Which command is recommended for checking partition alignment on a disk?

The command that is recommended for checking partition alignment on a disk is gdisk. Gdisk is a partitioning tool that supports GPT (GUID Partition Table), which is essential for managing disks larger than 2TB and provides better features compared to the traditional MBR (Master Boot Record). One of the functionalities of gdisk is that it can check partitions for proper alignment, which is particularly important for performance on modern storage devices like SSDs. Proper alignment can minimize read and write amplification, resulting in better overall performance and longevity of the storage medium.

In contrast, while fdisk is a commonly used tool for managing disks and partitions, it primarily supports MBR and lacks the features necessary for optimizing or checking alignment on GPT disks. The commands swapon -s and mount -a do not relate to partition alignment at all; swapon -s is used to report swap usage, and mount -a is used to mount filesystems listed in /etc/fstab. Hence, these do not serve any purpose in checking the alignment of partitions.