to the configurations can be made using postmaster command.

The init script that starts the postgres service is /etc/init.d/postgresql . It runs a number of child processes concurrently. The postgres server process is postmaster. These processes and files associated with PosgreSQL are owned by the user/group postgres. The default port used for database connections is 5432

The user postgres is the PostgreSQL database superuser. We can create a number of super users for the database (this accomplished by the create role command ), however, the default super user is postgres. The postgres user has the privilege to access all the databases and files in the server (Unless the user root is created in postgres as a superuser).

Client Authentication is controlled by the file pg_hba.conf in the data directory, e.g., /var/lib/pgsql/data/pg_hba.conf. (HBA stands for host-based authentication.)

Each record specifies a connection type, a client IP address range (if relevant for the connection type), a database name or names, and the authentication method to be used for connections matching these parameters.A record is typically in one of two forms:

local database authentication-method [ authentication-option ]

host database IP-address IP-mask authentication-method [ authentication-option ]

local : This record pertains to connection attempts over Unix domain sockets.

host : This record pertains to connection attempts over TCP/IP networks.

database : Specifies the database that this record applies to. The value all specifies that it applies to all databases, while the value sameuser identifies the database with the same name as the connecting user.

authentication methods

trust: The connection is allowed unconditionally.

reject: The connection is rejected unconditionally.

password: The client is required to supply a password which is required to match the database password that was set up for the user.

md5: Like the password method, but the password is sent over the wire encrypted using a simple challenge-response protocol.

ident: This method uses the “Identification Protocol” as described in RFC 1413. It may be used to authenticate TCP/IP or Unix domain socket connections, but its reccomended use is for local connections only and not remote connections.

Front-ends

The minimalistic front-end for PostgreSQL is the psql command-line. It can be used to enter SQL queries directly, or execute them from a file. phpPgAdmin is a web-portal used for PostgreSQL administration written in PHP and based on the popular phpMyAdmin. Likewise pgAdmin is a graphical front-end administration tool for PostgreSQL, which has support on multiple platforms. The latest stable version of the same is pgAdmin III.

Some administration related commands

Command to login to psql database mydb as user myuser:

psql -d mydb -U myuser

Command to login to psql database mydb as user myuser on a different host myhost:

psql -h myhost -d mydb -U myuser

If the port the server runs is different we use -p [port number] . Upon entering the psql shell the prompt will show the database name currently being used. In the above example it will show

mydb=> (if logged in as an ordinary user )

mydb=# (if logged in as a super user like postgres)

Create a PostgreSQL user

There are two ways to create a postgres database user. The only user initially allowed to create users is postgres. So one has to switch to this user before creating other users with varying privileges.

1. Creating the user in the shell prompt, with createuser command.

switch to the postgres user with:

su - postgres

createuser tom

Shall the new role be a superuser? (y/n) n

Shall the new role be allowed to create databases? (y/n) y

Shall the new role be allowed to create more new roles? (y/n) n

2. Creating the user in the PSQL prompt, with CREATE USER command.

switch to the postgres user with:

su - postgres

create user mary with password 'marypass';

Creating and deleting a PostgreSQL Database

There are two way to create databases.

1. Creating database in the PSQL prompt, with createuser command.

CREATE DATABASE db1 WITH OWNER tom;

2. Creating database in the shell prompt, with createdb command.

createdb db2 -O mary

To delete an entire database from within the psql prompt do :

DROP DATABASE db1;

Determining execution time of a query

Turn on timing with

\timing

Now execute the qery:

SELECT * from db1.employees ;

Time: 0.065 ms

Calculate postgreSQL database size in disk

SELECT pg_database_size('db1');

to get the values in human readable format

SELECT pg_size_pretty(pg_database_size('db1'));

to calculate postgreSQL table size in disk

SELECT pg_size_pretty(pg_total_relation_size(‘big_table’));

