Convert fstab device names to PARTUUID option. README changes.

Added --convert-fstab-to-partuuid option that converts a device name
using fstab and cmdline.txt to use PARTUUID as is standard in recent
Raspbian distributions.  Just a helper option for users that want to
convert.

Added back in clone to smaller 4GB card example.

Author: billw2

README.md

@@ -19,7 +19,7 @@ grub can be configured for this to be an officially  supported way of
 using rpi-clone.
 
 #### Clone by initialization
-Source disk mounted partition file system types are compared to
+Source disk mounted partition types are compared to
 corresponding destination disk partitions.
 If the types are not compatible, then the clone is an
 initialization.  First, the destination partition structure is
@@ -111,6 +111,7 @@ usage: rpi-clone sdN {-v|--verbose} {-f|--force-initialize}
          {-s|--setup} {-e|--edit-fstab sdX }
          {-m|--mountdir dir } {-l|--leave-sd-usb-boot}
          {-a|--all-sync} {-F|--Force-sync} {-x} {-V|--version}
+         {--convert-fstab-to-partuuid}
 
     -v      - verbose rsync, list all files as they are copied.
     -f      - force initialize the destination disk by imaging the booted disk.
@@ -140,6 +141,25 @@ usage: rpi-clone sdN {-v|--verbose} {-f|--force-initialize}
   -s option that has different meaning.
 
 ## rpi-clone Example Runs
+#### An aside note
+You will see in one example below that the clone command will need
+to be run differently depending on if device names or PARTUUID is used
+in /etc/fstab.  If device names are used you will have to add a "-e sdX"
+where sdX will be the "expected" disk name a USB disk is assigned during
+boot.  Usually this works, but if you have multiple disk devices plugged
+into USB ports it may not work.  While this may not be an issue for you now,
+recent Raspbian releases now use PARTUUID as standard and in the long
+run you may at some point want to convert.
+So as a convenience, if you want to convert to using
+PARTUUID, rpi-clone can do that for you, run:
+```
+$ sudo rpi-clone --convert-fstab-to-partuuid
+```
+You only need to ever do this once.  Subsequent rpi-clone runs will propagate
+PARTUUID usage to disks that you clone to.  This also converts cmdline.txt.
+But get some clone backups before doing this because this changes
+your booted disk.
+
 #### 1) First clone to a new SD card in USB card reader
 In this example a new SD card in a USB card reader has been plugged in
 that I want to clone to.  It shows up as sdb because I have another USB
@@ -313,7 +333,44 @@ likely has the SD card /boot partition mounted, the SD card is in use
 and using rpi-clone for a clone back to the SD card slot will not work.
 
 
-#### 6) Creating a Pi3 bootable USB hard drive with extra partitions
+#### 6) Clone to smaller 4GB SD card
+I happen to have an old 4GB SD card and here's a try to clone to it: 
+```
+root@rpi2: ~$ rpi-clone sda
+
+Booted disk: mmcblk0 15.8GB                Destination disk: sda 4.0GB
+---------------------------------------------------------------------------
+Part      Size    FS     Label           Part   Size    FS     Label
+1 /boot   58.4MB  fat16  --              1      58.4MB  fat16  --
+2 root    15.8GB  ext4   SD-RPI-16N      2       3.9GB  ext4   --
+---------------------------------------------------------------------------
+== SYNC mmcblk0 file systems to sda ==
+/boot       (22.5MB used)    : SYNC to sda1 (58.4MB size)
+/           (5.9GB used)     : SYNC to sda2 (3.9GB size)
+---------------------------------------------------------------------------
+Run setup script       : no
+Verbose mode           : no
+-----------------------:
+** FATAL **            : Partition 2: source used > destination space.
+-----------------------:
+
+Aborting!
+  Use -F to override used > space fail.
+
+```
+So even if rpi-clone thinks that the sync won't work because of lack of
+space, there is a -F option which will allow the clone to proceed
+anyway.  The interesting thing about this case is that while this might
+seem a bad idea, the sync will actually come close to succeeding.  That's
+because the root used space includes a 1.8GB file system based
+swap file (/var/swap) that will be excluded from the sync.  If this
+clone is forced with -F, the card may boot, but there could be some missing
+files if the rsync runs out of space and fails to complete and some things
+would not work.
+This is just a FYI.
+
+
+#### 7) Creating a Pi3 bootable USB hard drive with extra partitions
 I wanted to have a Pi3 hard drive USB boot with extra data partitions
 and I want to be able to clone back to 2 partition SD cards for use
 in other SD card booted Pis.  So when I initially clone to the hard drive
@@ -370,10 +427,10 @@ and powered back on into a hard drive boot.  I had previously boot
 enabled the Pi3.
 
 ## Cloning from a USB booted Pi with extra partitions
-Now I have booted the USB hard drive I cloned to in example 6 and will
+Now I have booted the USB hard drive I cloned to in example 7 and will
 try a few clones.
 
