Linux FUSE driver to create disk images consisting of collection of small individual files.
MosaicFS is a Linux FUSE driver to create and access disk images. Rather than being stored as a single large file, the content of the disk image is stored as a collection of individual small files (a mosaic of tile files). The disk image file has a fixed size defined at creation, but the individual tile files storing its content are created dynamically as content is added.
When used in combination with standard Linux tools, MosaicFS provides a functionality similar to MacOS sparse bundle disk images. Note however that MosaicFS is not and never will be compatible with sparse bundle disk images.
The initial motivation for MosaicFS was to create disk images that are sparse and can grow dynamically as content is added. Moreover, because the content is stored as a collection of tile files, these disk images can be easily be mirrored to a remote server or cloud storage without having to replicate the entire image every time.
cd src
makemosaicfs --help
Usage: mosaicfs <command> [options]
Available commands and options:
mosaicfs mount <archive> <path> [--fuse="<fuse arguments>"]
Mount existing MosaicFS archive located in directory <archive> on mount
point <path>. <path> will be created if necessary. If <path> exists, it
should be an empty file.
--fuse="<...>" optional mount arguments to be passed to FUSE.
mosaicfs create --number <number of tiles> --size <tile size> <archive>
Create new MosaicFS archive under directory <archive> with total size
<number of tiles> x <tile size>:
-n / --number N number of tile files
-s / --size S size of each individual tile file. Default size is in
bytes, but other units are also available by appending
their appropriate units (K = kilobyte, M = megabyte,
G = gigabyte).mosaicfs create --number <number of tiles> --size <tile size> <archive>
mosaicfs create --number 8192 --size 128M disk.imgCreate a new MosaicFS disk image under the directory 'disk.img'. The size of the disk image is 1 TB (8192 x 128 MB) and its content will be stored in 8192 tile files, each 128 MB in size.
mosaicfs mount <archive> <path>
mosaicfs mount disk.img disk
Mount with FUSE the MosaicFS disk image 'disk.img' under 'disk'. After mounting, 'disk' will appear as a a file of the size of the MosaicFS image. 'disk' can be mounted as a loopback device and a file system can be created on it. See next section for specific examples.
fusermount -u <path>
fusermount -u diskCreate a new MosaicFS 100 GB in size, consisting of 800x128 MB tile files. Create and ext4 file system and mount it.
mosaicfs create --number=800 --size=128M drive.img
mosaicfs mount drive.img drive --fuse="-o allow_root"
mkfs.ext4 drive
sudo mkdir -p /media/mydrive
sudo mount -o loop drive /media/mydriveThe fuse option "-o allow_root" is needed in order for root to be able to access the image file. Alternatively, one can also mount MosaicFS as root:
sudo mosaicfs mount drive.img drivebut some might find it objectionable to mount a Fuse file system as root.
Mount a previously created disk image
mosaicfs mount drive.img drive --fuse="-o allow_root"
sudo mkdir -p /media/mydrive
sudo mount -o loop drive /media/mydrivesudo umount /media/mydrive
sudo rmdir /media/mydrive
fusermount -u driveSimilar to the previous example, but adding an encryption layer using dm-crypt.
# Create and Fuse mount MosaicFS
mosaicfs create --number=800 --size=128M drive.img
mosaicfs mount drive.img drive --fuse="-o allow_root"
# Find next available loopback device
sudo losetup -f
# Create loopback device
sudo losetup /dev/loop0 drive
# Create encryption layer
sudo cryptsetup -y -v luksFormat /dev/loop0
# Open encryption layer
sudo cryptsetup luksOpen /dev/loop0 drive
#--> block device is under /dev/mapper/drive
# Create file system
sudo mkfs.ext4 /dev/mapper/drive
# Mount file system
sudo mkdir -p /media/mydrive
sudo mount /dev/mapper/drive /media/mydrive# Fuse mount MosaicFS
mosaicfs mount drive.img drive --fuse="-o allow_root"
# Find next available loopback device
sudo losetup -f
# Create loopback device
sudo losetup /dev/loop0 drive
# Open encryption layer
sudo cryptsetup luksOpen /dev/loop0 drive
#--> block device is under /dev/mapper/drive
# Mount file system
sudo mkdir -p /media/mydrive
sudo mount /dev/mapper/drive /media/mydrivesudo umount /media/mydrive
sudo rmdir /media/mydrive
sudo cryptsetup luksClose drive
sudo losetup -d /dev/loop0
fusermount -u driveElements of MosaicFS were inspired by concatfs which allows read-only access to a concatenation of files. MosaicFS would not have been possible without the wonderful Fuse project and its documentation and tutorials.
Although MosaicFS has undergone a fair amount of testing, it is provided AS-IS without any warranty. Before using it for mission critical applications, you should perform due diligence and ensure that it meets your needs. See LICENSE for full disclaimer.
Chris Lazgo
chris.lazgo at gmx.com