diff --git a/usr/share/rear/layout/save/default/31_autoexclude_usb.sh b/usr/share/rear/layout/save/default/31_autoexclude_usb.sh
index 6ee0e45..75b4080 100644
--- a/usr/share/rear/layout/save/default/31_autoexclude_usb.sh
+++ b/usr/share/rear/layout/save/default/31_autoexclude_usb.sh
@@ -36,7 +36,7 @@ do
 
     grep -q "^$REAL_USB_DEVICE " /proc/mounts
     if [[ $? -eq 0 ]]; then
-        local usb_mntpt=$(grep -P "^$REAL_USB_DEVICE\s" /proc/mounts | cut -d" " -f2 | tail -1)
+        local usb_mntpt=$(grep -E "^$REAL_USB_DEVICE\s" /proc/mounts | cut -d" " -f2 | tail -1)
         if ! IsInArray "$usb_mntpt" "${AUTOEXCLUDE_USB_PATH[@]}" ; then
             AUTOEXCLUDE_USB_PATH=( ${AUTOEXCLUDE_USB_PATH[@]} $usb_mntpt )
             Log "Auto-excluding USB path $usb_mntpt [device $REAL_USB_DEVICE]"
diff --git a/usr/share/rear/output/USB/Linux-i386/30_create_extlinux.sh b/usr/share/rear/output/USB/Linux-i386/30_create_extlinux.sh
index fdbb3e9..efdd558 100644
--- a/usr/share/rear/output/USB/Linux-i386/30_create_extlinux.sh
+++ b/usr/share/rear/output/USB/Linux-i386/30_create_extlinux.sh
@@ -3,7 +3,7 @@
 function get_usb_syslinux_version {
     for file in $BUILD_DIR/outputfs/{boot/syslinux,}/{ld,ext}linux.sys; do
         if [[ -s "$file" ]];  then
-            strings $file | grep -P -m1 "^(EXT|SYS)LINUX \\d+.\\d+" | cut -d' ' -f2
+            strings $file | grep -E -m1 "^(EXT|SYS)LINUX \\d+.\\d+" | cut -d' ' -f2
             return 0
         fi
     done
diff --git a/usr/share/rear/output/USB/Linux-i386/85_make_USB_bootable.sh b/usr/share/rear/output/USB/Linux-i386/85_make_USB_bootable.sh
index 49739d4..3cffc94 100644
--- a/usr/share/rear/output/USB/Linux-i386/85_make_USB_bootable.sh
+++ b/usr/share/rear/output/USB/Linux-i386/85_make_USB_bootable.sh
@@ -22,7 +22,7 @@ if [[ "$usb_syslinux_version" ]] && version_newer "$usb_syslinux_version" "$sysl
 fi
 
 # Make the USB bootable
-usb_filesystem=$(grep -P "^($USB_DEVICE|$REAL_USB_DEVICE)\\s" /proc/mounts | cut -d' ' -f3 | tail -1)
+usb_filesystem=$(grep -E "^($USB_DEVICE|$REAL_USB_DEVICE)\\s" /proc/mounts | cut -d' ' -f3 | tail -1)
 case "$usb_filesystem" in
 	(ext?)
 		if [[ "$FEATURE_SYSLINUX_EXTLINUX_INSTALL" ]]; then
diff --git a/usr/share/rear/prep/USB/Linux-i386/35_check_usb_disk.sh b/usr/share/rear/prep/USB/Linux-i386/35_check_usb_disk.sh
index 4d280c1..a166f94 100644
--- a/usr/share/rear/prep/USB/Linux-i386/35_check_usb_disk.sh
+++ b/usr/share/rear/prep/USB/Linux-i386/35_check_usb_disk.sh
@@ -9,7 +9,7 @@ REAL_USB_DEVICE=$(readlink -f $USB_DEVICE)
 StopIfError "USB device '$USB_DEVICE' is not a block device"
 
 ! grep -q "^$REAL_USB_DEVICE " /proc/mounts
-StopIfError "USB device '$USB_DEVICE' is already mounted on $(grep -P "^$REAL_USB_DEVICE\\s" /proc/mounts | cut -d' ' -f2 |tail -1)"
+StopIfError "USB device '$USB_DEVICE' is already mounted on $(grep -E "^$REAL_USB_DEVICE\\s" /proc/mounts | cut -d' ' -f2 |tail -1)"
 
 # We cannot use the layout dependency code in the backup phase (yet)
 #RAW_USB_DEVICE=$(find_disk $REAL_USB_DEVICE)