It is generally safe to use the hdparm command to get or set hard disk parameters under Linux, as long as you use it with caution and follow the recommended guidelines for using the command.
The hdparm command can be used to perform various tasks related to hard disk drive (HDD) or solid state drive (SSD) configuration and optimization, such as setting the transfer mode, enabling or disabling write caching, or performing a hard disk self-test.
However, it is important to note that hdparm can also be used to perform potentially destructive operations, such as resetting the hard disk's internal error counters or wiping the entire drive. It is therefore recommended to be careful when using hdparm, and to make sure that you understand the potential consequences of the actions that you are performing.
In general, it is a good idea to make sure that you have a backup of any important data before using hdparm, and to exercise caution when modifying the parameters of your hard disk. It is also a good idea to consult the documentation for hdparm and for your specific hard disk model before using the command, as some parameters may not be supported or may have different effects on different types of disks.