install and configure VNC Server on CentOS 6.3 or Redhat RHEL

1. Install GNOME Desktop Environnement:

[root@dhcppc1 ~]# yum -y groupinstall “GNOME Desktop Environment”

2. Install KDE Desktop Environnement:

[root@dhcppc1 ~]# yum groupinstall “X Window System” “KDE (K Desktop Environment)”

3. Install VNC Server:

[root@dhcppc1 ~]# yum -y install vnc-server
Loaded plugins: fastestmirror, refresh-packagekit, security
Loading mirror speeds from cached hostfile
* base: mirror-fpt-telecom.fpt.net
* extras: mirror-fpt-telecom.fpt.net
* updates: mirror-fpt-telecom.fpt.net
Setting up Install Process
Resolving Dependencies
–> Running transaction check
—> Package tigervnc-server.i686 0:1.0.90-0.17.20110314svn4359.el6 will be installed
–> Finished Dependency Resolution

Dependencies Resolved

================================================== ==============================
Package Arch Version Repository
Size
================================================== ==============================
Installing:
tigervnc-server i686 1.0.90-0.17.20110314svn4359.el6 base 1.1 M

Transaction Summary
================================================== ==============================
Install 1 Package(s)

Total download size: 1.1 M
Installed size: 2.9 M
Downloading Packages:
tigervnc-server-1.0.90-0.17.20110314svn4359.el6.i686.rpm | 1.1 MB 00:02
warning: rpmts_HdrFromFdno: Header V3 RSA/SHA1 Signature, key ID c105b9de: NOKEY
Retrieving key from file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-6
Importing GPG key 0xC105B9DE:
Userid : CentOS-6 Key (CentOS 6 Official Signing Key) <centos-6-key@centos.org>
Package: centos-release-6-3.el6.centos.9.i686 (@anaconda-CentOS-201207051201.i386/6.3)
From : /etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-6
Running rpm_check_debug
Running Transaction Test
Transaction Test Succeeded
Running Transaction
Installing : tigervnc-server-1.0.90-0.17.20110314svn4359.el6.i686 1/1
Verifying : tigervnc-server-1.0.90-0.17.20110314svn4359.el6.i686 1/1

Installed:
tigervnc-server.i686 0:1.0.90-0.17.20110314svn4359.el6

Complete!
[root@dhcppc1 ~]#

4. Configure a VNC user:

[root@dhcppc1 ~]# su -jackiebui
[jackiebui@dhcppc1 ~]# vncpasswd
Password:******
verify:******
[jackiebui@dhcppc1 ~]# ls .vnc/

5. Edit VNC Configuration File:

[root@dhcppc1 ~]# vi /etc/sysconfig/vncservers
# The VNCSERVERS variable is a list of display:user pairs.
#
# Uncomment the lines below to start a VNC server on display :2
# as my ‘myusername’ (adjust this to your own). You will also
# need to set a VNC password; run ‘man vncpasswd’ to see how
# to do that.
#
# DO NOT RUN THIS SERVICE if your local area network is
# untrusted! For a secure way of using VNC, see this URL:
# http://kbase.redhat.com/faq/docs/DOC-7028

# Use “-nolisten tcp” to prevent X connections to your VNC server via TCP.

# Use “-localhost” to prevent remote VNC clients connecting except when
# doing so through a secure tunnel. See the “-via” option in the
# `man vncviewer’ manual page.

VNCSERVERS=”1:jackiebui” //Uncomment 2 last lines, and edit your VNC user
VNCSERVERARGS[2]=”-geometry 800×600 -nolisten tcp -localhost” // Save and exit

6. Start VNC Server:

[root@dhcppc1 ~]# vncserver
[root@dhcppc1 ~]# chkconfig vncserver on //VNC’ll start at boot

Note: If you have error 

Fatal server error:
could not open default font 'fixed'

Than 

yum -y install libXfont

7. Now use VNC viewer to connect to VNC Server:

8. Type your VNC password:

9. Now you can access your VNC Server from everywhere:

That's all. If you have any problems,just comment here,i'll reply ASAP! 

Enable Remote Access To MySQL Database Server

How Do I Enable Remote Access To MySQL Database Server?

By default remote access to the MySQL database server is disabled for security reasons. However, some time you need to provide remote access to database server from home or a web server. This post will explain how to setup a user account and access mysql server remotely.

Task: MySQL Server Remote Access

You need type the following commands which will allow remote connections.

Step # 1: Login Using SSH (if server is outside your data center)

First, login over ssh to remote MySQL database server. You may need to login to your MySQL server as the root user:

ssh user@server1.cyberciti.biz
### login as the root using su or sudo ##
su
#sudo -s
 

OR directly login as root user:

ssh root@server1.cyberciti.biz

Step # 2: Edit the my.cnf file

Once connected you need to edit the MySQL server configuration file my.cnf using a text editor such as vi:

• If you are using Debian Linux file is located at /etc/mysql/my.cnf location.
• If you are using Red Hat Linux/Fedora/Centos Linux file is located at /etc/my.cnf location.
• If you are using FreeBSD you need to create a file /var/db/mysql/my.cnf location.

