| From: | Noah Misch <noah(at)leadboat(dot)com> |
|---|---|
| To: | Marko Kreen <markokr(at)gmail(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Postgres Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: pgcrypto seeding problem when ssl=on |
| Date: | 2013-01-14 13:00:42 |
| Message-ID: | 20130114130042.GB26919@tornado.leadboat.com |
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| Thread: | |
| Lists: | pgsql-hackers |
On Mon, Jan 14, 2013 at 02:21:00PM +0200, Marko Kreen wrote:
> Note: reading from /dev/urandom does not affect /dev/random.
Reading from /dev/urandom drains the pool that serves /dev/random:
$ cat /proc/sys/kernel/random/entropy_avail
3596
$ dd iflag=nonblock bs=100 count=1 if=/dev/random of=/dev/null
1+0 records in
1+0 records out
100 bytes (100 B) copied, 0.000174798 s, 572 kB/s
$ cat /proc/sys/kernel/random/entropy_avail
2839
$ head -c10000000 /dev/urandom >/dev/null
$ cat /proc/sys/kernel/random/entropy_avail
212
$ dd iflag=nonblock bs=100 count=1 if=/dev/random of=/dev/null
0+1 records in
0+1 records out
38 bytes (38 B) copied, 0.000101439 s, 375 kB/s
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