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<title> [筆記] 在 Linux 底下快速抹寫磁碟剩餘空間 | My cool new Blog</title>
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<h3><a href="/article/e7-ad-86-e8-a8-98-e5-9c-a8-linux-e5-ba-95-e4-b8-8b-e5-bf-ab-e9-80-9f-e6-8a-b9-e5-af-ab-e7-a3-81-e7-a2-9f-e5-89-a9-e9-a4-98-e7-a9-ba-e9-96-93/">[筆記] 在 Linux 底下快速抹寫磁碟剩餘空間</a></h3>
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<div class="meta">
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<span class="date moment">2015-11-25</span>
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<a href="/categories/%E6%9C%AA%E5%88%86%E9%A1%9E">未分類</a>
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</span>
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</div>
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<p>Update</p>
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<p>後來發現，其實內建的shred指令就可以做到了，而且速度更快～</p>
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<p>shred -v -n 10000(抹除 10000次) -u -v /dev/sda</p>
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<p>用iftop 看，大概都能維持在300M 左右的寫入速度</p>
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<p> </p>
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<p>實際跑起來，從 iotop 上看到的數據，似乎是比 dd 要來得快～</p>
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<p><a href="http://superuser.com/questions/19326/how-to-wipe-free-disk-space-in-linux">http://superuser.com/questions/19326/how-to-wipe-free-disk-space-in-linux</a></p>
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<p>Wipe a drive at top speed.</p>
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<p>Typical instructions for encrypting a drive nowadays will tell you to first WIPE the drive.</p>
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<p>The command below will fill your drive with AES ciphertext.</p>
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<p>Use a live CD if you need to wipe your main boot drive.</p>
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<p>Open a terminal and elevate your privileges:</p>
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<pre><code>sudo bash
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`</pre>
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Let us list all drives on the system to be safe:
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<pre>`cat /proc/partitions
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`</pre>
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NOTE: Replace<span class="Apple-converted-space"> </span>`/dev/sd{x}`<span class="Apple-converted-space"> </span>with the device you wish to wipe.
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WARNING: This is not for amateurs! You could make your system unbootable!!!
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`sudo openssl enc -aes-256-ctr -pass pass:"$(dd if=/dev/urandom bs=128 count=1 2&gt;/dev/null | base64)" -nosalt &lt; /dev/zero &gt; /dev/sd{x} `
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&nbsp;
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&nbsp;
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另外有一段也可以參考
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> &nbsp;
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</code></pre>
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<blockquote>
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<pre><code><pre>`# Install the secure-delete package (sfill command).
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# To see progress type in new terminal:
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# watch -n 1 df -hm
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# Assuming that there is one partition (/dev/sda1). sfill writes to /.
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# The second pass writes in current directory and synchronizes data.
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# If you have a swap partition then disable it by editing /etc/fstab
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# and use "sswap" or similar to wipe it out.
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# Some filesystems such as ext4 reserve 5% of disk space
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# for special use, for example for the /home directory.
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# In such case sfill won't wipe out that free space. You
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# can remove that reserved space with the tune2fs command.
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# See http://superuser.com/a/150757
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# and https://www.google.com/search?q=reserved+space+ext4+sfill
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sudo tune2fs -m 0 /dev/sda1
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sudo tune2fs -l /dev/sda1 | grep 'Reserved block count'
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sudo sfill -vfllz /
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# sfill with the -f (fast) option won't synchronize the data to
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# make sure that all was actually written. Without the fast option
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# it is way too slow, so doing another pass in some other way with
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# synchronization. Unfortunately this does not seem to be perfect,
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# as I've watched free space by running the "watch -n 1 df -hm"
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# command and I could see that there was still some available space
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# left (tested on a SSD drive).
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dd if=/dev/zero of=zero.small.file bs=1024 count=102400
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dd if=/dev/zero of=zero.file bs=1024
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sync ; sleep 60 ; sync
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rm zero.small.file
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rm zero.file
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sudo tune2fs -m 5 /dev/sda1
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sudo tune2fs -l /dev/sda1 | grep 'Reserved block count'
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</code></pre>
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</blockquote>
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by Lednerb
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