3 Using ddrescue safely

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.

Always use a logfile unless you know you won’t need it. Without a logfile, ddrescue can’t resume a rescue, only reinitiate it.

Never try to rescue a r/w mounted partition. The resulting copy may be useless.

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 (eg. udev enabled systems). If you reboot, check the device names before restarting ddrescue.

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.