mount --bind /vital_data /untrusted_container/vital_data
mount -o remount,ro /untrusted_container/vital_data

mount --bind /src /dst

mount -o remount,ro /dst

mount -o remount,ro,bind /dst

mount --bind --make-rprivate /sbin/ $prefix/sbin/
mount -o remount,ro,bind $prefix/sbin/

mount --make-shared mountpoint
     mount --make-slave mountpoint
     mount --make-private mountpoint
     mount --make-unbindable mountpoint

mount --make-rshared mountpoint
     mount --make-rslave mountpoint
     mount --make-rprivate mountpoint
     mount --make-runbindable mountpoint