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random.4: Rework example scripts to assume 'poolsize' unit is bits, not bytes 

Reported-by: Tom Gundersen <teg@jklm.no>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
This commit is contained in:
Michael Kerrisk 2015-12-17 08:47:27 +01:00
parent 0594459d21
commit 3f4a2adb06
1 changed files with 9 additions and 3 deletions
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12
man4/random.4
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@ -171,7 +171,7 @@ This reduces the actual amount of noise in the entropy pool
below the estimate.
In order to counteract this effect, it helps to carry
entropy pool information across shut-downs and start-ups.
To do this, add the following lines to an appropriate script
To do this, add the lines to an appropriate script
which is run during the Linux system start-up sequence:
.nf
@ -186,7 +186,8 @@ which is run during the Linux system start-up sequence:
fi
chmod 600 $random_seed
poolfile=/proc/sys/kernel/random/poolsize
[ \-r $poolfile ] && bytes=\`cat $poolfile\` || bytes=512
[ \-r $poolfile ] && bits=\`cat $poolfile\` || bits=4096
bytes=$(expr $bits / 8)
dd if=/dev/urandom of=$random_seed count=1 bs=$bytes
.fi
@ -201,9 +202,14 @@ run during the Linux system shutdown:
touch $random_seed
chmod 600 $random_seed
poolfile=/proc/sys/kernel/random/poolsize
[ \-r $poolfile ] && bytes=\`cat $poolfile\` || bytes=512
[ \-r $poolfile ] && bits=\`cat $poolfile\` || bits=4096
bytes=$(expr $bits / 8)
dd if=/dev/urandom of=$random_seed count=1 bs=$bytes
.fi
In the above examples, we assume Linux 2.6.0 or later, where
.IR /proc/sys/kernel/random/poolsize
returns the size of the entropy pool in bits (see below).
.SS /proc Interface
The files in the directory
.I /proc/sys/kernel/random