On Wed, 26 Nov 2003, A.J. Bonnema wrote:
> Alexander Dalloz wrote:
> >
> > Hopefully you have not deleted the localhost entry in /etc/hosts,
> > otherwise sendmail and some other applications will not work properly.
> >
> > 127.0.0.1 localhost.localdomain localhost
> >
> > has to be there in every case
>
> Well actually, originally I did, because I didn't have any use for this
> entry. However, I was quickly convinced this was not a wise decision
> following the errors I got.
>
> Anyway, thanks for the tip.
Another tip for those using DNS is to have a caching server and/or a
local to the box SOA authority for localhost. See named or nscd.
It is usefull to snoop on the wire once in a while and discover if
too many DNS lookups for localhost/127.0.0.1 go out over the wire to
your ISP. Lots of X-window connections involve a lookup and
connection to localhost if these are not cached or are slow
windows will open slowly.
Next the host file is commonly looked at from top to bottom and as
soon as a line with a match is found no additional searching is
done. One message in this thread apprently had a double line:
127.0.0.1 localhost.localdomain localhost
127.0.0.1 turtle.localdomain turtle
Which may not act the same as
127.0.0.1 localhost.localdomain localhost turtle.localdomain turtle
depending on how the resolver code works and what is desired.
Also watch for multiple host files generated by different tools
where the info might get out of sync (dbm files?). Examples:
/etc/sysconfig/networking/profiles/default/hosts
/etc/hosts
/etc/samba/lmhosts
Check also /etc/resolv.conf /etc/host.conf (see "man resolver") If
one of the hosts in resolv.conf is unavailable it takes a long time
for the timeout. Watch for DNS timeouts and if necessary reorder or
improve the list of DNS hosts
BTW: one of the RH-9 GUI triggered tools will rewrite the host file
inside out thus:
127.0.0.1 localhost.localdomain localhost
192.168.0.51 h51.hobblehead.com h51.hobblehead h51 sometimes
is rewritten something like:
localhost.localdomain 127.0.0.1 localhost
h51.hobblehead.com 192.168.0.51 h51.hobblehead h51
When I find the tool that does this I will file a bug....
LDAP, NIS, winbind are additional tangles, keep it simple...
