Gentoo Archives: gentoo-user

From: Florian Philipp <lists@×××××××××××.net>
To: gentoo-user@l.g.o
Subject: Re: [gentoo-user] OT: blanking disk of linux appliance
Date: Mon, 14 Jan 2013 13:22:52
Message-Id: 50F40696.8050803@binarywings.net
In Reply to: [gentoo-user] OT: blanking disk of linux appliance by Adam Carter
1 Am 14.01.2013 03:11, schrieb Adam Carter:
2 > shred and dd available, but not srm etc
3 >
4 > I want to remove the user account info before the device is returned,
5 > but dont want to cripple the device. Filesystem is ext3 with default
6 > mount options, which implies its mounted with the default data=ordered,
7 > and according to the docs "In both the data=ordered (default) and
8 > data=writeback modes, shred works as usual"
9 >
10 > Would these steps be effective?
11 > - set root pw back to installation default
12 > - manually create copies of passwd and shadow (named passwd2 shadow2,
13 > NOT by copying files then deleting extra lines) containing only the
14 > default installation entries
15 > - shred /etc/passwd /etc/shadow
16
17 Don't forget the backup files created by some tools. For example
18 "/etc/passwd-"
19
20 > - mv passwd2 and shadow2 to passwd and shadow
21 > - dd if=/dev/zero of=/blah (to blank all spare blocks on fs, dd will
22 > bail out once full. Will it miss info from non-fully allocated blocks?)
23
24 Don't forget to do this as root to get the last 5%.
25
26 If you want to be sure, you can try several overwrite cycles, for
27 example with binary ones. The easiest way I know to generate such a
28 sequence is `tr '\000' '\377' < /dev/zero | dd of=...`. Or you can just
29 allocate /blah and then `shred` it.
30
31 > - rm /blah
32
33 If you have swap, you should clear that, too.
34
35 Regards,
36 Florian Philipp

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