FreeBSD9.0開始支持ssd的trim指令，但安裝系統時需要通過newfs -t方式啓用trim，否則默認不啓用，如果安裝時沒有啓用，也可以通過tunefs命令啓用trim：
1、進入單用戶模式
2、#mount
#tunefs -t enable /dev/ada0p3
3、查看
#tunefs -p /dev/ada0p3
tunefs: POSIX.1e ACLs: (-a) disabled
tunefs: NFSv4 ACLs: (-N) disabled
tunefs: MAC multilabel: (-l) disabled
tunefs: soft updates: (-n) enabled
tunefs: soft update journaling: (-j) enabled
tunefs: gjournal: (-J) disabled
tunefs: trim: (-t)
enabled
tunefs: maximum blocks per file in a cylinder group: (-e) 4096
tunefs: average file size: (-f) 16384
tunefs: average number of files in a directory: (-s) 64
tunefs: minimum percentage of free space: (-m) 8%
tunefs: optimization preference: (-o) time
tunefs: volume label: (-L)
注意tunefs只能操作umont或read-only的文件系統，詳細見tunefs(8)