Edit the /etc/my.cnf, run:
# vi /etc/my.cnf

Step # 3: Once file opened, locate line that read as follows

[mysqld] 

Make sure line skip-networking is commented (or remove line) and add following line

bind-address=YOUR-SERVER-IP

For example, if your MySQL server IP is 65.55.55.2 then entire block should be look like as follows:

[mysqld]
user            = mysql
pid-file        = /var/run/mysqld/mysqld.pid
socket          = /var/run/mysqld/mysqld.sock
port            = 3306
basedir         = /usr
datadir         = /var/lib/mysql
tmpdir          = /tmp
language        = /usr/share/mysql/English
bind-address    = 65.55.55.2
# skip-networking
....
..
....

Where,

• bind-address: IP address to bind to.
• skip-networking : Don’t listen for TCP/IP connections at all. All interaction with mysqld must be made via Unix sockets. This option is highly recommended for systems where only local requests are allowed. Since you need to allow remote connection this line should be removed from my.cnf or put it in comment state.

Step# 4 Save and Close the file

If you are using Debian / Ubuntu Linux, type the following command to restart the mysql server:
# /etc/init.d/mysql restart
If you are using RHEL / CentOS / Fedora / Scientific Linux, type the following command to restart the mysql server:
# /etc/init.d/mysqld restart
If you are using FreeBSD, type the following command to restart the mysql server:
# /usr/local/etc/rc.d/mysql-server stop
# /usr/local/etc/rc.d/mysql-server start
OR
# /usr/local/etc/rc.d/mysql-server restart

Step # 5 Grant access to remote IP address

Connect to mysql server:
$ mysql -u root -p mysql

Grant access to a new database

If you want to add a new database called foo for user bar and remote IP 202.54.10.20 then you need to type the following commands at mysql> prompt:mysql> CREATE DATABASE foo;
mysql> GRANT ALL ON foo.* TO bar@'202.54.10.20' IDENTIFIED BY 'PASSWORD';

How Do I Grant Access To An Existing Database?

Let us assume that you are always making connection from remote IP called 202.54.10.20 for database called webdb for user webadmin, To grant access to this IP address type the following command At mysql> prompt for existing database, enter:
mysql> update db set Host='202.54.10.20' where Db='webdb';
mysql> update user set Host='202.54.10.20' where user='webadmin';

Step # 6: Logout of MySQL

Type exit command to logout mysql:mysql> exit

Step # 7: Open port 3306

You need to open TCP port 3306 using iptables or BSD pf firewall.

A sample iptables rule to open Linux iptables firewall

/sbin/iptables -A INPUT -i eth0 -p tcp --destination-port 3306 -j ACCEPT

OR only allow remote connection from your web server located at 10.5.1.3:

/sbin/iptables -A INPUT -i eth0 -s 10.5.1.3 -p tcp --destination-port 3306 -j ACCEPT

OR only allow remote connection from your lan subnet 192.168.1.0/24:

/sbin/iptables -A INPUT -i eth0 -s 192.168.1.0/24 -p tcp --destination-port 3306 -j ACCEPT

Finally save all rules (RHEL / CentOS specific command):
# service iptables save

A sample FreeBSD / OpenBSD pf rule ( /etc/pf.conf)

pass in on $ext_if proto tcp from any to any port 3306

OR allow only access from your web server located at 10.5.1.3:

pass in on $ext_if proto tcp from 10.5.1.3 to any port 3306  flags S/SA synproxy state

Step # 8: Test it

From your remote system or your desktop type the following command:
$ mysql -u webadmin –h 65.55.55.2 –p
Where,

• -u webadmin: webadmin is MySQL username
• -h IP or hostname: 65.55.55.2 is MySQL server IP address or hostname (FQDN)
• -p : Prompt for password

You can also use the telnet or nc command to connect to port 3306 for testing purpose:
$ echo X | telnet -e X 65.55.55.2 3306
OR
$ nc -z -w1 65.55.55.2 3306
Sample outputs:

Connection to 65.55.55.2 3306 port [tcp/mysql] succeeded!

How to restore default system permissions on Red Hat, CentOs, Fedora

I recently came across a system which had some directories set to 777(recursively), the sysadmin needed to install an application and changed all the permissions!!!! a mess, I didn't know where to start, but one of my colleagues pointed that rpm has a parameter called --setperms and --setugids.

I created a one liner that does the job, it takes time but It works !!!!!

1) To reset uids and gids on files and directories :


for u in $(rpm -qa); do rpm --setugids $u; done

2) To permissions on files and directories

for p in $(rpm -qa); do rpm --setperms $p; done


Enjoy,