Which command allows you to check for available disk space on all mounted filesystems?

The command that allows you to check for available disk space on all mounted filesystems is df -h. When you run this command, it reports the amount of disk space used and available on all currently mounted file systems in a human-readable format, making it easier to understand at a glance.

The -h option stands for "human-readable," and it translates sizes into more manageable units like KB, MB, and GB, instead of displaying raw bytes. This is particularly useful for system administrators or users who need to monitor disk usage and ensure that there is sufficient space available for their applications and data.

Other choices serve different purposes: the free command provides information about memory usage rather than disk space. The diskusage command is not a standard command in most Linux distributions, making it an invalid choice for this task. The lsblk command displays block device information, which includes details about partitions and their sizes but does not specifically focus on available disk space for mounted filesystems. Thus, df -h is the command that specifically meets the requirement of checking available disk space.