Slash commands used in psql

To list all slash commands and thier purpose. Login to psql and issue to the command \? . Some of the most commonly used slash commands are the following:

The below can be used with a specific table/index/view name for description of the specific table/index/view

Useful Bash commands

Bash command to list all the postgresql databases:

psql -l #This can be run as a unix user who is also a super user in postgresql

Indirect bash command to list all the postgresl users:

psql -c '\du' #-c is used to run an internal or sql command in psql shell

Backing up and restoring databases

To dump the database to an sql file use the bash command:

pg_dump mydb > db.out

To restore a database from an sql backup file (via bash)

psql -d newdb -f backupdb.out

or

psql -f backupdb.out newdb

(here the database newdb must be already created and the file backupdb.out must be present in the current directory)

To take the backup of all the Postgres databases in the server:

pg_dumpall > /var/lib/pgsql/backups/dumpall.sql

(Only possible with the postgres or the database superuser )

Resetting database user’s password

To change the password for a database user (say ‘thomas’):

ALTER USER thomas WITH PASSWORD 'newpassword';

This same command can be used to reset the password for the postgresql super user postgres, but in this case, you will have to enable password less login for postgres user by adding the following line to the top of the file pg_hba.conf in the data directory of postgres. Once the password is reset this line can be removed:

local	all	postgres	trust

Next we issue the same command but for the user postgres

ALTER USER postgres WITH PASSWORD 'newpassword';

To create a super user via bash with multiple roles

createuser -sPE mysuperuser

Instead of this we can also use the below psql shell command:

CREATE ROLE mysuperuser2 WITH SUPERUSER CREATEDB CREATEROLE LOGIN ENCRYPTED PASSWORD 'mysuperpass2';

Physical database files in postgres

The files in data/base are named by the oid (Object Identifier) of the database record in

pg_database, like this:

cd /var/lib/pgsql/data/base

ls -l

total 33

drwx------ 22 postgres postgres 4096 Jul 23 20:06 ./

drwx------ 11 postgres postgres 4096 Aug  1 05:59 ../

drwx------  2 postgres postgres 4096 Jun 20 09:32 1/

drwx------  2 postgres postgres 4096 Mar  3 13:36 10792/

drwx------  2 postgres postgres 4096 Jun 20 15:09 10793/

drwx------  2 postgres postgres 4096 May 27 01:40 16497/

drwx------  2 postgres postgres 4096 May 27 01:40 16589/

drwx------  2 postgres postgres 4096 Jun 20 10:28 16702/

drwx------  2 postgres postgres 4096 May 27 01:40 16764/

drwx------  2 postgres postgres 4096 May 27 01:40 16785/

drwx------  2 postgres postgres 4096 Aug  1 04:37 16786/

drwx------  2 postgres postgres 4096 Aug  1 04:36 19992/

drwx------  2 postgres postgres 4096 May 27 01:40 19997/

To obtain the oid, execute the following command in psql prompt

postgres=# select oid,datname from pg_database order by oid;

   oid  |         datname

---------+--------------------------

1 | template1

10792 | template0

10793 | postgres

16497 | gadgetwi_Unable

16589 | vimusicc_filehost

16702 | personea_altissimo

16764 | shopping_businessfinance

16785 | ansonyi_wp2

16786 | ansonyi_wp

19992 | globook_PostgreSQL

In the protocol stack used in the internet. The SSL protocol runs above TCP/IP and below higher-level protocols such as HTTP or IMAP.

The SSL protocol includes two sub-protocols:
1) SSL record protocol
2) SSL handshake protocol

The SSL record protocol defines the format used to transmit data. The SSL handshake protocol involves using the SSL record protocol to exchange a series of messages between an SSL-enabled server and an SSL-enabled client when they first establish an SSL connection.

Now SSL for the layman
SSL basically creates an encrypted communication channel between the two parties involved in the communication. For a third person involved in the middle of this communication channel, the data seems to be garbled.

