I try to make my rootfs read-only. I thought that I better use overlay filesystem for this purpose (I don't have other alternatives now).
Yet, after many trials and changing fstab, I can't manage to find any fstab which manage to start ubuntu with rootfs as readonly. I also googled itm but found no examples. This is what I tried, and I also tried many variations (options column), but still get error in overlay mount.
As you can see, the main changes are adding "ro" to the rootfs, and adding overlay for /etc /var and /home.
# /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> # / was on /dev/sda1 during installation UUID=075d905c-5c56-4eae-9402-5a880d108a8c / ext4 ro,errors=remount-ro 0 1 /dev/sdb /media/store ext4 defaults 1 1 # swap was on /dev/sda5 during installation UUID=e190d8d1-5490-4ef5-9547-a38aefa44b3e none swap sw 0 0 /root/myswapfile swap swap defaults 0 0 overlay /var overlay rw,noatime,lowerdir=/var,upperdir=/media/store /1,workdir=/media/store /11 0 2 overlay /etc overlay rw,noatime,lowerdir=/etc,upperdir=/media/store /2,workdir=/media/store /22 0 2 overlay /home overlay rw,noatime,lowerdir=/home,upperdir=/media/store /3,workdir=/media/store /33 0 2
Overlay is supported in my kernel, and things does works if I change my rootfs option in ftab from ro to writebale, but I need it read-only!
Thanks for any idea,