termrc: add unsupervised rescue shell on /dev/eia1

eia0 cannot be interrupted -- a plain uart turns DEL into a byte, not a
note -- so a command blocked on eia0 can only be killed from an
independent shell.  Both serial shells are deliberately not services:
they are the channel you need when the supervisor is what is broken, so
they start above svcinit and do not depend on it.

1 files changed, 10 insertions, 0 deletions

diff --git a/svc/termrc.work b/svc/termrc.work
index 9c12bf0..627c8b4 100755
--- a/svc/termrc.work
+++ b/svc/termrc.work
@@ -15,6 +15,16 @@ mount -qb /srv/cons /dev
 # serial shell for host-side control
 while(){ rc -i </dev/eia0 >/dev/eia0 >[2=1]; sleep 1 }&
 
+# rescue shell on the second uart.  eia0 cannot be interrupted: it is a plain
+# uart, not the console, so DEL over it is only a byte and the kernel never
+# turns it into a note.  A command blocked on eia0 can therefore be killed
+# only from an independent shell, which is this one.
+#
+# Both of these are deliberately NOT services.  They are the channel you need
+# when the supervisor is the thing that is broken, so they must not depend on
+# it -- note they start here, above svcinit.
+while(){ rc -i </dev/eia1 >/dev/eia1 >[2=1]; sleep 1 }&
+
 # mount points (if not done by bootrc already)
 >[2]/dev/null {
 mntgen -s slashn /n && chmod 666 /srv/slashn