# badblocks > Search a device for bad blocks. > Some usages of badblocks can cause destructive actions, such as erasing all data on a disk, including the partition table. > More information: . - Search a disk for bad blocks by using a non-destructive read-only test: `sudo badblocks {{/dev/sdX}}` - Search an unmounted disk for bad blocks with a non-destructive read-write test: `sudo badblocks -n {{/dev/sdX}}` - Search an unmounted disk for bad blocks with a destructive write test: `sudo badblocks -w {{/dev/sdX}}` - Search an unmounted disk for bad blocks with a destructive write test and show verbose status: `sudo badblocks -svw {{/dev/sdX}}` - Search an unmounted disk in destructive mode and output found blocks to a file: `sudo badblocks -o {{path/to/file}} -w {{/dev/sdX}}` - Search an unmounted disk in destructive mode with improved speed using 4K block size and 64K block count: `sudo badblocks -w -b {{4096}} -c {{65536}} {{/dev/sdX}}`