Hi you all, I have a BIG performance problem on an Sun E3500, the scenario is described below:
I have several users (30) accessing via samba to the E3500 using an application built on Visual Foxpro from their Windows PC , the problem is that the first guy that logs in demands 30% of the E3500... (2 Replies)
Hello,
i have a a1000 connected to an e6500. There's a raid 10 (12 disks) on the a1000.
If i do a
dd if=/dev/zero of=/mnt/1 bs=1024k count=1000
and then look at iostat it tells me there's a kw/s of 25000.
But if i do a
dd of=/dev/zero if=/mnt/1 bs=1024k count=1000
then i see only a... (1 Reply)
Hello,
I'm running a script on AIX to process lines in a file. I need to enclose the second column in quotation marks and write each line to a new file. I've come up with the following:
#!/bin/ksh
filename=$1
exec >> $filename.new
cat $filename | while read LINE
do
echo $LINE | awk... (2 Replies)
Hello all
We just built a storage cluster for our new xenserver farm. Using 3ware 9650SE raid controllers with 8 x 1TB WD sata disks in a raid 5, 256KB stripe size.
While making first performance test on the local storage server using dd (which simulates the read/write access to the disk... (1 Reply)
Hello,
we have a machine with Solaris Express 11, 2 LSI 9211 8i SAS 2 controllers (multipath to disks), multiport backplane, 16 Seagate Cheetah 15K RPM disks.
Each disk has a sequential performance of 220/230 MB/s and in fact if I do a
dd if=/dev/zero of=/dev/rdsk/<diskID_1> bs=1024k... (1 Reply)
Hello guys,
I have two servers performing the same disk operations. I believe one server is having a disk's impending failure however I have no hard evidence to prove it. This is a pair of Netra 210's with 2 drives in a hardware raid mirror (LSI raid controller). While performing intensive... (4 Replies)
Hi,
I am new registered user here in this UNIX forums.
I am a new system administrator for AIX 6.1. One of our servers performs poorly every time our application (FINACLE) runs many processes/instances. (see below for topas snapshot)
I use NMON or Topas to monitor the server utilization. I... (9 Replies)
Hi
We have an M3000 single physical processor and 8gb of memory running Solaris 10. This system runs two Oracle Databases one on Oracle 9i and One on Oracle 10g.
As soon as the Oracle 10g database starts we see an immediate drop in system performance, for example opening an ssh session can... (6 Replies)
Just a quick note for macOS users.
I just installed (and removed) Parallels Desktop 15 Edition on my MacPro (2013) with 64GB memory and 12-cores, which is running the latest version of macOS Catalina as of this post. The reason for this install was to test some RIGOL test gear software which... (6 Replies)
Discussion started by: Neo
6 Replies
LEARN ABOUT REDHAT
urandom
RANDOM(4) Linux Programmer's Manual RANDOM(4)NAME
random, urandom - kernel random number source devices
DESCRIPTION
The character special files /dev/random and /dev/urandom (present since Linux 1.3.30) provide an interface to the kernel's random number
generator. File /dev/random has major device number 1 and minor device number 8. File /dev/urandom has major device number 1 and minor
device number 9.
The random number generator gathers environmental noise from device drivers and other sources into an entropy pool. The generator also
keeps an estimate of the number of bit of the noise in the entropy pool. From this entropy pool random numbers are created.
When read, the /dev/random device will only return random bytes within the estimated number of bits of noise in the entropy pool.
/dev/random should be suitable for uses that need very high quality randomness such as one-time pad or key generation. When the entropy
pool is empty, reads to /dev/random will block until additional environmental noise is gathered.
When read, /dev/urandom device will return as many bytes as are requested. As a result, if there is not sufficient entropy in the entropy
pool, the returned values are theoretically vulnerable to a cryptographic attack on the algorithms used by the driver. Knowledge of how to
do this is not available in the current non-classified literature, but it is theoretically possible that such an attack may exist. If this
is a concern in your application, use /dev/random instead.
CONFIGURING
If your system does not have /dev/random and /dev/urandom created already, they can be created with the following commands:
mknod -m 644 /dev/random c 1 8
mknod -m 644 /dev/urandom c 1 9
chown root:root /dev/random /dev/urandom
When a Linux system starts up without much operator interaction, the entropy pool may be in a fairly predictable state. 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 informa-
tion across shut-downs and start-ups. To do this, add the following lines to an appropriate script which is run during the Linux system
start-up sequence:
echo "Initializing kernel random number generator..."
# Initialize kernel random number generator with random seed
# from last shut-down (or start-up) to this start-up. Load and
# then save 512 bytes, which is the size of the entropy pool.
if [ -f /var/random-seed ]; then
cat /var/random-seed >/dev/urandom
fi
dd if=/dev/urandom of=/var/random-seed count=1
Also, add the following lines in an appropriate script which is run during the Linux system shutdown:
# Carry a random seed from shut-down to start-up for the random
# number generator. Save 512 bytes, which is the size of the
# random number generator's entropy pool.
echo "Saving random seed..."
dd if=/dev/urandom of=/var/random-seed count=1
FILES
/dev/random
/dev/urandom
AUTHOR
The kernel's random number generator was written by Theodore Ts'o (tytso@athena.mit.edu).
SEE ALSO
mknod (1)
RFC 1750, "Randomness Recommendations for Security"
Linux 1997-08-01 RANDOM(4)