Re: [gentoo-user] Two issues with OpenRC/baselayout2 migration on a hosted VM

[victor romanchuk <rom@persimplex.net>]

Pandu Poluan wrote, at 12/13/2011 10:26 PM:
>
>
> On Dec 14, 2011 1:06 AM, "Tanstaafl" <tanstaafl@libertytrek.org
> <mailto:tanstaafl@libertytrek.org>> wrote:
> >
> > What should I set this to? Assuming that Linode is indeed using Xen, would
> it be:
> >
> > rc_sys="xenU"
> >
> > ?
>
> AFAIK Linode uses Xen so "xenU" is correct.
>
> What I really want to know is what happens if we specify a 'wrong' rc_sys value...
>
> (I also want to know why 'rc -S' is so unhelpful, but not as much as the above.)
>

i have looked through openrc sources and experimented a bit; the idea of rc_sys
is simple: the contents of that variable affects 'keyword' dependencies in
/etc/init.d/ scripts. the feature is documented, see runscript(8) for details,
but apparently does not work as expected. i also did not find valuable 'keyword'
dependencies in software packages i use thus considered that rc_sys might be set
to any value with no side effects

another thing i found is an $RC_SYS environment variable available to all
scripts initiated by rc; that one is set to value defined in /etc/rc.conf or
automatically detected if rc_sys is not explicitly set. the automatic detection
is trivial, eg. if the directory "/proc/xen" does exist, then $SYS_RC is set to
XENU. setting of $SYS_RC to XEN0 would be in case of "/proc/xen" existence and
if contents of the file /proc/xen/capabilities is equal to "control-d". all that
stuff could be found in src/librc/librc.c

i'm using $RC_SYS as a flag controlling start of xen dom0 daemons: rc_sys is
commented out in /etc/rc.conf to let runscript autodetect the environment. all
xen related stuff is started from /etc/local.d, like that:

$ cat /etc/local.d/xen.start
if [ "x$RC_SYS" = "xXEN0" ]; then
# start xenstored, xenconsole, configure xen networking etc
else
# do something else related to baremetal os boot
fi

this slightly speeds up boot process and produces more clear logs