'sudo -i' and resolve host

brownflamigo1 · 03-10-2011, 05:58 AM

I tried searching online, but that did not produce any results.
Could anyone please explain to me, why does a machine try to resolve host when I issue 'sudo -i' or some other command prefixed with sudo.
What is happening in the background?

Thanks.

corp769 · 03-10-2011, 11:40 AM

Can you explain more of what exactly you are doing?

brownflamigo1 · 03-11-2011, 04:12 AM

DNS server went down. And when I issue 'sudo -i' I notice that the (Debian) machine tries to resolve it's hostname.
The question is: why would it need to resolve a hostname, when issued a 'sudo -i' command. I miss to see the connection between two events...

corp769 · 03-11-2011, 04:23 AM

Do you have any output of it? And does it try to resolve when you just issue su - ?

brownflamigo1 · 03-12-2011, 06:13 AM

user@host:~$ sudo -i
sudo: unable to resolve host host

su -
requests me to enter root password, but does not display this message.

corp769 · 03-12-2011, 09:11 AM

Definitely something within your environment variables or something within that nature that is doing this. I would recommend going through them to see what is causing it.

---------- Post added 03-12-11 at 04:12 PM ----------

From the man page -

Quote:

The -i (simulate initial login) option runs the shell specified in
the passwd(5) entry of the user that the command is being run as.
The command name argument given to the shell begins with a - to
tell the shell to run as a login shell. sudo attempts to change to
that user’s home directory before running the shell. It also ini‐
tializes the environment, leaving TERM unchanged, setting HOME,
SHELL, USER, LOGNAME, and PATH, and unsetting all other environment
variables. Note that because the shell to use is determined before
the sudoers file is parsed, a runas_default setting in sudoers will
specify the user to run the shell as but will not affect which
shell is actually run.

repo · 03-12-2011, 09:13 AM

Please post the output from

Code:

cat /etc/hosts

Kind regards

brownflamigo1 · 03-13-2011, 08:25 AM

Quote:

Originally Posted by corp769

Definitely something within your environment variables or something within that nature that is doing this. I would recommend going through them to see what is causing it.

---------- Post added 03-12-11 at 04:12 PM ----------

From the man page -

I went through the contents of .profile, .login and .bashrc as well as checked the environment variables, but could not find anything that points to the host resolution process.

<user>@<domain>:~$ cat /etc/hosts
# This file is managed by cfengine
127.0.0.1 localhost.localdomain localhost
2001::XX mea.<domain>
2001::XX coo.<domain>
2001::XX kwa.<domain>
2001::XX fru.<domain>
# The following lines are desirable for IPv6 capable hosts
::1 ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
ff02::3 ip6-allhosts

And here are the contents of resolv.conf:

<user>@<domain>:~$ cat /etc/resolv.conf
# This file is managed by cfengine
search net.<domain> eec.<domain> <domain>
nameserver 2001::XX

repo · 03-13-2011, 08:29 AM

try to comment everything out except

Code:

127.0.0.1 localhost.localdomain localhost

in /etc/hosts

comment out

Code:

nameserver 2001::XX

in
/etc/resolv.conf

Kind regards

brownflamigo1 · 03-13-2011, 08:34 AM

If I comment out the "nameserver 2001::XX" in resov.conf and comment out everything in hosts, except for the IPv4 localhost, then I get the message again:

Quote:

<user>@<host>:~$ sudo -i
sudo: unable to resolve host <host>

repo · 03-13-2011, 08:37 AM

and if you comment out

Code:

search net.<domain> eec.<domain> <domain>

Kind regards

brownflamigo1 · 03-13-2011, 08:43 AM

I get the same message ("Unable to resolve...") if I comment out either just the 'net.<domain> eec.<domain> <domain>' line or both lines in resolv.conf.