CAT filesystem

Shows a list of files as one big file. It is equal to output of cat command, hence the name.

Differs from a similar-named project in that it is optimised for working with a big list of files.

Primary purpose is to make par work with many files at once (by making par think that it's only one file).

Compile

• To compile on Ubuntu 16.04, install these packages:

    sudo apt install libfuse-dev make gcc pkgconf
  

• After that, follow usual way:

    make
  

Usage

• To generate a list of files:

    find . -type f -printf "%s %P\n" >{list file}
  

• To mount, from the same directory:

    ./catfs -s {list file} {mount point}
  

  You will see {mount point}/archive.cat file. It should be identical to the one produced by this command:

    find . -type f -print0 | xargs -0 cat >{reference file}
  

• To unmount:

    fusermount -u {mount point}
  

• To extract files if you have {list file} and archive.cat (copied from {mount point}):

    ./uncat {list file} archive.cat [filename]
  

  optionally passing name of the file to be extracted

Example with par2

Say, you have a directory with a lot of files in it. So many that par2 can't deal with all of them at once (it has a limit of 32k files). To work around this limitation, you can either use tar and create a single file with a copy of all your files in it, or:

cd backup/
find . -type f -printf "%s %P\n" >cat.fs
mkdir mount && ~/catfs -s cat.fs mount
par2create -r1 -n1 par2 mount/archive.cat
fusermount -u mount && rmdir mount

i.e.:

• go to the directory (we'll be using relative paths)
• make list of files with the given format
• make temporary directory and mount catfs there
• create recovery files for the archive.cat file in that directory
• unmount catfs and remove temporary directory

This way you'll save disk space on creating tar file (if, for some reason, you prefer to keep your backups as a spread of files instead of a single tarball), and still protect them from bit rot.

You need to keep cat.fs and all par2* files to be able to restore the files.

In case of damage to any file (say, important/data.txt), you can recover it this way:

cd backup/
mkdir mount && ~/catfs -s cat.fs mount
cp mount/archive.cat archive.cat
fusermount -u mount && rmdir mount
par2recover par2 archive.cat
~/uncat.sh cat.fs archive.cat important/data.txt

i.e.:

• go to the directory (again)
• make temporary directory and mount catfs there
• copy archive.cat out of the virtual file system
• unmount catfs and remove temporary directory
• recover broken archive.cat file
• extract recovered file from archive.cat

Note that this time, you have to copy whole archive.cat file out of the virtual filesystem. That's because catfs is implemented as read-only file system and under no circumstances will write to your files.

Based on a SSFS by MaaSTaaR: http://www.maastaar.net/fuse/linux/filesystem/c/2016/05/21/writing-a-simple-filesystem-using-fuse/

License: GNU GPL.