An example for using rsync to clone a linux system.

setup.sh

#!/bin/bash

### Colors
RED='\e[31m'
RED_B='\e[1;37;41m'
GREEN='\e[32m'
GREEN_B='\e[1;37;42m'
YELLOW_B='\e[1;43m'
NC='\e[0m'

### Tools
blkid=/sbin/blkid
sfdisk=/sbin/sfdisk

### Function for Triming Characters
trim_spaces() {
    echo -n $1 | sed -e "s/^[[:space:]]*//" -e "s/[[:space:]]*$//"
}

trim_tailing_slashes() {
    echo -n $1 | sed -e "s/[\/]*$//"
}

### Functions for result checking
check() {
    if [ $1 -eq 0 ]; then
        echo -e "${GREEN}Success${NC}"
    else
        echo -e "${RED}Failed${NC}"; exit 1
    fi
}

check_without_exit() {
    if [ $1 -eq 0 ]; then
        echo -e "${GREEN}Success${NC}"
    else
        echo -e "${RED}Failed${NC}"
    fi
}

check_empty() {
    if [ -z $2 ]; then
        echo -e "${RED_B}Error:${NC} $1 must not be empty"; exit 1
    fi
}

check_ip() {
    local  ip=$1
    local  stat=1

    if [[ $ip =~ ^[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}$  ]]; then
        OIFS=$IFS
        IFS='.'
        ip=($ip)
        IFS=$OIFS
        [[ ${ip[0]} -le 255 && ${ip[1]} -le 255 \
            && ${ip[2]} -le 255 && ${ip[3]} -le 255 ]]
        stat=$?
    fi
    if [ $stat -ne 0 ]; then
        echo -e "${RED_B}Error:${NC} $ip is not a volid ip address"; exit 1
    fi
}

### Get partition's UUID
get_blkid() {
    $blkid $1 | cut -f 2 -d " " | cut -f 2 -d "=" | sed -e 's/^"*//' -e 's/"*$//'
}

### Get block device from user
read -p 'Disk you want to use: ' Disk
Disk=$( trim_spaces $Disk  )
check_empty 'block device' $Disk
if [ ! -b $Disk ]; then
    echo -e "${RED_B}Error:${NC} $Disk is not a block device."; exit 1
fi
echo -en "Use ${GREEN_B}${Disk}${NC} as the target device!"
read -p ' Continue? (Y/n): ' Confirm
if [ "$Confirm" != 'Y' ]; then
    echo "Canceled by user!"; exit 0
fi

### Partition the disk
echo -e "${YELLOW_B}                 ${NC}"
echo -e "${YELLOW_B} -> Partition <- ${NC}"
echo -e "${YELLOW_B}                 ${NC}"
echo -n 'Destroy old partition table... '
dd if=/dev/zero of=$Disk bs=1024 count=1 &> /dev/null
check $?
echo -n 'Create new partition table... '
$sfdisk --force $Disk &> /dev/null << EOF
1M,4G,S,
,,L,*
EOF
check $?
echo -en "Format new partition ${GREEN_B}${Disk}1${NC} to swap... "
mkswap ${Disk}1 &> /dev/null
check $?
echo -en "Format new partition ${GREEN_B}${Disk}2${NC} to ext4... "
mkfs.ext4 ${Disk}2 &> /dev/null
check $?

### Sync system files from source
echo -e "${YELLOW_B}                       ${NC}"
echo -e "${YELLOW_B} -> Synchronization <- ${NC}"
echo -e "${YELLOW_B}                       ${NC}"
read -p 'Source host IP: ' rsync_ip
rsync_ip=$( trim_spaces $rsync_ip  )
check_ip $rsync_ip
read -p "Which section to use in source host(default 'all'): " rsync_section
rsync_section=$( trim_spaces $rsync_section  )
if [ -z $rsync_section ]; then
    rsync_section='all'
fi
read -p "Which dir to sync in source host(default '/mnt/debian_10'): " rsync_dir
rsync_dir=$( trim_spaces $rsync_dir  )
if [ -z $rsync_dir ]; then
    rsync_dir='/mnt/debian_10/'
else
    if [ $rsync_dir != "/"  ]; then
        rsync_dir=$( trim_tailing_slashes $rsync_dir  )
        rsync_dir=${rsync_dir}/
    fi
fi
echo -n 'Check connectivity... '
ping -c 1 $rsync_ip &> /dev/null
check $?
rsync_mount='/mnt/rsync_tmp'
echo -n "Mount ${Disk}2 to ${rsync_mount}... "
mkdir -p $rsync_mount &> /dev/null
mount ${Disk}2 $rsync_mount &> /dev/null
check $?
echo -n "Sync from ${rsync_ip}:${rsync_section}:${rsync_dir} ... "
rsync -avHX ${rsync_ip}::${rsync_section}${rsync_dir} ${rsync_mount}/ \
 --exclude={/dev/*,/proc/*,/sys/*,/tmp/*,/run/*,/mnt/*,/media/*,/lost+found} \
 &> /dev/null
check $?

### Create /etc/fstab
echo -e "${YELLOW_B}                    ${NC}"
echo -e "${YELLOW_B} -> Rebuild GRUB <- ${NC}"
echo -e "${YELLOW_B}                    ${NC}"
echo -n 'Generate /etc/fstab... '
cat << EOF > /tmp/fstab
# /etc/fstab: static file system information.
#
# Use 'blkid' to print the universally unique identifier for a
# device; this may be used with UUID= as a more robust way to name devices
# that works even if disks are added and removed. See fstab(5).
#
# <file system> <mount point>   <type>  <options>       <dump>  <pass>
UUID=$( get_blkid ${Disk}2  ) /               ext4    errors=remount-ro 0       1
UUID=$( get_blkid ${Disk}1  ) none            swap    sw                0       0
EOF
check $?
cp -v /tmp/fstab ${rsync_mount}/etc/fstab

### Create shell script for updating grub
echo -n 'Generate update_grub.sh... '
cat << EOF > /tmp/update_grub.sh
#!/bin/bash

grub-install ${Disk}
update-grub
EOF
chmod +x /tmp/update_grub.sh
check $?
cp -v /tmp/update_grub.sh ${rsync_mount}/tmp/update_grub.sh

### Reinstall GRUB
echo -n 'Reinstall GRUB... '
mount --bind /proc ${rsync_mount}/proc
mount --bind /sys  ${rsync_mount}/sys
mount --bind /dev  ${rsync_mount}/dev
mount --bind /run  ${rsync_mount}/run
chroot ${rsync_mount} /tmp/update_grub.sh &> /dev/null
check $?
echo -e "${GREEN_B}                        ${NC}"
echo -e "${GREEN_B} -> Install Success! <- ${NC}"
echo -e "${GREEN_B}                        ${NC}"

### Script end
read -p ' Reboot Now? (Y/n): ' reboot
if [ "$reboot" = 'Y' ]; then
    reboot
fi