[Lxc-users] Regarding creating a LXC container in fedora 17

[Michael H. Warfield]

On Sun, 2013-05-19 at 00:02 +0530, Shridhar Daithankar wrote:
> On Saturday, May 18, 2013 09:58:26 AM Michael H. Warfield wrote:
> > On Sat, 2013-05-18 at 19:02 +0530, Ajith Adapa wrote:
> > > Then I have started the container using below command and tried to
> > > connect to its shell using lxc-console command but I ended up with
> > > below message. Ideally I should see a prompt but its just hangs down
> > > there. <Ctl+a q> works and nothing else.
> > > 
> > > [root at ipiblr ~]# lxc-start -n TEST -d
> > > [root at ipiblr ~]# lxc-console -n TEST
> > > 
> > > Type <Ctrl+a q> to exit the console, <Ctrl+a Ctrl+a> to enter Ctrl+a
> > > itself
> > 
> > Oh, crap...  I keep forgetting about that (because I don't use it).
> > That needs to be noted somewhere in the documentation.
> > 
> > That's yet another BAD decision on the part of the systemd crowd,
> > lxc-console is probably not going to work, at least for the time being.
> > They (systemd) intentionally, with documented malice a forethought,
> > disable gettys on the vtys in the container if systemd detects that it's
> > in a container.  However, /dev/console in the container is still active
> > and is connected to lxc-start and I'm able to log in there but I have
> > never gotten lxc-console to work with a systemd container and I don't
> > know of anything I can do about it.  You would need some way to force
> > the container to start gettys on the vtys.
> > 
> > Maybe, if I (or someone else) can figure out a way to do that (force the
> > gettys to start on the vtys), it could be integrated into the Fedora
> > template.  My patches for the autodev stuff (plus other stuff) have now
> > been accepted and applied by Serge, so that's done.  Maybe I can look
> > deeper into this morass now.

> First of all, let me say thank you for your concise message upthread. It 
> renewed my interest in lxc and I managed to get a working container for the 
> first time. I will post a detailed HOWTO shortly.

> I ran into the same lxc-console issue and managed to solve it by commenting 
> out ConditionPathExists line in 
> /etc/systemd/system/getty.target.wants/getty\@tty1.service

> first I had to start the container in foreground, login, comment out 
> aforementioned line and restart it in daemon mode. After that lxc-console 
> worked.

> If I changed the systemd unit from the chroot itself, it didn't reflect 
> somehow. Also the line referred to /dev/tty0 but only /dev/tty and /dev/tty1 
> were available in the container.

> I don't understand systemd enough to comment on the reasons of it working or 
> not-working. I just experimented around to get a working tty.

Oh, I understand why it's working and that's VERY interesting.  I hadn't
dug into that realm of the systemd files as yet.  They're using the mere
existence of /dev/tty0 as a logic switch to determine if they are going
to start a getty on %I (/dev/tty1 in this case).  Which is yet another
case of them burying a magic cookie switch in the logic.  They
conditionalize it on a hard coded /dev/tty0 but then start a getty
"/sbin/agetty --noclear %I 38400".  the %I is the unit name.  Cute.
Cheeky bastards.

So, it basically means that if we create a tty0 under autodev, that
should then enable any listed vty consoles we set up using systemd
links.  That could be a key to making that work without modifying files
in the container but would require a (relatively minor but non trivial)
change to the lxc source code, as opposed to merely a template.  I'll
run this up the flagpole on the -devel list and with Serge and get their
opinions.  This is doable.  I think I'll try this out in my sources
first and then post a request for comments over on -devel.  The problem
is in the routine "setup_tty" in conf.c that's going to need some
massaging to make it 0 based instead of 1 based and adjust for the
additional tty count.  :-/

> My environment is arch linux and the details are as follows.

> kernel : 3.9.2-1 
> systemd : 204-1
> lxc : 1:0.9.0-2
> 
> HTH
> 
> -- 
> Regards
>  Shridhar
> 

-- 
Michael H. Warfield (AI4NB) | (770) 985-6132 |  mhw at WittsEnd.com
   /\/\|=mhw=|\/\/          | (678) 463-0932 |  http://www.wittsend.com/mhw/
   NIC whois: MHW9          | An optimist believes we live in the best of all
 PGP Key: 0x674627FF        | possible worlds.  A pessimist is sure of it!
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