BeFS BeOS uses its own journaling filesystem, known as BeFS. A read-only Linux driver for this filesystem
FFS/UFS The Fast Filesystem (FFS; aka Unix Filesystem or UFS) was developed early in the history of Unix. It’s still used by many Unix and derivative systems, including FreeBSD and Solaris. In principle, FFS/UFS could have been adopted as a native Linux filesystem, but Linux’s write support for this filesystem is still considered dangerous
UDF The Universal Disk Format (UDF) is a filesystem designed for recordable CD, DVD, and recordable DVD media. Linux includes UDF support in the 2.4.x kernel series, but the write support is marked ”dangerous” and is very limited in terms of supported hardware.