Suppose Alice (A, the browser) wishes to communicate with Bob (B, the server) then the exact steps that takes place inorder to begin the encrypted communication are:

1) A -> B hello
Alice contacts Bob and requests for a private communication (request for an https link at port 443)

2) B -> A Hi, I’m Bob, bobs-certificate
Bob send back to Alice his certificate. A certificate authenticates that it is Bob who is actually communicating with Alice. It is like a unique ID card displayed.

3) A -> B prove it
Alice requests Bob to prove his identity.

4) B -> A Alice, This Is bob { digest[Alice, This Is Bob] } bobs-private-key
Bob sends back a message and its digest encrypted with his private key. This step can also be like sending a document with a digital signature (when you have Alice’s public key).

5) A -> B ok bob, here is a secret {secret} bobs-public-key
Alice sends back to Bob some secret. Usually a session key encrypted using Bob’s public key obtained from his certificate

6) B -> A {some message,MAC}secret-key
Next Bob generates a secret key from Alice’s secret (earlier step) and sends back to Alice the real message and its MAC encrypted with this secret key. This is actually the encrypted website.

Terminologies

Certificate
This is actually bobs public key containing document which is digitally signed by a certificate issuer’s private key (like Verisign). In this process Verisign gets all the necessary documents to verify that Bob’s identity is correct and it gets Bob’s public key (and some other data like certificate expiry period, Bobs identity) and encrypts it with its own private key. Now Verisign’s public key comes built-in along with every browser (so that the browser can get bobs public key from within it).

Digest
Digest or more appropriately Message Digest is like a summary of the actual message or a portion of the message. The digest of a message is is unique for every unique message, it is a one way function such that obtaining the digest, it is never possible to recover the original message (This does not involve using any key in the process). Message Digest always appears with the original message. Upon reception of this Message and its digest at the receiver’s end, the receiver can once again calculate the digest from the original message and verify the integrity of the message.

Digital signature
Let Bob send a document to Alice which is digitally signed. For this Bob must have Alice’s public key and Alice must have Bob’s public key.Bob takes the document, encrypts it first with Alice’s public key and next with its own private key(Bob’s)

B -> A [{message}alices-public-key ]bobs-public-key

Session Key
The only secret which is communicated using public key encryption is a session key. Now the session key is chosen from the ‘secret’ that the parties accept. the session key could be the secret itself or a portion of the secret or the result when the secret is passed through a previously agreed algorithm. The SSL encrypted communication does’t necessary have to be created using a public key encryption technique (This uses a lot of overhead, i.e. processing and time), it may be simple symmetric cypher(less overhead) using this session key once agreed upon. There are a variety of cypher suites available (IDEA Blow-fish RSA DES MD5 KEA) and both the parties may choose some encryption technique based on the protocol used (SSL1.0 SSL2.0 TLS etc)

MAC
MAC or Message Authentication Code is similar to the Message Digest we have discussed. It is used to verify the integrity of the Message.

MAC := Digest[ some message, secret ]

Files associated with SSL

CSR
CSR or Certificate Signing Request is a string of text generated by the server. This file is sent to the SSL vendor while purchasing an SSL. In the process of generating your CSR, you provide a number of details regarding the domain being registered. Excerpts of text from all these are taken to generate your private key. This private key is present only within the server and nowhere else. The content of the CSR basically contains the public key along with all the details you have used. You get this as domain.com.csr or domain_com.csr.

CA bundle
CA (Certificate Authority) bundle file is one which contains the public key of the Certificate Issuer (Like Verisign’s public key). Usually this is not required while installing the SSL and most browsers will have this detail in advance to decrypt the SSL certificate (the CRT file) from the server. You get this as domain.com.cabundle or domain_com.ca-bundle.

CRT
This is the actuall SSL certificate as obtained from the SSL vendor. It is a file (containing the public key of the domain secured with SSL and other details like the expiry date, owner information, address etc of the SSL) which is encrypted with the private key of the SSL vendor (Digitaly signed by the SSL vendor). You get this as domain.com.crt or domain_com.crt .

