Name or service not known

Question

I have been trying to get the ipaddress of the person who logged into the machine using the below code but I get a error.

>>> import socket
>>> socket.gethostbyname_ex(socket.gethostname())
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
socket.gaierror: [Errno -2] Name or service not known

The same code works in other linux box. Not sure I fix it.

Is the output of `socket.gethostname()` the same as if you run `echo $HOSTNAME` on Bash ? Also, can you post your `/etc/hosts` file? — Bernardo Meurer, Jul 07 '16 at 20:17
https://docs.python.org/2/library/socket.html#socket.gethostname - that's the hostname of your local server, nothing to do with the person who logged into the machine. And the documentation warns that you can't `gethostbyname` on the result, if there is no host to IP mapping. In short, your server is misconfigured and your code doesn't do what you want. — TessellatingHeckler, Jul 07 '16 at 20:21
"if there no host to IP mapping" --how do I fix that?..I have other servers thats working perfectly fine with the same code — user1050619, Jul 07 '16 at 20:26
127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4 ::1 localhost localhost.localdomain localhost6 localhost6.localdomain6 127.0.0.1 scratch — user1050619, Jul 07 '16 at 20:36
Hm. That seems alright. What happens if you `traceroute $HOSTNAME`? — Bernardo Meurer, Jul 07 '16 at 20:46
It worked now, earlier the hostname and the host name in the /etc/hosts file was not in sync..Thanks much guys. — user1050619, Jul 07 '16 at 21:08

score 4 · Answer 1 · answered Oct 25 '17 at 07:03

4

Error has occurred just because of not setting up hostname properly. Set the hostname at three different places, which are in -

/etc/hostname

/etc/hosts

run command $ hostname

then logout and login again. You are done.

answered Oct 25 '17 at 07:03

Yogesh Jilhawar

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score 0 · Answer 2 · answered Jul 07 '16 at 20:16

Check what is being returned by socket.gethostname() and see if you can ping it. Basically this is a lookup failure. Check your /etc/hosts to see if it is listed. I know it seems strange, but I think if the hostname being returned does not have an entry, you'll get a name service failure which is what that is.

score 0 · Answer 3 · answered Dec 31 '17 at 12:26

If you are working with IPv6 or with servers with multiple network interfaces, this command will not work correctly.

Instead, you can use this command that tries to connect to the Google DNS server at 8.8.8.8 at port 53, and return your ip:

import socket
print([(s.connect(('8.8.8.8', 53)), s.getsockname()[0], s.close()) for s in [socket.socket(socket.AF_INET, socket.SOCK_DGRAM)]][0][1])

Name or service not known

3 Answers3

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