Installing second dhcp/dns server
I have a two node eDirectory environment. One server is at OES2018 SP2 while the other server is still at SLES 11 SP4 / OES 2015 SP1. The OES 2015 SP1 server has an OES DHCP and DNS server running on it while the OES 2018 server doesn't. Before I migrate the OES 2015 server to 2018 SP2, I want to add a second DNS/DHCP server running on the OES 2018 server. I have read the docs but they are not not clear (at least to me) on some of issues.
1. On the OES 2015 server, the previous consultant had both an OES DHCP server installed as well as the SLES DHCP server. They claimed both had to be installed and running. My understanding is that just the OES DHCP server is needed for DHCP for the network, is that correct?
2. When starting the install of the DHCP server on the OES 2018 server, there are a number of parameters that Yast asks for during the install. The DHCP Server Context, Locator context and group context - can they be the same as the DHCP server that is already running on the OES 2015 server?
3. Can I just install DNS without DHCP on the OES 2018 server or doe they have to be installed together?
4. For the runtime credentials of the DHCP server, I assume that the OES 2015 DHCP server has runtime credentials but I don't know what they are. Can I have different runtime credentials for the OES 2018 DHCP server?
5. Is there any way to just copy or duplicate the DHCP and DNS server on the OES 2015 server to the OES 2018 server? Basically I just want redundancy for these two services so if a server is down, I still have DHCP and DNS.
It's as simple as you think.
A: you can have two dns servers, just let yast fetch the dns parameters from the other server and let yast create the dns server.
B: Do exactly the same for dhcp, let yasy fetch the parameters.
In the dns/dhcp console, you can select which server is running dhcp in the dhcp tab, just select the new one. stop dhcp on the old server and start it at the new server.
Thanks, Alex. just to be clear, to install DNS on the 2018 SP2 server, I load Yast, then go to Network Services, then click 'DNS Server'? The prompts here don't agree with what I read in the "OES 2018 SP2: DNS/DHCP Services for Linux Administration guide".
You need to configure dns and dhcp from the oes installation and configuration option in yast2:
select novell dhcp and novell dns
after accept, for dns thick the get context
Have got the scfreens shots for dhcp, but you should be able to fetch with a tickbox and entering the existing dhcp server
One god, one country, one wife, one DHCP server instance per box.
Yep. Anything other will likely harm.
No need to install both of them if you just need one.
You should use the CommonProxyUser, which is server-centric. So don't select another server's CommonProxyUser.
It's always wise to have at least two DNS instances running which serve the same subnets. For DHCP it's somewhat more complicated in a non-cluster offset. You'd need to configure e.g. split-subnets or create a failover peer offset. Please note that dynamic leases aren't stored in eDir with OES Linux, so if you have a DHCP server running "on standby", it won't be aware of existing dynamic leases if you let it take over manually.
Thanks a lot. I followed your info and was able to install both DNS and DHCP. When installing DHCP I got the error that there was a conflict with pattern:novell-dhcp-12.1-43.1x86_64. I chose the conflict resolution to deinstall dhcp-client-4.3.3-10.16.4.x86_64. I have seen these messages before and it is VERY confusing. There is no info on what the 'normal' or 'correct' thing is to do and no info on what the ramifications are of any of the choices. I have attached a screen shot. Notice how in this day and age, MicroFocus can't wrap the text of the error to fit in the window and/or can't make the window resizeable so you can see the whole error. I think that is ridiculous.
Also, after the install, I was able to find novell-named in Services Manager and enable it so it starts when the server starts. I did not see a similar 'novell-dhcpd' option. There is a service called 'dhcpd' and the description is "ISC DHCPv4 Server". Is this the native Linux DHCP or is this the OES DHCP that I just installed??? It is currently disabled.
Also, with DHCP, I wouldn't want two DHCP servers handing out IP addresses at the same time, would I? Don't I have to have one DHCP server hand out IP addresses in one range and the other hand out IP addresses in another range? We are using a class C subnet in our office. Or does the fact that these are integrated with eDir make it so both DHCP servers could be active?
My overall goal is to make it so I can take one server down and users can still get an IP address and still have DNS functioning.
The conflict is a result of having BOTH SLES and OES DHCP patterns installed on the source box. The decision how to handle this is up to the admin (an installation script should never do this, how can it know what YOU want..). And your decision was perfectly fine as you now have "novell-oes-dhcp-client" installed.
As for the daemon name: it's the correct one. rcnovell-dhcpd starts "/usr/sbin/dhcpd".
As for the rest: see my other post. You don't want to have two instances servicing the same pool without further configuration. This one should give you an idea regarding failover peers.
Thanks Mathais. That makes sense. I have the DHCP server on the second box installed but not running. Do you know what an OES DHCP server should show up as in the Run Services app? I can't find it.
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Do you mean "yast -> system -> services manager"? It'll likely show up twice as
"dhcpd" and "dhcp-server".
systemctl enable dhcpd
will do anything you need and take care of both.