Key file
This is the file which holds your private key (strictly confidential material). The file will have the RSA private key as generated by your server software. You get this as customcardsplus.com.key or customcardsplus_com.key. This file is not usually send to your SSL vendor unlike the CSR. You get this as domain.com.key or domain_com.key .

SSL in a cPanel server
Any service can be secured in a communication channel which is encrypted with SSL. Each of this service on the encrypted channel will be on a different port. Some of them are as follows:

A domain served as a secure webpage will require a dedicated IP (in a shared environment). SSL protocol is designed to use IP-based mapping. SSL does not support host headers. Therefore, you should have a unique IP address assigned to your secure site. These pages are served from the port 443. Let us examine the configuration of such a website in the apache’s config file /usr/local/apache/conf/httpd.conf.

Every website (in our example domain.com with username: doma) enabled with SSL has a unique set of directives in the VirtualHost section for the 443 port as:

<VirtualHost 266.11.208.293:443\> Dedicated IP of the domain

ServerName domain.com #Domain name secured with SSL
ServerAlias www.domain.com

DocumentRoot /home/doma/public_html

ServerAdmin webmaster@domain.com
UseCanonicalName off
CustomLog /usr/local/apache/domlogs/domain.com combined

CustomLog /usr/local/apache/domlogs/domain.com-bytes_log "%{%s}t %I .\n%{%s}t %O ."
ScriptAlias /cgi-bin/ /home/doma/public_html/cgi-bin/
SSLEngine on #This directive enables the SSL on this domain
SSLCertificateFile /etc/ssl/certs/www.domain.com.crt #Location of CRT file
SSLCertificateKeyFile /etc/ssl/private/www.doma.com.key #Location of Private key
SSLCACertificateFile /etc/ssl/certs/www.domain.com.cabundle #Location of CAbundle file
CustomLog /usr/local/apache/domlogs/domain.com-ssl_log combined #Log specific for the SSL served webpage
SetEnvIf User-Agent ".*MSIE.*" nokeepalive ssl-unclean-shutdown

<Directory "/home/doma/public_html/cgi-bin">
SSLOptions +StdEnvVars #This directive will pass mod_ssl environment variables to the server scripts.
</Directory>

</VirtualHost>

Some times the directive SSLCertificateChainFile is used in place of SSLCACertificateFile. The minimal addition you will have to make to enable SSL in your httpd.conf file is:

<VirtualHost 192.168.0.1:443>
DocumentRoot /var/www/html
ServerName www.yourdomain.com
SSLEngine on
SSLCertificateFile /path/to/your_domain_name.crt
SSLCertificateKeyFile /path/to/your_private.key
SSLCertificateChainFile /path/to/DigiCertCA.crt
</VirtualHost>

There are two locations where you are likely to find the SSL related files in your cPanel server. Usually the crt, key and the ca bundle are present in the home directory of the user in /home/username/ssl/, if it was installed using the client’s cpanel. However if the WHM was used instead to install the same, you will find it in /etc/ssl/. In either of these locations you will find two directories: certs/ and private/. certs contain the crt and cabundle while the private contains the keys.

Now you know how ssl works in your server, Any more questions? just comment!

How to solve this

Pre-Requisites : You should have Shell access (as root) to the Node server.

Mostly this happens due to inode issue. The inodes allocated to the server maybe full. inode is a data structure on a traditional Unix-style file system such as UFS. An inode stores basic information about a regular file, directory, or other file system object.

Steps

Say we are logged into the Node Server. There we are going to list all the Containers existing on the Hardware Node. By default, only running Containers are shown.

