Linux : VNC - Virtual Network Computing

Objective: To create VNC server and make this accessible for the remote client.

Description:

Virtual Network Computing (VNC) is a graphical desktop sharing system.

VNC is platform-independent -a VNC viewer on one operating system may connect to a VNC server on the same or any other operating system.

Environment: Redhat Linux 5.0 32-bit.

1. VNC server

Hostname: server

IP address:192.168.56.99

2. Remote user

IP address:192.168.56.102

Hostname:appserver

Plan:

- Install and verify "vnc" packages.

- Create your VNC users.

- Set your users' VNC passwords.

- Edit the server configuration.

- Create and customize xstartup scripts.

- Start the VNC service.

- Test VNC user.

1. Verify install both the packges of VNC server.

[root@server ~]# rpm -qa vnc*

Install VNC server and client package.

[root@server ~]# yum install -y vnc*

[root@server ~]# yum list vnc*

Installed Packages

vnc.i386                                 4.1.2-9.el5            installed

vnc-server.i386                       4.1.2-9.el5            installed

2. Create VNC user.

[root@server ~]# useradd sunlnx

[root@server ~]# passwd sunlnx

3. Edit VNC server configurations.

Append the below lines in config file(/etc/sysconfig/vncservers)

VNCSERVERS="1:sunlnx"

VNCSERVERARGS[1]="-geometry 640x480"

[root@server ~]# tail -2 /etc/sysconfig/vncservers

VNCSERVERS="1:sunlnx"

VNCSERVERARGS[1]="-geometry 640x480"

4. Need to create default startup scripts.

[root@server ~]# vncserver

You will require a password to access your desktops.

Password:

Verify:

New 'server:1 (root)' desktop is server:1

Creating default startup script /root/.vnc/xstartup

Starting applications specified in /root/.vnc/xstartup

Log file is /root/.vnc/server:1.log

This would have created .vnc directory in $HOME.

[root@server ~]# ls -ld .vnc/

drwxr-xr-x 2 root root 4096 Jul 14 13:40 .vnc/

[root@server ~]# ls .vnc/

passwd  server:1.log  server:1.pid  xstartup

5. Create xstartup scripts.

We will create the xstartup scripts by starting and stopping the vncserver as root.

[root@server ~]# service vncserver start

Starting VNC server: 1:sunlnx

New 'server:1 (sunlnx)' desktop is server:1

Starting applications specified in /home/sunlnx/.vnc/xstartup

Log file is /home/sunlnx/.vnc/server:1.log

                                                           [  OK  ]

[root@server ~]# service vncserver stop

Shutting down VNC server: 1:sunlnx                         [  OK  ]

[root@server ~]#

6. VNC server listens on port 5901.

[root@server ~]# netstat -nalt

tcp        0      0 0.0.0.0:5901                0.0.0.0:*                   LISTEN

7. Install "vncviewer" on the remoted system, and connect to the VNC server.

Below are the snaps.

Objective successful.

Linux talk - talk to another user

I came across talking to same users(/etc/passwd)in the local server. The same could be used to even talk to the users remotely.

To talk to the user who is logged in more than once, use ttyname to indicate the appropriate terminal name.Once communication has been established, the two parties may type simultaneously.

Let's see how can we configuire this.

1. Verify the package is installed, if not install by 'yum' or 'rpm'.

[root@server ~]# rpm -qa | grep talk

talk-0.17-29.2.2

talk-server-0.17-29.2.2

[root@server ~]#

2. Change Disable=no in talk file.

[root@server ~]# vi /etc/xinetd.d/talk

# default: off

# description: The talk server accepts talk requests for chatting with users \

#       on other systems.

service talk

{

        flags                   = IPv4

        disable                 = no

        socket_type             = dgram

        wait                    = yes

        user                    = nobody

        group                   = tty

        server                  = /usr/sbin/in.talkd

}

3. Make sure both 'talk' and 'ntalk' are 'on'

[root@server ~]# chkconfig --list | grep talk

        ntalk:          on

        talk:            on

4. Restart 'xinetd' service to take effect.

[root@server ~]# service xinetd restart

Stopping xinetd:                                           [  OK  ]

Starting xinetd:                                            [  OK  ]

Case 1:

I shall communicate to different user(login names)on the same server. 

[root@server ~]# grep "^root" /etc/passwd

root:x:0:0:root:/root:/bin/bash

[root@server ~]# grep "sysadm" /etc/passwd

sysadm:x:854:855::/home/sysadm:/bin/bash

Case 2:

Talk to a user who is logged in more than once.Here, you need to communicate with their terminal name.

[root@server ~]# tty

/dev/pts/1

[sysadm@server ~]$ tty

/dev/pts/3

Enjoy CLI in your work environment.