Combines the random access indexing idea from tarindexer and then mounts the TAR using fusepy for easy read-only access just like archivemount. It also will mount TARs inside TARs inside TARs, ... recursively into folders of the same name, which is useful for the ImageNet data set. Furthermore, it now has support for BZip2 compressed TAR archives provided by indexed_bzip2, a refactored and extended version of bzcat from toybox, and support for Gzip compressed TAR archives provided by the indexed_gzip dependency.
You can simply install it from PyPI:
pip install ratarmount
Or, if you want to test the latest development version on a Debian-like system:
sudo apt-get update
sudo apt-get install python3 python3-pip git
git clone https://github.com/mxmlnkn/ratarmount.git
python3 -m pip install --user .
ratarmount --help
You can also simply download ratarmount.py and call it directly after installing the dependencies manually with: pip3 install --user fusepy indexed_bzip2
.
If you want to use other serialization backends instead of the default SQLite one, e.g., because you still have indexes lying around created with those backends and don't want to spend time recreating them, then you'll have to install a version older than 0.5.0 with the optional legacy-serializers
feature:
pip install ratarmount[legacy-serializers]==0.4.1
usage: ratarmount.py [-h] [-f] [-d DEBUG] [-c] [-r]
[-gs GZIP_SEEK_POINT_SPACING] [-p PREFIX] [-o FUSE] [-v]
mount_source [mount_source ...] [mount_point]
With ratarmount, you can:
- Mount a TAR file to a folder for read-only access
- Bind mount a folder to another folder for read-only access
- Union mount a list of TARs and folders to a folder for read-only access
positional arguments:
mount_source The path to the TAR archive to be mounted. If multiple
archives and/or folders are specified, then they will
be mounted as if the arguments coming first were
updated with the contents of the archives or folders
specified thereafter, i.e., the list of TARs and
folders will be union mounted.
mount_point The path to a folder to mount the TAR contents into.
If no mount path is specified, the TAR will be mounted
to a folder of the same name but without a file
extension. (default: None)
optional arguments:
-h, --help show this help message and exit
-f, --foreground Keeps the python program in foreground so it can print
debug output when the mounted path is accessed.
(default: False)
-d DEBUG, --debug DEBUG
Sets the debugging level. Higher means more output.
Currently, 3 is the highest. (default: 1)
-c, --recreate-index If specified, pre-existing .index files will be
deleted and newly created. (default: False)
-r, --recursive Mount TAR archives inside the mounted TAR recursively.
Note that this only has an effect when creating an
index. If an index already exists, then this option
will be effectively ignored. Recreate the index if you
want change the recursive mounting policy anyways.
(default: False)
-gs GZIP_SEEK_POINT_SPACING, --gzip-seek-point-spacing GZIP_SEEK_POINT_SPACING
This only is applied when the index is first created
or recreated with the -c option. The spacing given in
MiB specifies the seek point distance in the
uncompressed data. A distance of 16MiB means that
archives smaller than 16MiB in uncompressed size will
not benefit from faster seek times. A seek point takes
roughly 32kiB. So, smaller distances lead to more
responsive seeking but may explode the index size!
(default: 16)
-p PREFIX, --prefix PREFIX
[deprecated] Use "-o modules=subdir,subdir=<prefix>"
instead. This standard way utilizes FUSE itself and
will also work for other FUSE applications. So, it is
preferable even if a bit more verbose.The specified
path to the folder inside the TAR will be mounted to
root. This can be useful when the archive as created
with absolute paths. E.g., for an archive created with
`tar -P cf /var/log/apt/history.log`, -p /var/log/apt/
can be specified so that the mount target directory
>directly< contains history.log. (default: )
-o FUSE, --fuse FUSE Comma separated FUSE options. See "man mount.fuse" for
help. Example: --fuse
"allow_other,entry_timeout=2.8,gid=0". (default: )
-v, --version Print version string. (default: False)
# Metadata Index Cache
In order to reduce the mounting time, the created index for random access
to files inside the tar will be saved to these locations in order. A lower
location will only be used if all upper locations can't be written to.
1. <path to tar>.index.sqlite
2. ~/.ratarmount/<path to tar: '/' -> '_'>.index.sqlite
E.g., ~/.ratarmount/_media_cdrom_programm.tar.index.sqlite
# Bind Mounting
The mount sources can be TARs and/or folders. Because of that, ratarmount
can also be used to bind mount folders read-only to another path similar to
"bindfs" and "mount --bind". So, for:
ratarmount folder mountpoint
all files in folder will now be visible in mountpoint.
# Union Mounting
If multiple mount sources are specified, the sources on the right side will be
added to or update existing files from a mount source left of it. For example:
ratarmount folder1 folder2 mountpoint
will make both, the files from folder1 and folder2, visible in mountpoint.
If a file exists in both multiple source, then the file from the rightmost
mount source will be used, which in the above example would be "folder2".
If you want to update / overwrite a folder with the contents of a given TAR,
you can specify the folder both as a mount source and as the mount point:
ratarmount folder file.tar folder
The FUSE option -o nonempty will be automatically added if such a usage is
detected. If you instead want to update a TAR with a folder, you only have to
swap the two mount sources:
ratarmount file.tar folder folder
# File versions
If a file exists multiple times in a TAR or in multiple mount sources, then
the hidden versions can be accessed through special <file>.versions folders.
For example, consider:
ratarmount folder updated.tar mountpoint
and the file "foo" exists both in the folder and in two different versions
in "updated.tar". Then, you can list all three versions using:
ls -la mountpoint/foo.versions/
dr-xr-xr-x 2 user group 0 Apr 25 21:41 .
dr-x------ 2 user group 10240 Apr 26 15:59 ..
-r-x------ 2 user group 123 Apr 25 21:41 1
-r-x------ 2 user group 256 Apr 25 21:53 2
-r-x------ 2 user group 1024 Apr 25 22:13 3
In this example, the oldest version has only 123 bytes while the newest and
by default shown version has 1024 bytes. So, in order to look at the oldest
version, you can simply do:
cat mountpoint/foo.versions/1
You downloaded a large TAR file from the internet, for example the 1.31TB large ImageNet, and you now want to use it but lack the space, time, or a file system fast enough to extract all the 14.2 million image files.
Archivemount seems to have large performance issues for too many files for both mounting and file access in version 0.8.7. A more in-depth comparison benchmark can be found here.
time cat mounted/ILSVRC2012_val_00049975.JPEG | wc -c
takes 250ms for archivemount and 2ms for ratarmount.Tarindex is a command line to tool written in Python which can create index files and then use the index file to extract single files from the tar fast. However, it also has some caveats which ratarmount tries to solve:
I didn't find out about TAR Browser before I finished the ratarmount script. That's also one of it's cons:
Pros:
Ratarmount creates an index file with file names, ownership, permission flags, and offset information to be stored at the TAR file's location or inside ~/.ratarmount/
and then offers a FUSE mount integration for easy access to the files.
The test with the first version (50e8dbb), which used the removed pickle backend for serializing the metadata index, for the ImageNet data set is promising:
The reading time for a small file simply verifies the random access by using file seek to be working. The difference between the first read and subsequent reads is not because of ratarmount but because of operating system and file system caches.
Here is a more recent test for version 0.2.0 with the new default SQLite backend:
During the making of this project several benchmarks were created. These can be viewed here. These are some of the things benchmarked and compared there: