[CentOS] sudo doing DNS lookup

[Steve Clark]

On 12/10/2010 10:40 AM, Tom H wrote:
> On Fri, Dec 10, 2010 at 8:43 AM, Steve Clark<sclark at netwolves.com>  wrote:
>    
>> I have a confusing problem. I have two centos 5,5 boxes. Both have
>> sudo.i386                                1.7.2p1-9.el5_5
>> installed
>>
>> I am using the same sudoers file, but the one on box A keeps trying to do
>> DNS lookups while the one on box B does not. How do I disable this DNS
>> lookup?
>>      
>    

> Do both hosts have their hostnames in "/etc/hosts"?
>
> Do both hosts have "hosts: files dns" in "/etc/nsswitch.conf"?
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>    

strace shows the  DNS lookup.

I have resolved the problem as far why they behaved differently.
Someone had put an entry in /etc/resolv.conf when normally we run our
own nameserver at 127.0.0.1.
Putting a hostname and address in the /etc/hosts also fixed the problem.

But I still don't understand why it wants to do a DNS lookup when I don't
have
Defaults fqdn
in the sudoers file.

Again here is part of an strace of sudo cat /etc/rc.local;

...
socket(PF_INET, SOCK_DGRAM, IPPROTO_IP) = 4
connect(4, {sa_family=AF_INET, sin_port=htons(53), 
sin_addr=inet_addr("127.0.0.1")}, 28) = 0
fcntl64(4, F_GETFL)                     = 0x2 (flags O_RDWR)
fcntl64(4, F_SETFL, O_RDWR|O_NONBLOCK)  = 0
gettimeofday({1292009049, 862615}, NULL) = 0
poll([{fd=4, events=POLLOUT}], 1, 0)    = 1 ([{fd=4, revents=POLLOUT}])
send(4, "\206r\1\0\0\1\0\0\0\0\0\0\5Z7070\tnetwolves\3com"..., 37, 
MSG_NOSIGNAL) = 37
poll([{fd=4, events=POLLIN}], 1, 5000)  = 1 ([{fd=4, revents=POLLIN}])
ioctl(4, FIONREAD, [86])                = 0
recvfrom(4, "\206r\205\203\0\1\0\0\0\1\0\0\5Z7070\tnetwolves\3com"..., 
1024, 0, {sa_family=AF_INET, sin_port=htons(53), 
sin_addr=inet_addr("127.0.0.1")}, [16]) = 86
close(4)                                = 0
socket(PF_INET, SOCK_DGRAM, IPPROTO_IP) = 4
connect(4, {sa_family=AF_INET, sin_port=htons(53), 
sin_addr=inet_addr("127.0.0.1")}, 28) = 0
fcntl64(4, F_GETFL)                     = 0x2 (flags O_RDWR)
fcntl64(4, F_SETFL, O_RDWR|O_NONBLOCK)  = 0
gettimeofday({1292009049, 864056}, NULL) = 0
poll([{fd=4, events=POLLOUT}], 1, 0)    = 1 ([{fd=4, revents=POLLOUT}])
send(4, "\324\305\1\0\0\1\0\0\0\0\0\0\5Z7070\tnetwolves\3com"..., 51, 
MSG_NOSIGNAL) = 51
poll([{fd=4, events=POLLIN}], 1, 5000)  = 1 ([{fd=4, revents=POLLIN}])
ioctl(4, FIONREAD, [100])               = 0
recvfrom(4, 
"\324\305\205\203\0\1\0\0\0\1\0\0\5Z7070\tnetwolves\3com"..., 1024, 0, 
{sa_family=AF_INET, sin_port=htons(53), 
sin_addr=inet_addr("127.0.0.1")}, [16]) = 100
close(4)                                = 0
readlink("/proc/self/exe", "/usr/bin/sudo"..., 4095) = 13







-- 
Stephen Clark
*NetWolves*
Sr. Software Engineer III
Phone: 813-579-3200
Fax: 813-882-0209
Email: steve.clark at netwolves.com
http://www.netwolves.com
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