Which command is used to check current disk usage in Linux?

The command that is widely used to check current disk usage in Linux, particularly for mounted filesystems, is df. This command provides a summary of available and used disk space on all mounted filesystems, displaying information such as the total size, used space, available space, and the mount point of each filesystem. By default, it shows the information in 1K blocks, but it can be modified to display sizes in human-readable formats (KB, MB, GB) using options like -h.

In contrast, while du is also related to disk usage, it is primarily used to estimate the disk space used by files and directories rather than providing an overview of overall mounted filesystem space. The ls command lists directory contents but does not provide any information about disk usage. The option disk_usage is not a standard command in Linux and does not exist in the command-line tools for checking disk usage. So, df is the most appropriate and correct command for checking current disk usage across mounted filesystems in Linux.