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[rrq/fusefile.git] / fusefile.8

diff --git a/fusefile.8 b/fusefile.8
index b4bd50d314f7b3504677285e7660e1fbc17da885..f9ca25db611e0a89d1ef3ef2d4d4cf07abd1d316 100644 (file)
--- a/fusefile.8
+++ b/fusefile.8
@@ -4,7 +4,7 @@
 fusefile \- FUSE file mount for combining file fragments
 
 .SH SYNOPSIS
-.B fusefile \fR[fuse options\fR] \fBmountpoint\fR \fIfilename/from-to\fR ...
+.B fusefile \fR[\fIfuse-opts\fR] \fBmountpoint\fR \fR[\fIoverlay\fR] \fIfilename/from-to\fR ...
 
 .SH DESCRIPTION
 
@@ -15,6 +15,13 @@ as a 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
+\fB-overlay:\fIfilename\fR 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:
@@ -66,6 +73,34 @@ position 2442:
 \fB$ fusefile y x/2442: x/:2442\fR
 .RE
 
+Replace a partition in an image file with a different file
+.RS
+# Check the partition table
+.br
+\fB$ partx -oNR,START,SECTORS disk.raw\fR
+    NR   START  SECTORS
+     1    2048  2097152
+     2 2099200   409600
+     3 2508800 14268383
+.br
+# Replace partition 2 of 409600 sectors from 2099200 with
+.br
+# the file "insert.fat" clipped to 409600 sectors.
+.br
+\fB$ fusefile -ononempty disk.raw \\
+         disk.raw/0:$(( 2099200*512 )) \\
+         insert.fat/0:$(( 409600*512 )) \\
+         disk.raw/$(( (2099200+409600)*512 )):\fR
+.RE
+
+Protect raw disk image file with an overlay:
+.RS
+\fB$ fusefile -ononempty disk.raw -overlay:today disk.raw\fR
+.RE
+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.
+
 .SH NOTES
 
 Note that \fBfusefile\fR opens the nominated source file or files
@@ -75,10 +110,17 @@ descriptors remain open, but the source fragments are not recomputed.
 If a source file changes the fused file will present the new content.
 If a source is reduced in size, access will be inconsistent.
 
-If the mountpoint file doesn't exist, then \fBfusefile\fR creates it,
-and removes it when unmounted.
+If the mountpoint file doesn't exist, then \fBfusefile\fR creates it.
 
+Unmounting is done with "\fBfusermount -u\fR \fImountpoint\fR" 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.
 
 .SH AUTHOR
 
-Ralph Rönnquist <ralph.ronnquist@gmail.com>
+Ralph Rönnquist <ralph.ronnquist@gmail.com>.
+