Add initial version of nbdcanvas and nbdview program.

[libguestfs-talks.git] / 2019-fosdem / nbdview / README

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+nbdview is a small Tcl/Tk program that lets you visualize reads and
+writes happening to an nbdkit server in real time.
+
+To use it you will need to start your nbdkit server with the log
+filter.  For example, using the memory plugin (but any plugin may be
+used):
+
+  size=$((64 * 1024 * 1024))
+  nbdkit --filter=log memory size=$size logfile=/tmp/log
+
+Then start nbdview.tcl specifying the log file and virtual size:
+
+  ./nbdview.tcl /tmp/log $size &
+
+Note that only small disk sizes really work (larger sizes would
+require too many pixels!)  With the defaults compiled into
+nbdview.tcl: 4K block size, 128 x 128 pixel canvas, you can display at
+most 64MB.
+
+Then you can write to the NBD server using ordinary tools such as
+qemu, qemu-io, guestfish, etc. and observe the reads and writes to the
+disk.