Cento 5: To Configure the DNS server

tjie
tjie used Ask the Experts™
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Hi,

1) I have a linux server (which host name is Centos_5) in the Active Directory Environment
2) The Domain Controllers (DC1 and DC2) and the Centos_5 are in LAN 1
- LAN 1: 172.17.17.0/24
- The IP of Centos_5 is "172.17.17.30"
- DC1 is "172.17.17.10"
- DC1 and Centos_5 can ping each other by its IP addresses

3) My Goal:
- I want to configure the DNS server for Centos_5 (the DNS server or name server are the IP of DC1 and DC2 (172.17.17.10 and 172.17.17.11)

4) At Centos_5
- Login as root
- cd /etc
- [root@Centols_5 etc]#
- Type in: gedit resolv.conf
- The error messages:

xlib: connection to ":0.0" refused by server
xlib: no protocol specified

cannot open display:
Run 'gedit --help' to see a full list of available command line options

5) As I mention above that the goal is to configure the DNS server or name servers at Centos_5
6) Any help?
7) Thanks

tjie
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Top Expert 2011
Commented:
as root
1. backup /etc/resolve.conf
cp /etc/resolve.conf /etc/resolv.conf_backup

2. Create new /etc/resolv.conf
echo "nameserver  172.17.17.10" > /etc/resolv.conf
echo "nameserver  172.17.17.11" >> /etc/resolv.conf

3. Check the backup one
cat /etc/resolv.conf_backup
Gedit is a graphical text editor like notepad but you are trying to start it in an environment without graphics (command line).

Either edit it as suggested above or start the graphics environment.

Author

Commented:
Hi Wesley_Chen

1) I follow the above EXCEPT echo "nameserver  172.17.17.11" >> /etc/resolv.conf (right her, I just type with ONE " > "; I am not sure the right one is ONE  (of ">") or TWO (of " >>")

2) Then, when do " cat /etc/resolv.conf_backup"
- the answer is " search local domain"

3) So, Have I configured the DNS servers at this Centos_5?
- If Yes, How can I know it?

4) Thanks

tjie
Top Expert 2011

Commented:
- echo "nameserver  172.17.17.11" >> /etc/resolv.conf (right her, I just type with ONE " > "
1.
You need ">>" for the second line. Otherwise it will override the first one.
Andy just do it again.

echo "nameserver  172.17.17.10" > /etc/resolv.conf
echo "nameserver  172.17.17.11" >> /etc/resolv.conf

2.
cat /etc/resolv.conf
  to confirm (it's ok for /etc/resolv.conf_backup, nothing need to add to the new one)
Top Expert 2011

Commented:
> : redirect the output to
>> : append the output to

Author

Commented:
Hi Wesley_Chen,

1) I did with ">>" for 172. . .11"
2) Then, I do "  cat /etc/resolv.conf_backup "
- The answer is the same as above --> search local domain

3) Has the nameserver or DNS been configured?
- I believe that it has NOT been configured
- Any comment or confirmation?

4) Thanks

tjie
Top Expert 2011

Commented:
> Then, I do "  cat /etc/resolv.conf_backup "
do
cat /etc/resolv.conf
   NOT (cat /etc/resolv.conf_backup)

Author

Commented:
1) Yes, you are the man

2) When I type: cat /etc/resolv.conf

3) I got the answer:
nameserver 172.17.17.10
nameserver 172.17.17.11

--> so I got the DNS servers for this Centos_5

4) The things that still confused me:
- Why You have to do or to create " /etc/resolv.conf_backup "....and we do not use this "resolv.conf_backup" ----> is it for Security reason?
- the 2nd things that I need your confirmation:
- So to create a new " /etc/resolv.conf ", I can use this formula

 *echo "nameserver  172.17.17.10" > /etc/resolv.conf
 * echo "nameserver  172.17.17.11" >> /etc/resolv.conf

5) Just explain in general a little bit of #4 please
6) Thanks

tjie
Top Expert 2011

Commented:
A4. Yes, it is for security reason in case something wrong and you can roll back the change.

  Say,
  $ echo A
   and it returns
  A
   on the screen

So
echo "nameserver  172.17.17.10"
  returns (whatever within "... " )
nameserver  172.17.17.10
  on the screen

echo "nameserver  172.17.17.10" > /etc/resolv.conf
   It redirect screen output to the file /etc/resolv.conf and override anything in that file (it file not exist, it creates one.)

echo "nameserver  172.17.17.11" >> /etc/resolv.conf
   append "nameserver  172.17.17.10" to  the file, /etc/resolv.conf as second line.

Author

Commented:
Hi Wesley_Chen & Savone:

1) One more related question ...

2) Per Savone,

""" Gedit is a graphical text editor like notepad but you are trying to start it in an environment without graphics (command line). """

3) My question:

- Which editor should I use for it? Nano? Vi?

4) Thanks

tjie
Top Expert 2011

Commented:
vi is everywhere in Unix/Linux world.
nano is easier and popular in modern Linux world.

It's up to you. I use vi.

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