Create log file in lxcpath for non-system containers

Create log file in lxcpath for non-system containers

On Fri, 26 Apr 2013 10:18:12 -0500
Serge Hallyn <serge.hallyn@ubuntu.com> wrote:

> Quoting Dwight Engen (dwight.engen@oracle.com):
> > On Fri, 26 Apr 2013 09:37:49 -0500
> > Serge Hallyn <serge.hallyn@ubuntu.com> wrote:
> >
> > > Quoting Dwight Engen (dwight.engen@oracle.com):
> > > > Using lxc configured with --enable-configpath-log, and
> > > > specifying a path to the lxc commands with -P, the log file
> > > > path is generated with a basename of LOGPATH instead of the
> > > > lxcpath. This means for example if you do
> > > >
> > > > lxc-start -P /tmp/containers -n test01 -l INFO
> > > >
> > > > your log file will be
> > > >
> > > > /var/lib/lxc/test01/test01.log
> > > >
> > > > I was expecting the log to be /tmp/containers/test01/test01.log.
> > > > This is particularly confusing if you also have test01 on the
> > > > regular lxcpath. The patch below changes the log file path to be
> > > > based on lxcpath rather than LOGPATH when lxc is configured with
> > > > --enable-configpath-log.
> > > >
> > > > I think that even in the normal non --enable-configpath-log case
> > > > we should consider using lxcpath as the base and not having
> > > > LOGPATH at all, as attempting to create the log files
> > > > in /var/log is not going to work for regular users on their own
> > > > lxcpath. If we want that, I'll update the patch to do that as
> > > > well.
> > >
> > >
> > > Perhaps we should do:
> > >
> > > 	1. If lxcpath == default_lxc_path(), then first choice is
> > > 	   LOGPATH, second is lxcpath/container.log
> > > 	2. when opening, if first choice fails, use second choice
> > > 	   if there is any.
> > >
> > > That way 'system' containers will go to /var/log/lxc, as I think
> > > they should.  Custom-lxcpath containers should never go
> > > to /var/log/lxc, since their names could be dups of containers in
> > > default_lxc_path(). And if the system is a weird one where
> > > default_lxc_path is set up so that an unprivileged user can use
> > > it, then we should log into $lxcpath.
> >
> > That sounds good to me. So these rules would apply in both the
> > regular and --enable-configpath-log cases.

I updated the patch to try to open the log file according to the
choices given above. Along the way I cleaned up log.c a bit, making
some things static, grouping external interfaces together, etc...
Hopefully that doesn't add too much noise.

> > > (Note this patch will trivially conflict with my new lxc_clone.c
> > > causing it to fail to build - unfortunate result of timing)
> >
> > Yeah unfortunately this touches every lxc_log_init() caller. I can
> > work on the above logic and re-submit after your new lxc_clone
> > stuff goes in.
>
> No no, I'll just need to remember to update mine.  Don't hold up on
> mine, this is just the nature of such collaboration  :)
>
> > Did you have any thoughts on the XXX what to pass in for lxcpath in
> > lxc_init? Right now it just falls back to LOGPATH.
>
> No - that's a weird one, since lxc_init runs in the container.  If
> there were only system containers I'd say always use LOGPATH.
> However there are people (apparently :) who use container sharing the
> host's rootfs...
>
> lxc-execute does know the lxcpath.  Perhaps we can simply have
> src/lxc/execute.c:execute_start() look at handler->conf to see if a
> rootfs is set.  If rootfs is NOT set, then pass lxcpath along to
> lxc-init.  Then lxc-init can mostly do the same as the others?  (It
> doesn't use src/lxc/arguments.c, so you'd have to add lxcpath to
> options[] in lxc-init.c)

So I did this, only to realize that lxc-init is passing "none" for the
file anyway, so it currently doesn't intend to log. This makes me
think that passing NULL for lxcpath is the right thing to do in
this patch. If you want me to make it so lxc-init can log, I can do
that but I think it should be in a different change :)

--

Signed-off-by: Dwight Engen <dwight.engen@oracle.com>
Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>