Re: [vserver] localhost - The Cliff Notes version?

Daniel Hokka Zakrisson wrote:
> Roderick A. Anderson wrote:
>> Daniel Hokka Zakrisson wrote:
>>> Roderick A. Anderson wrote:
>>>> OK, I'm sorry to open this can of worms again but I can't get my head
>>>> wrapped around the localhost (127.0.0.1) in guests thing.
>>>>
>>>> I have guests running PostgreSQL and postfix. Both _would_ like a (or
>>>> rather pitch a bitch if there is no) localhost entry when they are
>>>> installed or an attempt is made to start them.
>>>>
>>>> I've hacked my way through this but I think from watching this list
>>>> there must be an easier way to get around the messages/errors.
>>>>
>>>> So in "user-dummy{1}" terms can anyone offer a solution to making
>>>> localhost auto-magically work?
>>>>
>>>> I see that all the 127.0.0. IPs ping from inside a guest but I don't
>>>> want to do anything that will cause the host or other guests to die or,
>>>> for that matter, the universe to end if I just put a "localhost" entry
>>>> in /etc/hosts.
>>> It's really very simple. For Linux-VServer versions <2.3, 127.0.0.1 is
>>> rewritten on connect/bind to the guest's first IP address. If
>>> CONFIG_VSERVER_REMAP_SADDR is set, the source address will be rewritten
>>> as
>>> well (for connect). Only applications that have hardcoded checks using
>>> getsockname/getpeername against 127.0.0.1 will ever notice it happened.
>>>
>>> For Linux-VServer versions >=2.3, there is a separate lback address. If
>>> CONFIG_VSERVER_AUTO_LBACK is enabled, the assignment is handled
>>> automatically. The lback address is used, just like in the older
>>> versions,
>>> when binding or connecting to 127.0.0.1. It's remapped for both source
>>> and
>>> destination addresses, and, this is the big difference vs. <2.2, it's
>>> remapped back to 127.0.0.1 whenever userspace asks. This is supposed to
>>> be
>>> completely invisible to userspace.
>> OK I have "cat /proc/vserverion":
>>
>> Linux version 2.6.22.10-vs2.3.0.29.1 (mockbuild@x86.builders.hozac.com)
>> (gcc version 4.1.1 20070105 (Red Hat 4.1.1-52)) #1 SMP Wed Oct 31
>> 10:48:21 EDT 2007
>
> You might want to upgrade to 2.6.22.18-vs2.3.0.32.1 ;-)

Darn. I did a yum update last night be didn't reboot the server. Still
it is only to 2.6.22.10-vs2.3.0.29.1 and I see the latest version on the
repository. Time to do some yum checking.

>
>> Sounds better all the time. Is this set (or how do I check) in the
>> kernels you're building?
>
> grep CONFIG_VSERVER /boot/config-`uname -r`

Excellent. It is there.

>
>> And so I'm thinking the errors I'm seeing are in reaction to no entry in
>> /etc/hosts for localhost or /etc/hosts does not exist.
>
> If that's the case, sure. It could also be due to a strange configuration
> in my kernels before 2.6.22.14-vs2.3.0.29.1, where AUTO_SINGLE would break
> AUTO_LBACK.

I'll continue my research and testing.

Thanks.
Rod

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