Added README.md

README.md

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+# Tar FUSE
+
+This program mounts a tar file system to a directory through FUSE.
+
+Have you ever wanted to have a nice, convenient view into a tar file without
+having to unpack it, and without having to learn a ton of obscure tar commands?
+Have you ever wanted to be able to do `find -type f -name "*.ml"`, or any other
+search command, only inside a tar file?
+
+If you've experienced any of the above, this is your lucky day! Just mount the
+tar file to a directory:
+
+```sh
+$ fusetar my-archive.tar mnt/
+```
+
+And just like that, everything inside the tarball is available to you as a
+read-only file system, to search, read or do whatever else.
+
+An example with the debian rootfs:
+
+```sh
+$ wget https://github.com/kbaraniak/debian-rootfs/releases/download/bookworm-270224/debian-amd64-bookworm-rootfs-270224.tar.xz
+...
+$ xz -d debian-amd64-bookworm-rootfs-270224.tar.xz
+$ mkdir -p mnt
+$ fusetar debian-amd64-bookworm-rootfs-270224.tar mnt/
+$ ls debian-amd64-bookworm-rootfs-270224.tar.xz
+bin  boot  dev  etc  home  lib  lib64  media  mnt  opt  proc  root  run  sbin  srv  sys  tmp  usr  var
+```
+
+As you can see, the root file system inside the tar archive is transparently presented to you now under your mounted directory!
+
+Note that it is read-only. Tar is a streaming format, and it is quite awkward to try to make changes/additions to it.
+
+With that being said, if you absolutely need to write files to the directory (but not to the archive), it is quite easy to make this directory writable - you can simply use overlayfs to overlay an empty directory over this mount. This way, your changes would be preserved inside a separate directory, while unchanged content from the archive remains available:
+
+```sh
+$ mkdir -p mnt/ upper/ workdir/ merged/ 
+$ ./main.exe debian-amd64-bookworm-rootfs-270224.tar -f mnt & 
+[1] 46526
+$ sudo mount -t overlay overlay -olowerdir=./mnt,upperdir=./upper,workdir=./workdir ./merged
+$ echo "hi" > merged/hello-world.txt
+$ ls -la merged
+total 5
+drwxr-xr-x 1 haxala1r users  30 Nov 27 17:37 .
+drwxr-xr-x 1 haxala1r users 362 Nov 27 17:36 ..
+lrwxrwxrwx 1 root     root    0 Jul  2  2023 bin -> usr/bin
+drwxr-xr-x 1 root     root    0 Jul  2  2023 boot
+drwxr-xr-x 1 root     root    0 Feb 27  2024 dev
+drwxr-xr-x 1 root     root    0 Feb 27  2024 etc
+-rw-r--r-- 1 haxala1r users   3 Nov 27 17:37 hello-world.txt
+drwxr-xr-x 1 root     root    0 Jul  2  2023 home
+lrwxrwxrwx 1 root     root    0 Jul  2  2023 lib -> usr/lib
+lrwxrwxrwx 1 root     root    0 Jul  2  2023 lib64 -> usr/lib64
+drwxr-xr-x 1 root     root    0 Jul  2  2023 media
+drwxr-xr-x 1 root     root    0 Jul  2  2023 mnt
+drwxr-xr-x 1 root     root    0 Jul  2  2023 opt
+drwxr-xr-x 1 root     root    0 Jul  2  2023 proc
+drwxr-xr-x 1 root     root    0 Feb 27  2024 root
+drwxr-xr-x 1 root     root    0 Jul  2  2023 run
+lrwxrwxrwx 1 root     root    0 Jul  2  2023 sbin -> usr/sbin
+drwxr-xr-x 1 root     root    0 Jul  2  2023 srv
+dr-xr-xr-x 1 root     root    0 Feb 27  2024 sys
+drwxr-xr-x 1 root     root    0 Jul  2  2023 tmp
+drwxr-xr-x 1 root     root    0 Jul  2  2023 usr
+drwxr-xr-x 1 root     root    0 Feb 27  2024 var
+```