在此節錄 # man secureleve 中有關 secure level 影響的說明 -1 Permanently insecure mode - always run the system in insecure mode. This is the default initial value.
0 Insecure mode - immutable and append-only flags may be turned off. All devices may be read or written subject to their permissions.
1 Secure mode - the system immutable and system append-only flags may not be turned off; disks for mounted file systems, /dev/mem and /dev/kmem may not be opened for writing; /dev/io (if your platform has it) may not be opened at all; kernel modules (see kld(4)) may not be loaded or unloaded.
2 Highly secure mode - same as secure mode, plus disks may not be opened for writing (except by mount(2)) whether mounted or not. This level precludes tampering with file systems by unmounting them, but also inhibits running newfs(8) while the system is multi- user.
我的桌機因為要跑 X window 所以只能用 "-1" 但是在 server 上建議使用 1 或 2, 我是用 "2"