-#### 7) USB disk routine clone to 16GB SD card
+#### 8) USB disk routine clone to 16GB SD card
 For this case I haven't mounted any of the extra partitions and
 the Pi has only the /boot partition mounted.  The kernel has seen my hard
 drive as sdb but I'm using PARTUUID in fstab so there's no problem.
@@ -402,7 +459,7 @@ Verbose mode           : no
 Ok to proceed with the clone?  (yes/no): 
 ```
 
-#### 8) USB disk with mounted partition 5 clone to 16GB SD card
+#### 9) USB disk with mounted partition 5 clone to 16GB SD card
 Now I try the clone with one of my extra partitions mounted:
 ```
 pi@rpi0: ~$ sudo  rpi-clone sda
@@ -426,7 +483,7 @@ rpi-clone sees the mounted partition 5 and wants to clone it but finds
 there's not enough space on the destination disk and won't let me.
 A bigger disk is needed to clone all the way through partition 5.
 
-#### 9) USB disk with mounted partition 5 clone to 16GB SD card try 2
+#### 10) USB disk with mounted partition 5 clone to 16GB SD card try 2
 I've got things I'm working on and don't want to unmount the partition
 to make the clone work, so I use the -m option to tell rpi-clone to
 only clone root and /boot and exclude any other directory mounts not given

rpi-clone

@@ -1,6 +1,6 @@
 #!/bin/bash
 
-version=2.0.2
+version=2.0.4
 
 PGM=`basename $0`
 setup_command="$PGM-setup"
@@ -70,6 +70,7 @@ usage: $PGM sdN {-v|--verbose} {-f|--force-initialize}
          {-s|--setup} {-e|--edit-fstab sdX }
          {-m|--mountdir dir } {-l|--leave-sd-usb-boot}
          {-a|--all-sync} {-F|--Force-sync} {-x} {-V|--version}
+         {--convert-fstab-to-partuuid}
 
     -v      - verbose rsync, list all files as they are copied.
     -f      - force initialize the destination disk by imaging the booted disk.
@@ -113,7 +114,6 @@ usage: $PGM sdN {-v|--verbose} {-f|--force-initialize}
   Download:
     git clone https://github.com/billw2/rpi-clone
 "
-
 	exit 1
 	}
 
@@ -614,6 +614,7 @@ Unattended=0
 quiet=0
 custom_sync=0
 leave_sd_usb_boot=0
+convert_to_partuuid=0
 
 while [ "$1" ]
 do
@@ -688,6 +689,9 @@ do
 		-F|--Force-sync)
 			force_sync=1
 			;;
+		--convert-fstab-to-partuuid)
+			convert_to_partuuid=1
+			;;
 		-V|--version)
 			echo $PGM Version: $version
 			exit 0
@@ -734,6 +738,57 @@ then
     exit 1
 fi
 
+if ((convert_to_partuuid))
+then
+	unattended=0
+	Unattended=0
+
+	fstab=/etc/fstab
+	fstab_tmp=/tmp/fstab
+	fstab_save=${fstab}.${PGM}-save
+	confirm "This will change your $fstab, are you sure?" "abort"
+
+	cp $fstab $fstab_tmp
+	printf "\nConverting $fstab from device names to PARTUUID\n"
+	count=0
+	for ((p = 1; p <= n_src_parts; p++))
+	do
+		if grep -q "^/dev/${src_partition[p]}" $fstab_tmp
+		then
+			partuuid=$(lsblk -n -o PARTUUID /dev/${src_partition[p]})
+			sed -i "s/\/dev\/${src_partition[p]}/$partuuid/" $fstab_tmp
+			printf "  Editing $fstab, changing /dev/${src_partition[p]} to $partuuid\n"
+			((++count))
+		fi
+	done
+	if ((count))
+	then
+		cp $fstab $fstab_save
+		cp $fstab_tmp $fstab
+		printf "Your original fstab is backed up to $fstab_save\n"
+
+		cmdline_txt=/boot/cmdline.txt
+		cmdline_save=$cmdline_txt.${PGM}-save
+		if [ -f $cmdline_txt ] && grep -q "$src_root_dev" $cmdline_txt
+		then
+			root_part=${src_partition[root_part_num]}
+			partuuid=$(lsblk -n -o PARTUUID $src_root_dev)
+			if [ "$partuuid" != "" ]
+			then
+				cp $cmdline_txt $cmdline_save
+				sed -i "s/\/dev\/$root_part/PARTUUID=$partuuid/" $cmdline_txt
+				printf "  Editing $cmdline_txt, changing root=$src_root_dev to root=PARTUUID=$partuuid\n"
+				printf "Your original cmdline.txt is backed up to $cmdline_save\n"
+			fi
+		fi
+	else
+		printf "Could not find any $src_disk partition names in $fstab, nothing changed.\n"
+	fi
+	rm $fstab_tmp
+	echo ""
+	exit 0
+fi
+
 # dst_mount_flag enumerations:
 live=1
 temp=2
@@ -1031,10 +1086,12 @@ The destination disk is too small.
 					"Destination last partition resize to $space_readable"
 		printf "%-22s : %s\n" "" \
 					"  is too small to hold source used $used_readable."
-		if [ "$n_src_parts" == "$root_part_num" ]
+		if [ "$n_src_parts" == "$root_part_num" ] && ((!force_sync))
 		then
 			printf "%-22s : %s\n" "" \
 					"  This is the root partition, so aborting!"
+			printf "%-22s : %s\n" "" \
+					"  Use -F to override."
 			abort=1
 		elif ((!force_sync))
 		then