What does the DD command flag 'if' specify?

The 'if' flag in the DD command specifies the input file. When using DD, it is essential to define where the source data is coming from; this is achieved with the 'if' option. This option tells DD which file or device to read the data from before performing any operations, such as copying or converting that data.

In practical terms, if you're copying data from a disk image or reading from a device like /dev/sda, you would use 'if=/path/to/source' to indicate the source from which DD should read the input data. This foundational understanding of the DD command is crucial when working with file systems, backups, or data recovery in Linux environments.