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Re: [Sheflug] IP address via DHCP
It's wonderful how an innocent query can spark off such interesting
discussions. Not that I understood much of them, of course :-) Thanks
to you all for your suggestions. Just a few wee questions then :-)
home@alexhudson.com wrote
>
>> This should be a simple one to answer. I've looked at the man pages for
>> dhcp etc. I've looked in /var/state/dhcp and /etc etc. but I haven't
>> found a good way to get my current IP address.
>
> ifconfig ?
right. thanks Alex, that answered my main concern [tho' I'd hoped for a
command that would give me just the IP address; of course I can filter
the output from ifconfig myself though that would be fragile if the
format changed].
>> On my old system, the hostname was automatically changed to my ipaddress
>> [which wasn't very convenient as I use hostname as part of my prompt
>> string...]
>
> DHCP has a system whereby the server can suggest a name to a client, among
> other things - you could use this. You can also set specific leases to MAC
> addresses - basically, tying the IP address to a specific client. You can
> then set the hostname manually on the client.
via /etc/mactab I guess. Presumably only of use to me if I set up a
home network?
>
>> pc-62-31-17-212-sh.blueyonder.co.uk
>>
>> but instead it was set to just pc-62-31-17-212-sh
>
>
> The first is the fully-qualified name (FQDN), the second is just the
> hostname. Either are valid.
Thanks for the explanation. It isn't a pretty hostname, is it? I guess
I am better off not specifying DHCLIENT_SET_HOSTNAME="yes" in
/etc/rc.config.d/dhcpcd.rc.config [which I think I managed to do via a
highly complicated invocation under Yast2]. Then, for reasons I don't
understand, the problems I mention below to do with resolv.conf don't
arise. Thing is, I quite like the idea of having a fixed hostname of my
choice (say "linux" for the sake of argument) and then being able to
telnet to my machine as linux.blueyonder.co.uk; but I don't see any way
of doing that automatically as it must mean altering some configuration
in the remote machines I use everytime my home machine is rebooted and
possibly gets a new IP address via DHCP. So what I used to do was to
automatically email the hostname set by DHCP at boot time to myself on
my work network and use that; it so happens that the hostname was set to
what you call the FQDN by stuff Gentus did that I didn't understand.
Now I can just email the results of ifconfig to work instead; not as
pretty but it works. Or at least it would...
..if I knew how to do it! Under Gentus (and I guess, Red Hat
generally) there was this nice configuration file called
/etc/rc.d/rc.local into which I inserted the line
mail -n -s `hostname` matt [at] dcs.shef.ac.uk < /etc/rc.d/start.msg
but SuSE doesn't seem to have an equivalent, and although I found plenty
of files controlling different run levels, I couldn't decide where to start.
Are there any other advantages to setting the hostname via DHCP?
> It's likely that in /etc/resolv.conf you would
> have "domain blueyonder.co.uk", which would indicate that pc-62-31-17-212-sh
> is in the domain blueyonder.co.uk (and hence has the FQDN we see above).
I didn't, but if I add a line "domain blueyonder.co.uk" to
/etc/resolv.conf then hostname -f gives the full hostname and most
things seem to work fine after that (such as Gnome, which complains if
the line is missing). The only problem is that dhcpcd overwrites
/etc/resolv.conf, so it seems I should specify the line domain
blueyonder.co.uk in some other file. Trouble is, I don't know which
one. Of course, an obvious suggestion from reading the comments in
resolv.conf [below] is to set DHCLIENT_MODIFY_RESOLV_CONF=no; but I have
no idea what else that might break since I don't understand where the
nameserver settings come from or whether they might change from one
invocation of dhcpcd to another. here is my /etc/resolv.conf in case
it helps:
### BEGIN INFO
#
# Modified_by: dhcpcd
# Backup: /etc/resolv.conf.saved.by.dhcpcd
# Process: /sbin/dhcpcd
# Process_id: 224
# Script:
# Info: This is a temporary resolv.conf created by dhcpcd.
# If you don't like dhcpcd to change your nameserver
settings,
# then either set DHCLIENT_MODIFY_RESOLV_CONF=no in
# /etc/rc.config.d/dhcpcd.rc.config, or set
# MODIFY_RESOLV_CONF_DYNAMICALLY=no in /etc/rc.config,
# or (manually) use dhcpcd with -R.
# If you only want to keep your searchlist, set
# DHCLIENT_KEEP_SEARCHLIST=yes in
# /etc/rc.config.d/dhcpcd.rc.config or (manually) use
# the -S option.
### END INFO
nameserver 62.30.240.177
nameserver 62.30.240.178
search
I get the "search" line by setting DHCLIENT_KEEP_SEARCHLIST="yes" but
where on earth is it searching? Anyway, it isn't finding a domain,
whereever it is looking.
>> which isn't much use as an IP address
>
>
> .. because it's not an IP address?
Fair point. I am confusing domain names with IP addresses. I find that
for ftp, telnet purposes etc. that pc-62-31-17-212-sh.blueyonder.co.uk
works as well as 62.31.17.212 (ok, I admit it is more longwinded and not
easier to remember...)
>> same theme, how do I change the hostname to something other than "linux"?
>
>
> /etc/hostname, among other methods.
Ok, the others have pointed out this doesn't exist on SuSE. Never mind.
>
>
> These commands you also might find useful:
>
> hostname -s ; the short host name
> hostname -f ; the FQDN
Yes, I do, thanks very much.
Matt.
--
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| Matt Fairtlough |
| 22 Harley Road |
| Sheffield S11 9SE UK tel. 0114 236 2067 |
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