not able to update nameserver

SarahGurung · 10-18-2011, 01:08 AM

hello everyone,

when i tried to update my nameserver today,i got an error sayin:

cannot retrieve the mirrorlist http://mirrorlist.centos.org,urlopen...#39;connection timed out')

So what does this mean and what should i be doing now?

aazkan · 10-18-2011, 01:24 AM

Hi,

Couple of things to try, top of my head:

1. Is your /etc/resolv.conf pointed to your own nameserver? Perhaps point it out to Google's dns or opendns and try yum again.

2. Try using links or copy paste the url to your browser (IE,Chrome etc). To use links, access the url like so

links http://mirrolist.centos.org

if it returns a 404, CentOS mirrors could be unreachable at this time (maintenance, network latency etc)

3. If the URL is reachable, try the following on the machine your ran yum

yum clean all
yum check-update

SarahGurung · 10-18-2011, 01:31 AM

well i opened that url http://mirrorlist.centos.org as you said but it didnt return any error and opened easily and ya i did yum clean all and then yum check-update after that but i still got the same thing...

aazkan · 10-18-2011, 01:35 AM

I've come across this before but am not sure if how i solved it will work out for you but if you dont mind trying, I'll help out.

For starters, can you copy paste the actual error message you get when running yum?

also if you dont mind

lsb_release -a
uname -rmi

SarahGurung · 10-18-2011, 01:45 AM

well this is the exact error that i get when i run yum check-update command:

Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
Could not retrieve mirrorlist http://mirrorlist.centos.org/?releas...86&repo=addons error was
[Errno 4] IOError: <urlopen error (110, 'Connection timed out')>
Error: Cannot find a valid baseurl for repo: addons

and when i did uname -rmi,it gave:
2.6.18-238.19.1.el5.centos.plusPAE i686 i386

and with lsb_release -a.it gave:
LSB Version: :core-4.0-ia32:core-4.0-noarch:graphics-4.0-ia32:graphics-4.0-noarch

rinting-4.0-ia32

rinting-4.0-noarch
Distributor ID: CentOS
Description: CentOS release 5.6 (Final)
Release: 5.6
Codename: Final

thanks...

aazkan · 10-18-2011, 01:59 AM

Can you try

yum --disableplugin=fastestmirror check-update -d6

Also, if you don't mind can you copy paste your /etc/resolv.conf?

aazkan · 10-18-2011, 02:01 AM

Oh yes, just crossed my mind, is there a http proxy up front of that CentOS box? If there is you'd probably want to set yum to use it or export the http_proxy variable.

SarahGurung · 10-18-2011, 03:10 AM

well can you please tell me what is the use of "yum --disableplugin=fastestmirror check-update -d6" command?because i have totry it on a live server and cant use it unless i'm very sure about what the command really does....please don't mind...

and i didnt understand what you meant by http proxy and all that...can you please elaborate on that?

Thank you..

aazkan · 10-18-2011, 03:30 AM

--disableplugin=fastestmirror

tells yum not to use the fastestmirror plugin

check-update

tells yum check update

-d6

tells yum to run with debug or more verbose

Sarah, if you're not comfortable then don't run any of the commands i've input. No harm to be paranoid.

In my LANs, no servers can access ftp, http and other ports directly (to prevent shell users or if the server is compromised) to download anything. The traffic going out is purposely not NATed or Masqueraded out.

So to allow something like yum which needs to access http, i need to export a http_proxy variable to yum so it knows to use a squid http proxy somewhere in my LANs.

If you're not using a http proxy then it's safe to ignore the suggestion as well. I'm betting it has to do with a http proxy or perhaps on the isp side.

SarahGurung · 10-18-2011, 03:57 AM

ell my boss isn't here and cant contact him either....i think he has used http proxy as he is really concerned with the securities,if so how should i be exporting the http variable or is there a way to know if http proxy is being used??

and you also told about the isp side?what could be wrong in the isp side?

deep27ak · 10-18-2011, 04:19 AM

Is your yum configured properly on the system?

are you able to install any other package using yum

please check with any package

and

also lookout for

Quote:

#vi /etc/resolv.conf
(post the output)

SarahGurung · 10-18-2011, 04:25 AM

yes,i am able to install other things using yum...

aazkan · 10-18-2011, 04:30 AM

if there is a http proxy that needs to be use, before running yum do this

export http_proxy=http://x.x.x.x:1234/; export ftp_proxy=http://x.x.x.x:1234/

when you're done do

unset http_proxy; unset ftp_proxy

i'm assuming you're using bash

About the isp, in one of our co-los, the isp puts a transparent http proxy, was a cisco webcache or something. The cache was dirty or stale. Once we get them to remove us (routing) from the being http cached transparently, yum worked nicely since.

deep27ak · 10-18-2011, 05:55 AM

if you are using any proxy server then

do the following

Code:

#vi /etc/yum.conf
in the [main] section at the bottom write
http_proxy=http://(your_proxy_address):(port no.)
export http_proxy=http://your_proxy_address:(port)

then go to

Code:

#vi /root/.bash_profile
(add this in the last line)
export http_proxy=http://your_proxy_address:(port)

thats it
now try using yum

SarahGurung · 10-18-2011, 06:12 AM

well previously we were using proxy server which was untangle but now we have removed that one...

so what could be the other possible reasons for not being able to use "yum check-update" command in our primary name server(ns0)??