diff --git a/installer/installer.sh b/installer/installer.sh
index 3a469ad..b1984db 100755
--- a/installer/installer.sh
+++ b/installer/installer.sh
@@ -15,6 +15,16 @@ MAMBAWELCOME_SCRIPT=/usr/share/openmamba/mambawelcome/mambawelcome.sh
 LOG_FILE=/var/log/install-$INSTALL_DATE.log
 MOUNTPOINT=/mnt/install
 KERNEL_RELEASE=`uname -r`
+PIDFILE=/run/openmamba-installer.pid
+
+[ -e $PIDFILE ] && PIDCHECK=`cat $PIDFILE`
+
+[ "$PIDCHECK" -a -e /proc/$PIDCHECK ] && {
+   echo "Error: an installer process is already running; exiting."
+   exit 0
+}
+
+trap "umount -R $MOUNTPOINT 2>/dev/null; rm -f $PIDFILE" 0 HUP INT QUIT ABRT KILL TERM
 
 function abort() {
    [ "$DCOPID" ] && {
@@ -22,6 +32,7 @@ function abort() {
       dcop $DCOPID KommanderIf setText finallabel $"Installation aborted :-("
       dcop $DCOPID KommanderIf setEnabled next true
    }
+   rm -f $PIDFILE
    exit 1
 }
 
@@ -34,6 +45,7 @@ function finished() {
       dcop $DCOPID KommanderIf setEnabled next true
       dcop $DCOPID KommanderIf setEnabled ProgressGroupBox true
    }
+   rm -f $PIDFILE
    exit 1
 }
 
@@ -96,6 +108,8 @@ function get_udisks_key() {
    exit 0
 }
 
+echo $$ > $PIDFILE
+
 DCOPID=$2
 
 echo $"\
@@ -333,7 +347,8 @@ done
 for d in etc bin boot lib lib64 opt sbin srv usr var root; do
    [ "$INSTALL_CLONE_MODE" != "1" ] && canonical_dir=/squashfs/$d || canonical_dir=`readlink -f /$d`
    [ -e $canonical_dir ] || continue
-   cp -av $canonical_dir $MOUNTPOINT/ | cp_parser || {
+   cp -av $canonical_dir $MOUNTPOINT/ | cp_parser
+   [ ${PIPESTATUS[0]} -eq 0 ] || {
       echo $"Error: cannot copy $canonical_dir to $MOUNTPOINT; aborting." >&2
       abort
    }
@@ -640,4 +655,5 @@ finished
 
 echo $"Installation done. You can now reboot to start the freshly installed system."
 
+rm -f $PIDFILE
 exit 0