How to --saveraw a specific volume?

[wattyka]

watz@antares:~/Downloads$ ubidump/ubidump.py --listfiles 2-rootfs1.bin
==> 2-rootfs1.bin <==
4 named volumes found, 5 physical volumes, blocksize=0x40000
== volume b'rootfs_ubifs' ==
volume contains a squashfs filesystem, extract with --saveraw, and then use unsquashfs
E: node magic num mismatch
== volume b'METADATA' ==
unknown magic: 1b000000
E: node magic num mismatch
== volume b'METADATACOPY' ==
unknown magic: 1b000000
E: node magic num mismatch
== volume b'filestruct_full_debug.bin' ==
unknown magic: ef1a0000
E: node magic num mismatch
watz@antares:~/Downloads$

Help says "--saveraw FILENAME save the entire volume to the specified file"

Which one of the volumes? How can I specify it?

Thanks!