Fuse filesystem for dynamically-enlarged file (can be mounted as loop device too)
usage: ./dynfilefs -f storage_file -m mount_dir [ -s size_MB ] [ -p split_size_MB ] [ -d ]
Mount filesystem to [mount_dir], provide a virtual file [mount_dir]/virtual.dat of size [size_MB] All changes made to virtual.dat file are stored to [storage_file] file(s)
-d - Debug mode; do not fork to background
--file [storage_file]
[storage_file]
-f [storage_file] - Path to the file where changes to the virtual file will be stored.
- The storage file is created with the provided name to store metadata,
and then additional storage files are created with the same base name
with extension suffixes such as .0, .1, .2, etc.
- If the storage exists, it will be reused.
--mountdir [mount_dir]
[mount_dir]
-m [mount_dir] - Specifies the directory where the filesystem will be mounted.
- The directory must be empty, or the mount operation will be refused.
--size [size_MB]
-o size=[size_MB]
-s [size_MB] - Sets the size of the virtual.dat file in MB.
- If storage file exists, you can specify bigger size_MB than before,
in that case the size of virtual file will be enlarged.
- If the specified size_MB is smaller than before, it will be ignored
and the previous stored value of size_MB will be reused.
- If the size is specified as +size_MB (note the plus sign prefix),
then the virtual file will grow by size_MB if storage_file exists.
--split [split_size_MB]
-o split=[split_size_MB]
-p [split_size_MB ] - Sets the maximum data size per storage file. Multiple files
will be created if [size_MB] > [split_size_MB].
Beware that actual file size (including internal indexes) may be
bigger than split_size_MB, so use max 4088 on FAT32 to be safe,
because FAT32 does not support individual files bigger than 4GB.
- This parameter is ignored if storage file exists,
in that case the previous stored value is reused.
Example usage:
./dynfilefs -f /tmp/changes.dat -s 1024 -m /mnt
mke2fs -F /mnt/virtual.dat
mount -o loop /mnt/virtual.dat /mnt
Usage in fstab
/var/lib/changes.dat /var/lib/changes dynfilefs size=1024,split=1000 0 0
/var/lib/changes/virtual.dat /extra auto loop 0 0
How to compile:
./autogen.sh
./configure
make
How to compile statically:
DynFileFS can be statically compiled with buildroot, but it's a bit tricky.
Read buildroot/README for more information. Tested on buildroot-2025.02.4
Pre-built static binary for newest version can be found in ./static/ directory.
Master branch is work in progress, may be broken. See releases for "stable" versions. Latest version is 4.03 (2023) Releases can be found here: https://github.com/Tomas-M/dynfilefs/releases