From bbe5314bf498f2f6b07e88617ec2d10ee30004b0 Mon Sep 17 00:00:00 2001 From: Ralph Ronnquist Date: Sat, 13 Aug 2022 08:49:43 +1000 Subject: [PATCH] editorial revision --- README.adoc | 113 ++++++++-------------------------------------------- 1 file changed, 17 insertions(+), 96 deletions(-) diff --git a/README.adoc b/README.adoc index efd47b2..ffc927c 100644 --- a/README.adoc +++ b/README.adoc @@ -1,105 +1,26 @@ -fusefile -======== -:colon: : -:noop: +# fusefile This project implements a "fuse" device to mount as a single file that is a concatenation of fragments of one or more files. The fused file -allows overwriting the parts files, but not changing their sizes, and -only for parts files that are writable upon first access. - -FUSE file mount for combining file fragments. - -== SYNOPSIS +allows overwriting to fragments but not changing their sizes and only +for writable fragment files. A fused file may also be set up with an +overlay file in which case that file will capture all changes instead +of changing the underlying fragment files. ==== -*fusefile* [ _fuse options_ ] *mountpoint* [ _overlay_ ] +_filename_/from:to+ ... +This is a nominal usage example to set up a fused file C consisting of +files A and B: +---- +$ fusefile C A B +---- ==== -## DESCRIPTION - -*fusefile* is FUSE file mount that presents a series of fragments of -other files as a contiguous concatenation. It bind mounts a driver on -top of the file mountpoint to present the nominated file fragments as -a single, contiguous file. single, contiguous file. It accepts -over-writing on the fused file which gets distributed accordingly to -the fragments, but cannot change size. - -An optional overlay file is declared with an -**-overlay:**__filename__ argument between the mount point and -the fragments. This file is then set up as an overlay for capturing -writes to the fused file. The overlay file will contain the written -fused file regions, followed by meta data to distinguish between -written content and "holes" (where content comes from the fused -fragments). - -The fragment arguments include the filename of a source file, and -optionally start and end byte positions. All in all there five -variations: - - * __filename__ include all of the file. - - * __filename/__ include all of the file named with "/" in the pathname. This case requires a final "/", since the last "/" separates the filename from the position details. - - * __filename/from__ include the file from the given start position, to end. - - * __filename/-to__ include the file from beginning to the given end position (not included). - - * __filename/from:to__ include the file from the given start position, up to the given end position (not included). - -## EXAMPLES - -.Insert file "y" into file "x" at position 1200: - - $ fusefile -ononempty x x/:1200 y x/1200: - -That mount will shadow the original file "x", and presents the -fused file instead. - -.Make file y be a swap of the beginning and end of file "x", at position 2442: - - $ fusefile y x/2442: x/:2442 - -.Replace a partition in an image file with a different file - - $ partx -oNR,START,SECTORS disk.raw - NR START SECTORS - 1 2048 2097152 - 2 2099200 409600 - 3 2508800 14268383 - # Replace partition 2 of 409600 sectors from 2099200 with - # the file "insert.fat" clipped to 409600 sectors. - $ fusefile -ononempty disk.raw \ - disk.raw/0:$(( 2099200*512 )) \ - insert.fat/0:$(( 409600*512 )) \ - disk.raw/$(( (2099200+409600)*512 )): - -.Protect raw disk image file with an overlay: - $ fusefile -ononempty disk.raw -overlay:today disk.raw - -By that set up, the overlay file, "today", will protect the disk image -file, "disk.raw" from changes, and also override the pathname -"disk.raw" to be the fused file. - - -## NOTES - -Note that **fusefile** opens the nominated source file(s) before bind -mounting. With the fuse option __-ononempty__ it will bind over an -non-empty file, which may be useful. The source file descriptors -remain open, but the source fragments are not recomputed. If a source -file changes or reduces in size "behind" the fused file, then anything -may happen. - -If the mountpoint file doesn't exist, then **fusefile** creates it. - -Unmounting is done with "**fusermount -u** __mountpoint__" as usual. - -Using an overlay file makes the fused file writable regardless of the -fused fragments with the overlay file containing any changes to the -original. The overlay file is reusable for subsequent fusing of the -same fragments for reconstructing a prior session with changes. +==== +This is a nominal example of tearing down a fused file X: +---- +$ fusermount -u C +---- +==== -## AUTHOR +See the +man page+ for usage details and some more examples. -Ralph Rönnquist . -- 2.39.2