overlayRoot.sh

Squash File System over OverlayFS

Forked from: https://wiki.psuter.ch/doku.php?id=solve_raspbian_sd_card_corruption_issues_with_read-only_mounted_root_partition

Repository folder structure

/src
├── overlay
│   └── overlayRoot.sh                  # Original script v1.1 Created by Pascal Suter
│
└── overlay_sfs                         # Custom resources
    ├── boot                            # Contain boot files
    │   ├── cmdline-no_overlay.txt      # Boot Raspberry without OverlayFS
    │   └── cmdline-overlay.txt         # Boot Raspberry with OverlayFS
    └── sbin                            # Script to create OverlayFS and SquashFS
        └── overlayRoot.sh              # SquashFS over OverlayFS script v1.4

Installation

NOTE: This script has been tested with Raspbian OS (32-bit) Lite (Debian Buster)

1. First of all, create the folder structure:

   /lib/live/
   ├── mounted
   │   ├── ro          # Where Lower overlay folder is located
   │   ├── rw          # Where Upper and Work overlay folder is located
   │   └── squashed    # Where .sfs file is unsquashed
   └── squashfs        # Where .sfs file is located
   

   To do that:

   sudo -s
   mkdir /lib/live
   mkdir /lib/live/mounted
   mkdir /lib/live/mounted/ro
   mkdir /lib/live/mounted/rw
   mkdir /lib/live/mounted/squashed
   mkdir /lib/live/squahfs
   

2. Install Squasfs

   sudo apt-get install squashfs-tools -y 
   

3. Copy overlayRoot.sh script into /sbin/

   • I usually copy from my computer to Raspberry /home/user path using:

     # From computer terminal
     sudo scp -r /pc_overlayRoot rsp_user@rsp_ip_address:/destination_path
     

   • After copy the script, simply move to /sbin path runing:

     sudo mv /home/user/overlayRoot.sh /sbin/
     

   • Make it executable:

     chmod +x /sbin/overlayRoot.sh
     

4. Disable swap

   dphys-swapfile swapoff
   dphys-swapfile uninstall
   update-rc.d dphys-swapfile remove
   systemctl stop dphys-swapfile
   systemctl disable dphys-swapfile
   

5. Change your boot parameter in /boot/cmdline.txt. Adding init=/sbin/overlayRoot.sh:

   • cmdline.txt with OverlayFS

   console=serial0,115200 console=tty1 root=PARTUUID=97652995-02 rootfstype=ext4 elevator=deadline fsck.repair=yes rootwait init=/sbin/overlayRoot.sh
   

   • cmdline.txt without OverlayFS

   console=serial0,115200 console=tty1 root=PARTUUID=97652995-02 rootfstype=ext4 elevator=deadline fsck.repair=yes rootwait 
   

   NOTE: Can copy cmdline-overlay.txt and cmdline-no_overlay.txt from this repository and paste in your system

6. Reboot time }: )

   reboot 
   

Enable / Disable OverlayFS

Copy cmdline-no_overlay.txt and cmdline-overlay.txt into /boot/ path.

After runing the script /boot/ partition is mounted as a RW. To Enable or Disable OverlayFS:

• Enable OverlayFS:

  cp /boot/cmdline-overlay.txt /boot/cmdline.txt
  

• Disable OverlayFS:

  cp  /boot/cmdline-no_overlay.txt /boot/cmdline.txt
  

• After modify cmdline.txt file reboot Rapsberry sudo reboot

Create Squash file

For this example I've created a 3 test files which will be located in /home and /etc folders after mount OverlayFS.

1. Create a temp folder in /home/user (for exemple):

   sudo -s
   mkdir /home/user/squahsfs_tmp 
   

2. Inside the squash file we will add a file which will be located inside /etc/ and /home/ folders (just for testing), so we should create 2 new folders inside squashfs_tmp:

   cd /home/user/squahsfs_tmp
   mkdir etc
   mkdir home
   

3. Create some test files inside this folders:

   touch etc/hello_etc
   touch home/home_file_01
   touch home/home_file_01
   

4. We've implemented the changes so is time to create a SFS file:

   cd ..                                               # We're located in /home/user path right now
   squashfs squahsfs_tmp file_system.sfs -comp xz      # Creating SFS File }:)
   

   This command generate a sfs file call file_system.sfs based in squahfs_tmp folder content.
5. In the script the /lib/live/squahsfs directory is defined as the location where the file will be found the squash files so we should move the file.

   mv /home/user/squahsfs_tmp /lib/live/squashfs
   

6. Remove squasfs_tmp folder

   rm -rf /home/user/squashfs_tmp 
   

7. Enable overlay

   cp /boot/cmdline-overlay.txt /boot/cmdline.txt
   

8. Reboot time }: )

   reboot 
   

9. If everything has worked as we expected we will see:

   ls /home
    ├── home_file_01
    ├── home_file_02
    └── other /home files...
   
   ls /etc
    ├── hello_etc
    └── other /etc files...
   

Update Squash file

Update squashs file adding or removing some file. To do that:

1. Reboot system without OverlayFS

   sudo -s
   cp  /boot/cmdline-no_overlay.txt /boot/cmdline.txt
   reboot
   

2. Go to squashfs default path

   sudo -s
   cd /lib/live/squashfs
   

3. Unsquash file_system.sfs

   unsquashfs -f file_system.sfs
   

   After run this command a folder squashfs-root will appear.

   /lib/live/squashfs
     ├── file_sytem.sfs
     └── squashfs-root
   

4. Modify squashfs-root content removing home_file_02 (for exemple)

   rm -rf squashfs-root/home/home_file_02 
   

5. Remove old file_system.sfs

   rm -rf file_system.sfs
   

6. Create the new sfs file

   squashfs squashfs-root file_system.sfs -comp xz
   

7. Now modify cmdline.txt to mount overlayFS after reboot and apply the sfs changes

   cp /boot/cmdline-overlay.txt /boot/cmdline.txt
   

8. Rebot time }: )

   reboot 
   

The other way to modify squashfs:

1. Remount RO partition

   sudo -s
   mount -o remount,rw /lib/live/mounted/ro 
   

2. Go to squashfs folder

   cd /lib/live/mounted/ro/lib/live/squashfs
   

3. Repeat steps from 3 until 8 indicated in the previous section

Contact

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• Github. OxDAbit
• Mail. oxdabit@protonmail.com