How to clone OS from SD to SSD using command line?

Question

I have set up my Raspberry Pi 4 for use as a small home server, running OpenMediaVault. Currently, the Pi is running from an SD card, but I'd like to switch to an SSD. I've found several tutorials explaining how to do this, but all of them use the SD Card Copier utility (available with the desktop version of Raspberry Pi OS) to clone the OS from the SD to the SSD. I need to use the Lite version of the OS that does not have a desktop. Is there a way to clone the SD to SSD using the command line, and then boot from the SSD? Can I use dd for this purpose?

I have no way to mount the SSD on my laptop (and would prefer not to buy an adapter just for this purpose), so I need to work from the Pi itself.

Answer 1

Have a look at rpi-clone. It's on GitHub. The author is Bill W(ilson?).

Answer 2

There is nothing magical about SD Card Copier - is just reads the SD Image, creates the appropriate partitions on the target then uses a file copy similar to rsync to copy contents.

I am sure you could do the same using dd although you would then be responsible for expanding the root partition.

I haven't done this, but do similar from SD Card to SD Card. This needs to be cognisant of PARTUUID which may need adjusting depending on how the partitions are created. Again I have scripts to change PARTUUID which is a good idea for clones (SD Card Copier has an option for this).

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NOTE that I wouldn't do this; I would backup to an image and burn to a SSD.

If you have an SSD you will need a USB adapter for the Pi, so you already have the hardware to mount on the laptop. However if you REALLY want to do this on the Pi read on:-

First attach your SSD (probably in /dev/sda) then use dd to copy /dev/mmcblk0 to the SSD.

Then use the following script on the SSD to check PARTUUID.

If this is OK you could then boot to the SSD, and use raspi-config to resize the root partition.

If not you will need to change to match your PARTUUID

#! /bin/bash
# 2020-03-09
# 2021-02-10
# Check consistency of Partition ID on mounted SD Card

BOOT_MOUNT='/mnt/SDA1'
ROOT_MOUNT='/mnt/SDA2'

# Check/create Mount Points
if [ ! -e $BOOT_MOUNT ]; then
    mkdir $BOOT_MOUNT
fi
if [ ! -e $ROOT_MOUNT ]; then
    mkdir $ROOT_MOUNT
fi
    echo "mounts " $BOOT_MOUNT  $ROOT_MOUNT
if [ -e /dev/sda ]; then
    SD1='/dev/sda1'
    SD2='/dev/sda2'
    SD='/dev/sda'
else
    SD1='/dev/sdb1'
    SD2='/dev/sdb2'
    SD='/dev/sdb'
fi
echo $SD

# Mount Partitions
if ! $(mountpoint -q $BOOT_MOUNT); then
    sudo mount $SD1 $BOOT_MOUNT # mount partition containing boot files
fi
if ! $(mountpoint -q $ROOT_MOUNT); then
    sudo mount $SD2 $ROOT_MOUNT # mount root partition containing OS files
fi


# Determine Disk identifier of SD Card
DISKID=$(sudo fdisk -l $SD | awk '/Disk identifier/ {print $3};' | sed 's/0x//')

# Use sed to delete all BEFORE PARTUUID= and all AFTER -0  in $BOOT_MOUNT/cmdline.txt
ROOTPART=$(sed -e 's/^.*PARTUUID=//' -e 's/-0.*$'// $BOOT_MOUNT/cmdline.txt)

echo -e "Disk ID\t\t"$DISKID
echo -e "root PARTUUID\t"$ROOTPART

# find first PARTUUID ext4 in $ROOT_MOUNT/etc/fstab
EXISTFSTABPART=$(awk '/PARTUUID.*ext4/ {print $1; exit};' $ROOT_MOUNT/etc/fstab | sed -e 's/^.*PARTUUID=//' -e 's/-0.*$'//)

echo -e "Existing fstab\t"$EXISTFSTABPART

if [ $DISKID = $EXISTFSTABPART ]; then
    echo "Looks OK!"
else
    echo "Partition ID mismatch!"
    # Edit cmdline.txt & fstab to new DISKID & create new temporary files
    sed -e "s/$ROOTPART/$DISKID/" $BOOT_MOUNT/cmdline.txt > cmdline.txt.new
    sed -e "s/$ROOTPART/$DISKID/" $ROOT_MOUNT/etc/fstab > fstab.new
    echo -n "Set DiskID to ${DISKID} on $SD (y/n)? "
    while read -r -n 1 -s answer; do
        if [[ "${answer}" = [yY] ]]; then
          echo "Change"
          sudo cp -v cmdline.txt.new $BOOT_MOUNT/cmdline.txt
          sudo cp -v fstab.new $ROOT_MOUNT/etc/fstab
          break
        else
          echo "Aborted"
          exit
        fi
    done
fi

