fuse-ods2

Read-only FUSE driver for ODS-2 (Files-11 On-Disk Structure Level 2), the native filesystem of OpenVMS.

fuse-ods2 lets you mount raw disk dumps of ODS-2 volumes on Linux (and, best-effort, on macOS via macFUSE) so you can browse and copy files with ordinary tools (ls, cat, cp, find, ...) without booting an emulator or running an interactive ODS-2 utility.

Status

Early development. See TODO.md for the roadmap.

Building

Linux (Debian / Ubuntu)

sudo apt install libfuse3-dev pkg-config build-essential
make

CI builds on debian:stable. Fedora / Arch users want fuse3-devel / fuse3 instead.

macOS (best-effort)

brew install --cask macfuse
brew install pkg-config
make

The Makefile detects Darwin and resolves pkg-config fuse3 if macFUSE exposes that name, or falls back to pkg-config fuse.

Caveats on macOS:

• macFUSE installs a kernel extension that requires user approval in System Settings -> Privacy & Security the first time it loads.
• File ownership: macFUSE refuses to expose a mount to anyone other than the mounter unless you pass -o allow_other (and macFUSE has it enabled).
• Linux remains the primary tested platform; the upstream ods2 build used by the smoke test is not exercised in CI on macOS.

Usage

fuse-ods2 [options] <image> <mountpoint>

Mount a raw image read-only:

mkdir /tmp/m
fuse-ods2 vms-disk.dsk /tmp/m
ls /tmp/m
fusermount3 -u /tmp/m

Options

Option	Effect
-o offset=N	Skip N bytes at the start of the image (e.g. an MBR prefix)
-o vol=A,B,...	Volume set: extra image files for RVNs 2..N
-o allversions	Show every file version as NAME.EXT;n (default: latest only)
-o lower	Lowercase file names (default: uppercase, as on disk)
-o textmode	Strip RMS record headers from VAR/VFC files and convert to LF
-o uid=N/gid=N	Force a specific uid/gid on every file
-o debug	Verbose diagnostics on stderr
-s	Single-threaded (recommended at this stage)

The filesystem is always mounted read-only at the operation layer: every mknod / mkdir / unlink / write / chmod / setxattr / fallocate / ... returns EROFS. If you also want the kernel-level ro flag (so even root sees Read-only file system), pass -o ro on the command line.

statfs reports the volume's total block count derived from the home-block cluster size and image size. Free-block accounting needs the storage bitmap (a write-side concern) and is reported as zero.

catvms — decoding extracted record files

VMS text files are usually stored as RMS records, not as a flat byte stream. fuse-ods2 -o textmode decodes them on the fly while the volume is mounted, but if you have already copied a file out in raw mode (the default), catvms does the same job offline:

catvms file.txt              # autodetect, falls back to VAR
catvms --var      < f.txt    # force VAR (length-prefixed records)
catvms --vfc=2    f.lis      # VFC, 2-byte fixed control header
catvms --fix=80   card.dat   # FIX records, 80 bytes each
catvms --stmlf    f.txt      # already a stream, pass through
catvms --stmcr    f.mac      # CR-delimited stream, translate to LF
catvms --no-lf    --var f    # do not append LF after each record

catvms has no library dependencies; build it via make (or make catvms) along with fuse-ods2.

Project layout

src/        Wrapper code: FUSE operations, path lookup, I/O backend
ods2lib/    ODS-2 read-only core (extracted subset of the open-simh
            "ods2" utility, unmodified, original notices preserved)
test/       Test image generators and smoke scripts
build/      Object files (created by make)

Limitations

• Read-only.
• Indexed RMS files are exposed as raw bytes (no record-level access).
• ACLs and VMS-specific protection bits are mapped down to POSIX rwx bits, dropping the delete bit (which has no POSIX equivalent).
• ODS-5 volumes are not supported.
• VHD container images are not supported (raw images only).

License

MIT, see LICENSE.

The contents of ods2lib/ are derivative work from the open-simh simtools/extracters/ods2 package and retain the original authors' notices and license terms.