[root@linuxvps1 ~]# vzlist -a
CTID    NPROC STATUS   IP_ADDR        HOSTNAME
100     18  running    100.20.11.111  WEB.EXAMPLE.COM
101     63  running    100.20.12.203  -
102     169 running    100.20.92.182  server2.example.com
103     81  running    100.20.56.169  example.net
78965   236 running    100.20.77.204  server1.example.com

Assume your container is 103. So simply enter into 103 by this command

[root@linuxvps1 ~]# vzctl enter 103

Check if the inodes are full in the container

[root@linuxvps1 ~]# df -i

Most Probably it should display something like this :

Filesystem      Inodes      IUsed        IFree     IUse%      Mounted on
/dev/vzfs       200000      200000       0         100%       /
none            65536       95           65441     1%         /dev

Bang ! The inodes on /dev/vzfs mounted on / are full. You’ve to go nowhere else to see why that error was delivered. A simple solution will work out, you’ve to increase the inode limit. You’ve two options, either through Shell or through the Node Control Panel (like Parallels Infrastructure Manager)

First we will go through Shell mode with this command :

$ vzctl set veid --diskinodes softlimit:hardlimit 

Where ‘veid’ is the VPS ID

root@linuxvps1 ~]# vzctl set 103 --diskinodes 7680100:7680200

Second we are going for Node Control Panel. In the infrastructure, you will see your VPS with a ! sign. That indicates your VPS is having some sort of issue.

So you’ve seen the Alert. Next access the VPS, go to Resources tab. I’m sorry to tell you that I grabbed this screenshot after resolving the issue, but it will help you anyway

You should see the ‘Disk Inodes’ is full under ‘Disk Usage’ category (Here it is not !). Next Click Configure to settle this one

See the Highlighted part, the inodes should be limited to some size. Increase it or remove the check mark to make it unlimited.  Make sure you save the changes. Now try again accessing cpanel/WHM/Webmail. It should load with out any issues.That makes a smile in your face, isn’t it ?

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

Usually, we need to add or remove an IP address in the VPS. Here we go :

Prerequisites

You need Node Server access for these (then only you can manage those VPS), that too SSH root access. The VPS should be either OpenVZ or Virtuozzo.

Steps

Say we are logged into the Node Server. There we are going to list all the Containers existing on the Hardware Node. By default, only running Containers are shown.

[root@linuxvps1 ~]# vzlist -a
CTID    NPROC STATUS   IP_ADDR        HOSTNAME
100     18  running    100.20.11.111  WEB.EXAMPLE.COM
101     63  running    100.20.12.203  -
102     169 running    100.20.92.182  server2.example.com
103     81  running    100.20.56.169  test.example.net
78965   236 running    100.20.77.204  server1.example.com

Lets consider the VPS with ID 78965 needs the new IP 100.20.80.200 to be added. So the command will be :

[root@linuxvps1 ~]# vzctl set 78965 --ipadd 100.20.80.200
Adding IP address(es): 100.20.80.200 WARNING: Settings were not saved. On next start the original values will be applied.
Use --save to save the settings in the configuration file.

Save the Settings (this command will do the purpose instead of the above one)

[root@linuxvps1 ~]# vzctl set 78965 --save --ipadd 100.20.80.200
Adding IP address(es): 100.20.80.200 Saved parameters for Container 78965.

Thats it, now login to WHM and access ‘Change Site’s IP Address’. Select the website and change the IP address from the drop down list.

To remove an IP from the VPS

[root@linuxvps1 ~]# vzctl set 78965 --save --ipdel 100.20.80.200
Deleting IP address(es): 100.20.80.200 Saved parameters for Container 78965.

Mission Accomplished !

Just follow the KB at http://wiki.openvz.org/VPN_via_the_TUN/TAP_device

Error Note: Cannot set tx queue length on tun0: Operation not permitted (errno=1)

As mentioned in the same KB URL, just do the steps below and things should be alright again

vzctl set 101 --devices c:10:200:rw --save
vzctl set 101 --capability net_admin:on --save

Basically the errors are caused by the non-execution of the two commands mentioned above.