diff -up os-prober-1.57/common.sh.logger-factor-out os-prober-1.57/common.sh
--- os-prober-1.57/common.sh.logger-factor-out	2013-02-05 21:19:38.896088800 +0330
+++ os-prober-1.57/common.sh	2013-02-05 21:20:04.624767147 +0330
@@ -62,10 +62,14 @@ cache_progname() {
   esac
 }
 
-log() {
-  cache_progname
-  logger -t "$progname" "$@"
-}
+# fd_logger: bind value now, possibly after assigning default. 
+eval '
+  log() {
+    cache_progname
+    echo "$progname: $@"  1>&'${fd_logger:=9}'
+  }
+'
+export fd_logger  # so subshells inherit current value by default
 
 error() {
   log "error: $@"
@@ -81,10 +85,14 @@ debug() {
   fi
 }
 
-result () {
-  log "result:" "$@"
-  echo "$@"
-}
+# fd_result: bind value now, possibly after assigning default.
+eval '
+  result() {
+    log "result:" "$@"
+    echo "$@"  1>&'${fd_result:=1}'
+  }
+'
+export fd_result  # so subshells inherit current value by default
 
 # shim to make it easier to use os-prober outside d-i
 if ! type mapdevfs >/dev/null 2>&1; then
diff -up os-prober-1.57/linux-boot-prober.logger-factor-out os-prober-1.57/linux-boot-prober
--- os-prober-1.57/linux-boot-prober.logger-factor-out	2013-02-05 21:19:59.395832518 +0330
+++ os-prober-1.57/linux-boot-prober	2013-02-05 21:24:42.301295713 +0330
@@ -1,4 +1,12 @@
 #!/bin/sh
+
+# dash shell does not have "{varname}>&1" feature that bash shell has
+# for auto-assignment of new filedescriptors.
+# It is cumbersome to write the 'eval' to use our own variables in redirections.
+# Therefore use fixed numbers.
+export fd_result=3  # file descriptor for external results
+export fd_logger=9  # file descriptor for input to logger
+
 . /usr/share/os-prober/common.sh
 
 set -e
@@ -147,6 +155,7 @@ if ! mapped="$(mapdevfs "$partition")";
 	continue
 fi
 
+( (
 if ! grep -q "^$mapped " "$OS_PROBER_TMP/mounted-map"; then
 	for test in /usr/lib/linux-boot-probes/*; do
 		if [ -x $test ] && [ -f $test ]; then
@@ -186,3 +195,5 @@ else
 		fi
 	fi
 fi
+) 9>&1 | logger 1>&-  # fd_logger
+) 3>&1  # fd_result
diff -up os-prober-1.57/os-prober.logger-factor-out os-prober-1.57/os-prober
--- os-prober-1.57/os-prober.logger-factor-out	2013-02-05 21:19:52.914913541 +0330
+++ os-prober-1.57/os-prober	2013-02-05 21:25:35.168634780 +0330
@@ -1,7 +1,14 @@
 #!/bin/sh
 set -e
 
-. /usr/share/os-prober/common.sh
+# dash shell does not have "{varname}>&1" feature that bash shell has
+# for auto-assignment of new filedescriptors.
+# It is cumbersome to write the 'eval' to use our own variables in redirections.
+# Therefore use fixed numbers.
+export fd_result=3  # file descriptor for external results
+export fd_logger=9  # file descriptor for input to logger
+
+ . /usr/share/os-prober/common.sh
 
 newns "$@"
 require_tmpdir
@@ -129,6 +136,7 @@ fi
 
 : >"$OS_PROBER_TMP/btrfs-vols"
 
+( (
 for partition in $(partitions); do
 	if ! mapped="$(mapdevfs "$partition")"; then
 		log "Device '$partition' does not exist; skipping"
@@ -193,3 +201,5 @@ for partition in $(partitions); do
 		fi
 	fi
 done
+) 9>&1 | logger 1>&-  # fd_logger
+) 3>&1  # fd_result