adb shell mount
Mount new filesystem(s) on directories. With no arguments, display existing mounts.
mount [-afFrsvw] [-t TYPE] [-o OPTION,] [[DEVICE] DIR]
-a mount all entries in /etc/fstab (with -t, only entries of that TYPE)
-O only mount -a entries that have this option
-f fake it (don't actually mount)
-r read only (same as -o ro)
-w read/write (default, same as -o rw)
-t specify filesystem type
OPTIONS is a comma separated list of options, which can also be supplied as --longopts.
This mount autodetects loopback mounts (a file on a directory) and bind mounts (file on file, directory on directory), so you don't need to say --bind or --loop. You can also "mount -a /path" to mount everything in /etc/fstab under /path, even if it's noauto.