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Pandu Poluan wrote, at 12/13/2011 10:26 PM: |
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> On Dec 14, 2011 1:06 AM, "Tanstaafl" <tanstaafl@×××××××××××.org |
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> <mailto:tanstaafl@×××××××××××.org>> wrote: |
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> > What should I set this to? Assuming that Linode is indeed using Xen, would |
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> it be: |
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> > rc_sys="xenU" |
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> > ? |
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> AFAIK Linode uses Xen so "xenU" is correct. |
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> What I really want to know is what happens if we specify a 'wrong' rc_sys value... |
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> (I also want to know why 'rc -S' is so unhelpful, but not as much as the above.) |
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i have looked through openrc sources and experimented a bit; the idea of rc_sys |
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is simple: the contents of that variable affects 'keyword' dependencies in |
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/etc/init.d/ scripts. the feature is documented, see runscript(8) for details, |
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but apparently does not work as expected. i also did not find valuable 'keyword' |
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dependencies in software packages i use thus considered that rc_sys might be set |
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to any value with no side effects |
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another thing i found is an $RC_SYS environment variable available to all |
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scripts initiated by rc; that one is set to value defined in /etc/rc.conf or |
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automatically detected if rc_sys is not explicitly set. the automatic detection |
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is trivial, eg. if the directory "/proc/xen" does exist, then $SYS_RC is set to |
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XENU. setting of $SYS_RC to XEN0 would be in case of "/proc/xen" existence and |
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if contents of the file /proc/xen/capabilities is equal to "control-d". all that |
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stuff could be found in src/librc/librc.c |
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i'm using $RC_SYS as a flag controlling start of xen dom0 daemons: rc_sys is |
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commented out in /etc/rc.conf to let runscript autodetect the environment. all |
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xen related stuff is started from /etc/local.d, like that: |
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$ cat /etc/local.d/xen.start |
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if [ "x$RC_SYS" = "xXEN0" ]; then |
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# start xenstored, xenconsole, configure xen networking etc |
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else |
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# do something else related to baremetal os boot |
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fi |
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this slightly speeds up boot process and produces more clear logs |