diff --git a/Devterm-CM3-ubuntu-server-image.md b/Devterm-CM3-ubuntu-server-image.md
index 2bf6106..f581679 100644
--- a/Devterm-CM3-ubuntu-server-image.md
+++ b/Devterm-CM3-ubuntu-server-image.md
@@ -1,5 +1,6 @@
 ubuntu-21.04-preinstalled-server-armhf+raspi.img
 
+### Prepare
 **/boot/cmdline.txt**  
 ```
 console=serial0,115200 console=tty1 root=PARTUUID=78e1086a-02  rootfstype=ext4 elevator=deadline rootwait fixrtc splash
@@ -11,7 +12,20 @@ PARTUUID=78e1086a-02   	   /         ext4   discard,errors=remount-ro       0 1
 PARTUUID=78e1086a-01       /boot/    vfat   defaults        0       1
 ```
 
+### Enter chroot
+sudo losetup -P /dev/loop10 ubuntu-21.04-preinstalled-server-armhf+raspi.img
+sudo mount /dev/loop10p2 /mnt/p2
+sudo mount /dev/loop10p1 /mnt/p2/boot
+cd /mnt/p2
+sudo mount --bind /dev dev/
+sudo mount --bind /sys sys/
+sudo mount --bind /proc proc/
+sudo mount --bind /dev/pts dev/pts
 
+sudo chroot .
+
+
+### Inside chroot
 ```
 sudo apt remove linux-image-raspi linux-image-5.11.0-1007-raspi -y
 sudo apt install net-tools network-manager -y
@@ -46,5 +60,7 @@ EOF'
 
 `sudo apt-get install tasksel`
 
+### Outside chroot
+
 `sudo tasksel` to select desktop env