完全用 GNU/Linux 工作
30. 銷毀資料 - Shred
過去在 GNU/Linux 裡，凍仁會使用 dd，此指令會將資料填零而達到抹除磁碟的功用，但就算這樣還是有被專業人士還原的風險；現在凍仁都改用 shred指令來完成這項任務，此指令是專門用來撕碎資料的。
dd
將 /dev/sdX 裝置填零。
dd if=/dev/zero of=/dev/sdX bs=1M
shred
開始 shred 之前，您必須先安裝 coreutils 套件。
$ sudo aptitude install coreutils # -v 顯示進度。 # -f 強制寫入，必要時允許變更權限寫入。 # -z 用零覆寫並撕碎。 # -n 指定覆寫次數。 # -n 指定覆寫次數。抹除硬碟
$ sudo shred -vfz -n 10 /dev/sdX shred: /dev/sdX：11 次之第 1 次 (random)... shred: /dev/sdX：11 次之第 1 次 (random)...471MiB/932GiB 0% shred: /dev/sdX：11 次之第 1 次 (random)...472MiB/932GiB 0% shred: /dev/sdX：11 次之第 1 次 (random)...949MiB/932GiB 0% ......抹除檔案
$ shred -vu -n 10 hello-sherd.txt shred: hello-sherd.txt: pass 1/3 (random)... shred: hello-sherd.txt: pass 2/3 (random)... shred: hello-sherd.txt: pass 3/3 (random)... shred: hello-sherd.txt: removing shred: hello-sherd.txt: renamed to 000000000000000 shred: 000000000000000: renamed to 00000000000000 shred: 00000000000000: renamed to 0000000000000 shred: 0000000000000: renamed to 000000000000 shred: 000000000000: renamed to 00000000000 shred: 00000000000: renamed to 0000000000 shred: 0000000000: renamed to 000000000 shred: 000000000: renamed to 00000000 shred: 00000000: renamed to 0000000 shred: 0000000: renamed to 000000 shred: 000000: renamed to 00000 shred: 00000: renamed to 0000 shred: 0000: renamed to 000 shred: 000: renamed to 00 shred: 00: renamed to 0 shred: hello-sherd.txt: removed
※ shred 在 ext3, ext4 這類的日誌檔案系統上運作時可能無法完整清除，若真不放心可以試試 hdparm。