Which command would provide detailed information about filesystems and their block groups?

The command that provides detailed information about filesystems and their block groups is "dumpe2fs." This command is specifically designed for ext2, ext3, and ext4 filesystems, and it outputs extensive information about a filesystem, including its superblock, block group information, and several other key attributes.

Using "dumpe2fs," users can examine various attributes of a filesystem such as block sizes, the number of inodes, the location of block groups, and the number of free blocks, among other details. This level of detail is particularly beneficial for system administrators who need to troubleshoot filesystem issues or perform maintenance.

The other commands serve different purposes: "fsck" is utilized for checking and repairing filesystems, "rune2fs" is not a standard Linux command and may be a typographical error or misrepresentation, and "mdadm" is related to managing Linux software RAID arrays, not filesystems themselves. Therefore, "dumpe2fs" stands out as the appropriate choice for obtaining detailed filesystem information.