Re: /lib/systemd/systemd-hostnamed hang
On Sat, Nov 24, 2012 at 6:27 PM, Zenaan Harkness <zen@freedbms.net> wrote:
> On 11/25/12, Michael Biebl <biebl@debian.org> wrote:
>> On 24.11.2012 14:40, Tom H wrote:
>>> On Sat, Nov 24, 2012 at 6:02 AM, Zenaan Harkness <zen@freedbms.net>
>>> wrote:
>>>>
>>>> Any idea how to make use of systemd-hostnamed?
>>>>
>>>> Eg:
>>>> $ sudo /lib/systemd/systemd-hostnamed
>>>> Warning: nss-myhostname is not installed. Changing the local hostname
>>>> might make it unresolveable. Please install nss-myhostname!
>>>> # hang's at this point, apparently indefinitely...
>>>
>>> What are you expecting it to do?
>>
>> It doesn't hang. It is a system daemon which just waits sits there and
>> waits for requests (via D-Bus).
>>
>> Nothing unexpected here aside from starting this tool directly.
>>
>> It would be like starting apache by hand and then wondering that it sits
>> there waiting for requests via port 80.
>
> Thanks for the clarifications.
>
> $ lighttpd --help
> lighttpd: invalid option -- '-'
> lighttpd/1.4.31 (ssl) (Jul 14 2012 12:10:48) - a light and fast webserver
> usage:
> -f <name> filename of the config-file
> -m <name> module directory (default: /usr/lib/lighttpd)
> -p print the parsed config-file in internal form, and exit
> -t test the config-file, and exit
> -D don't go to background (default: go to background)
> -v show version
> -V show compile-time features
> -h show this help
>
> $ /lib/systemd/systemd-hostnamed --help
> This program takes no arguments.
>
> $ man lighttpd
> #...
>
> $ man systemd-hostnamed
> No manual entry for systemd-hostnamed
>
> I guess, being a "boot time" program and possibly headed for
> inclusion-in-initrd territory, the intent is to keep "core" daemons as
> small as possible, and not encumbered with memory consuming --help
> option?
>
> For discoverability/learnability of such things, should I be saying
> "the source code is the man page"?
>
> Or should I simply ignore all binaries in /lib/ ?
>
> >From /usr/share/doc/systemd/README, :
> "When systemd-hostnamed is used it is strongly recommended to
> install nss-myhostname to ensure that in a world of
> dynamically changing hostnames the hostname stays resolveable
> under all circumstances. In fact, systemd-hostnamed will warn
> if nss-myhostname is not installed. Packagers are encouraged to
> add a dependency on nss-myhostname to the package that
> includes systemd-hostnamed."
>
> Perhaps the lack of libnss causes the big delays when starting xterm
> after changing hostname?
>
> Ought there be an addition to man hostname, suggesting that updating
> hostname with /bin/hostname, and/ or with /etc/hostname edit, should
> be accompanied with an address resolvability update to /etc/hosts in
> order to avoid long timeouts when starting applications (perhaps just
> under X?) ??
>
> apropos hostname
> man 5 hostname
> # still no suggestion that changing hostname may cause resolver delays
> man 7 hostname
> # this possibly gives a bit of a hint
> (please note, I totally forgot about apropos until just now)
>
> What I am getting at here is the issue of (lack of) discoverability
> regarding this hostname-causing-application-startup-delays issue and
> how to fix it.
>
> debian-user is a great fallback. It ought to be possible, when someone
> in the future asks a similar question, that we can point the newbie to
> say
>
> man hostname
> # and read paragraph 3
>
> or say:
>
> apropos hostname
> man 5 hostname
> # and read paragraph 3
>
> or some such.
>
> I attempted to discover/solve my problem/annoyance (10+ seconds xterm
> startup delays), but was not able to solve the problem with the
> references to the systems documentation which I tried, and I don't
> seem to see any clarity on this from man 5 or man 7 either.
>
> I am very grateful for the abundant documentation we have, and would
> like to see a little more, if that is a good idea in this case.
>
> A rough initial draft for an extra paragraph in man 1 hostname or man
> 5 hostname:
>
> WARNING (or CAUTION, or under NOTES ?)
> Changing the hostname during runtime, without the new hostname being
> resolvable to an ip address can cause delays when starting applications
> which are in any way linked to the resolver(5).
> This is the case for most(all?) X applications
>
> Suggestions appreciated, and when we have satisfactory wording, we can
> forward the suggestion to hostname-devel@lists.alioth.debian.org, and/
> or create a bug against hostname package? Guidance appreciated.
The latest version of system has hostnamectl and a man page for
systemd-hostnamed.
Even if you weren't using systemd, you would've had the xterm problem
because you removed the standard "127.0.1.1 ..." line from
"/etc/hosts", although I'm not sure how xterm would behave with the
hostname known by the kernel being different from the one on the
"127.0.1.1" line.
Anyway, AFAIU, systemd-hostnamed is there to provide an interface for
GUIs to change the hostname. At the CLI, "hostname <new-hostname>"
(and other changes should the new name have to be persistent) are
still the way to go - unless you have a version of systemd with
hostnamectl.
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