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hostid command outputs 0, how to generate hostid on Redhat Linux 4.6

Posted on 2008-10-10
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Last Modified: 2013-12-06
We have a Redhat Linux 4.6 OS on HP DL585 G5 , hostid command outputs 0,
How to generate the hostid, or what should be done in this case, to have hostid setup.

Thanks in advance.
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Question by:solven3
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8 Comments
 
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omarfarid earned 672 total points
ID: 22687439
I am not sure how hostid get generated, but I have seen some comments on this on the Internet where it says that it is related to host ip address. What is the ip address of your system?

http://osdir.com/ml/user-groups.linux.madurai.general/2005-04/msg00023.html

Other page says it is related to the mac address:

http://www.mathworks.com/support/solutions/data/1-171PI.html?solution=1-171PI
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by:jools
jools earned 664 total points
ID: 22687491
running strace seems to indicate /etc/hosts is used, I just moved my /etc/hosts out the way and got this;

# hostid
00000000

moving it back and tunning it again;
# mv /etc/hosts.old /etc/hosts
# hostid
007f0100



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Expert Comment

by:omarfarid
ID: 22687519
So it is related to IP address and may be entry in /etc/hosts file
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by:jools
ID: 22687564
May also be something in the dns, mine just looked at the order in the hosts.conf and other files.

List of files ripped from the strace log are;

open("/etc/ld.so.cache", O_RDONLY)      = 3
open("/lib/libc.so.6", O_RDONLY)        = 3
open("/usr/lib/locale/locale-archive", O_RDONLY|O_LARGEFILE) = 3
open("/etc/hostid", O_RDONLY|O_LARGEFILE) = -1 ENOENT (No such file or directory)
open("/etc/resolv.conf", O_RDONLY)      = 3
open("/etc/nsswitch.conf", O_RDONLY)    = 3
open("/etc/ld.so.cache", O_RDONLY)      = 3
open("/lib/libnss_files.so.2", O_RDONLY) = 3
open("/etc/host.conf", O_RDONLY)        = 3
open("/etc/hosts", O_RDONLY)            = 3
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Assisted Solution

by:Mysidia
Mysidia earned 664 total points
ID: 22691705
It appears to me that hostid does the following:

1. calls gethostname() [i.e. takes the hostname given by the output of the 'hostname' command in the shell]

2. Finds the entry in /etc/hosts that corresponds to the ip address of the hostname.

3. Copies octets from the ip address and prints them as a hex number:
AA.BB.CC.DD ==> 0x[BB][AA][DD][CC]

for example, if my hostname is 'foobar.example'

and my entry in /etc/hosts says

127.0.0.1 foobar.example

Then the hostid command prints '007f0100'



So to make 'hostid' not print zero... type the 'hostname' command after boot

Make sure there is an entry in /etc/hosts for that name.

Make sure that entry corresponds to a good ip address.

If you want the output to be unique, don't use 127.0.0.1



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