File: ddrescue.info,  Node: Important advice,  Next: Algorithm,  Prev: Basic concepts,  Up: Top

3 Using ddrescue safely
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Ddrescue is like any other power tool. You need to understand what it does,
and you need to understand some things about the machines it does those
things to, in order to use it safely.

   Never try to rescue a r/w mounted partition. The resulting copy may be
useless. It is best that the device or partition to be rescued is not
mounted at all, not even read-only.

   Never try to repair a file system on a drive with I/O errors; you will
probably lose even more data.

   If you use a device or a partition as destination, any data stored there
will be overwritten.

   Some systems may change device names on reboot (for example, udev enabled
systems). If you reboot such a system, pass the option '--ask' to ddrescue
and check that the device names match the model and serial number of the
input and output devices before allowing ddrescue to proceed. You may also
check the devices with commands like 'hdparm -I /dev/sda' or
'smartctl -i /dev/sda'.

   If you interrupt the rescue and then reboot, any partially copied
partitions should be hidden before allowing them to be touched by any
operating system that tries to mount and "fix" the partitions it sees.

   When using a (graphical) frontend, be careful to not insert or remove any
devices to avoid changes in the mapping of devices to device names between
the moment the devices are selected in the frontend and the call to
ddrescue. Be careful even if the frontend passes '--ask' to ddrescue,
because OUTFILE may be changed between user confirmation and actual opening.