A. The defragfs command should not be run against file systems and logical volumes that contain mostly transitory information， such as /tmp.
B. The defragfs command should not be run on a large JFS2 file system when running on a 32-bit kernel.
C. The defragfs command can improve file system performance by increasing the file system’s contiguous free space.
D. The defragfs command can only be run against file systems that are mounted with read-write permissions.