Answer 3

You shouldn't make a backup of a "live" filesystem with dd - it has its uses, but backing up a "live" system is not one of them. It's been said of one who follows this practice: "If you're lucky, the filesystem corruption will be detected as soon as you try to mount the copy. If you're unlucky, it won't be detected until later."

I'll assume you know how to configure your RPi to boot from an external SSD, & won't cover that. But if you're unsure about this, read USB mass storage boot.

Cloning your existing microSD to a bootable SSD from the command line on a single RPi is a two-step process:

Step 1: Install image-utils & make an image file clone of your SD card. Start at the Show Me How heading of this post, or do something like this (Note: my exe copy of image-backup lives in ~/bin):

$ sudo /home/pi/bin/image-backup

Answer the questions when prompted. Creation of the image file required approx 2.5 minutes to complete on my system.

My image file was saved as:

/mnt/Passport2TB/img_backups/20210701_Pi4B_imagebackup.img
Yours will likely be different, but note its name and location as you'll need this in Step 2.

Step 2: We'll now use dd to copy the image file created in Step 1 to the SSD. This avoids issues with dd mentioned previously because neither the input file (if), nor the output file (of) are mounted/active.

Connect your SSD to one of the USB ports, then use lsblk to examine all block storage devices connected to your system. For example, here's mine:

$ lsblk --fs
NAME        FSTYPE LABEL       UUID                                 FSAVAIL FSUSE% MOUNTPOINT
sda
└─sda1      ext4   PASSPORT2TB 86645948-d127-4991-888c-a466b7722f05    1.5T    11% /mnt/Passport2TB
sdb
mmcblk0
├─mmcblk0p1 vfat               6969-16D1                             206.5M    19% /boot
└─mmcblk0p2 ext4               f6ea6ef9-68be-479d-b447-5f76391cc02f   22.7G    18% /

Note carefully:

1. sda1 is a mounted USB drive where I saved the image file created in Step 1. Confirm that this partition/device is mounted by reviewing the MOUNTPOINT column in the output.
2. sdb is the SSD on my system. Your SSD may be assigned a different device designation (sdc, sdf, etc). Confirm that your SSD drive (or sdb in this example) is not mounted by confirming there is nothing listed for it in the MOUNTPOINT column. If it is mounted, un-mount it using sudo umount /dev/sdb & verify this by re-running lsblk --fs.
3. mmcblk0 is your microSD card - the card you currently boot from. Of course it is mounted at two points: the root ext4 partition /, and the boot FAT partition /boot.

Once you're satisfied with your examination, you are ready to copy the image file created in Step 1 to the SSD:

$ sudo dd bs=4M status=progress if=/mnt/Passport2TB/img_backups/20210701_Pi4B_imagebackup.img of=/dev/sdb conv=fdatasync  

# sample output :
4383047680 bytes (4.4 GB, 4.1 GiB) copied, 160 s, 27.4 MB/s
1048+1 records in
1048+1 records out
4396003328 bytes (4.4 GB, 4.1 GiB) copied, 165.296 s, 26.6 MB/s

_{See man dd if you've any questions re the options.}

You may now remove your microSD card, and boot from your SSD.

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DEPRECATED If you had a 2nd system with a GUI, you might consider using rpi-imager in Step 2 - but think of all the fun? you'd be missing.

Step 2: Install rpi-imager on a desktop/laptop system & use it to "install" the image file you created in Step 1. Installation of rpi-imager on a Linux system using apt (e.g. Debian/Ubuntu) is as follows:

sudo apt-get update  
sudo apt-get full-upgrade   
sudo apt install rpi-imager

_{note that the update and upgrade steps should always be performed prior to installation of new packages.}