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RECOVERDISK(1)		FreeBSD	General	Commands Manual		RECOVERDISK(1)

     recoverdisk -- recover data from hard disk	or optical media

     recoverdisk [-b bigsize] [-r readlist] [-s	interval] [-w writelist]
		 source	[destination]

     The recoverdisk utility reads data	from the source	file until all blocks
     could be successfully read.  If destination was specified all data	is
     being written to that file.  It starts reading in multiples of the	sector
     size.  Whenever a block fails, it is put to the end of the	working	queue
     and will be read again, possibly with a smaller read size.

     By	default	it uses	block sizes of roughly 1 MB, 32kB, and the native sec-
     tor size (usually 512 bytes).  These figures are adjusted slightly, for
     devices whose sectorsize is not a power of	2, e.g., audio CDs with	a sec-
     tor size of 2352 bytes.

     The options are as	follows:

     -b	bigsize
	     The size of reads attempted first.	 The middle pass is roughly
	     the logarithmic average of	the bigsize and	the sectorsize.

     -r	readlist
	     Read the list of blocks and block sizes to	read from the speci-
	     fied file.

     -s	interval
	     How often we should update	the writelist file while things	go OK.
	     The default is 60 and the unit is "progress messages" so if
	     things go well, this is the same as once per minute.

     -w	writelist
	     Write the list of remaining blocks	to read	to the specified file
	     if	recoverdisk is aborted via SIGINT.

     The -r and	-w options can be specified together.  Especially, they	can
     point to the same file, which will	be updated on abort.

     The recoverdisk utility prints several columns, detailing the progress

     start	Starting offset	of the current block.

     size	Read size of the current block.

     len	Length of the current block.

     state	Is increased for every failed read.

     done	Number of bytes	already	read.

     remaining	Number of bytes	remaining.

     % done	Percent	complete.

     # recover data from failing hard drive ada3
     recoverdisk /dev/ada3 /data/disk.img

     # clone a hard disk
     recoverdisk /dev/ada3 /dev/ada4

     # read an ISO image from a	CD-ROM
     recoverdisk /dev/cd0 /data/cd.iso

     # continue	reading	from a broken CD and update the	existing worklist
     recoverdisk -r worklist -w	worklist /dev/cd0 /data/cd.iso

     # recover a single	file from the unreadable media
     recoverdisk /cdrom/file.avi file.avi

     # If the disk hangs the system on read-errors try:
     recoverdisk -b 0 /dev/ada3	/somewhere

     dd(1), ada(4), cam(4), cd(4), da(4)

     The recoverdisk utility first appeared in FreeBSD 7.0.

     The original implementation was done by Poul-Henning Kamp
     <> with minor improvements from Ulrich Sporlein

     This manual page was written by Ulrich Sporlein.

     Reading from media	where the sectorsize is	not a power of 2 will make all
     1 MB reads	fail.  This is due to the DMA reads being split	up into	blocks
     of	at most	128kB.	These reads then fail if the sectorsize	is not a divi-
     sor of 128kB.  When reading a full	raw audio CD, this leads to roughly
     700 error messages	flying by.  This is harmless and can be	avoided	by
     setting -b	to no more than	128kB.

     recoverdisk needs to know about read errors as fast as possible, i.e.
     retries by	lower layers will usually slow down the	operation.  When using
     cam(4) attached drives, you may want to set to
     zero, e.g.:

     # sysctl
     # sysctl
     # sysctl

FreeBSD	11.0			October	1, 2013			  FreeBSD 11.0


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