Author: AlekZ

Why does x^0 equal 1?

Since basic school we know, that [math]x^0=1[/math], but only recently when our kids began to study mathematics we asked ourselves “why?”.

I came up with this explanation:

[math]x^0=x^{n-n}=x^n \times x^{-n}=\frac {x^n} {x^n}=1[/math]

Also a good test for the Easy LaTeX WordPress plug-in.

And here’s jsxgraph plug-in test:
Continue reading “Why does x^0 equal 1?”

How to downmix 4 channels into 2

Or a quadraphonic record into a stereo one.

Le’s assume you have a bunch of files in one directory. The following script will downmix 4 channels into 2 with the following proportions:

  • LF => 100% LF
  • RF => 100% RF
  • LB => 100% LF
  • RB => 100% RF

and move the stereo files into a directory called “stereo”:

mkdir stereo
for file in $*
do
  sox -S -c4 "$file" -c2 stereo/"$file" mixer  1,1
done

If you want to change the front/back ratio to, for example:

  • LF => 100% LF
  • RF => 100% RF
  • LB => 70% LF
  • RB => 70% RF

the sox command will look like:

sox -S -c4 "$file" -c2 stereo/"$file" mixer  1,0.7

How to migrate a zone with shared to exclusive IP-stack

“Old” Solaris approach: a zone with exclusive IP-stack requires a separate physical network interface.

“New” Solaris 11 (project Crossbow, beginning b105) approach: you have one physical interface and you do with it whatever you want. You can create a whole network within your single box and a single network card.

Here’s an example on how to migrate your existing zones with shared stack to “independent” zones.

Old configuration: one global zone (system name xeon), one non-global zone (dmz), one physical interface (e1000g0), two VLAN’s (1 and 10):

xeon# ifconfig -a


e1000g1000:  #VLAN 1 (global zone)
flags=201000843 mtu 9000 index 3
inet 10.0.1.100 netmask ffffff00 broadcast 10.0.1.255
ether 0:18:f3:ef:2a:d0

e1000g1000:1: #VLAN 1 (zone dmz)
flags=201000843 mtu 9000 index 3
inet 10.0.1.101 netmask ffffff00 broadcast 10.0.1.255
ether 0:18:f3:ef:2a:d0

e1000g10000:  #VLAN 10 (zone dmz)
flags=201000842 mtu 9000 index 5
inet 10.0.0.100 netmask 0
ether 0:18:f3:ef:2a:d0

xeon# cd /etc/zones
xeon# more dmz.xml
. . .

. . .

“Defrouters” are defined in the global zone. So, if the global zone has a defaultrouter set to 10.0.1.1, you will have this route in zone “dmz”. You can’t get rid of it and force the traffic to 10.0.0.1. Instead you will have two default routes in both zones.

Now, let’s have a look at the virtual interfaces (a part of the new concept).
Currently we do not have any:

xeon# dladm show-vnic
xeon#

Let’s create two virtual interfaces, each of them will belong to a separate VLAN. You can choose a name for a virtual interface and call it whatever (almost 😉 ) you want:

xeon# dladm create-vnic -l e1000g0 -v 10 dmz0
xeon# dladm create-vnic -l e1000g0 -v 1 dmz1


xeon# dladm show-vnic
LINK OVER SPEED MACADDRESS MACADDRTYPE VID
dmz1 e1000g0 1000 2:8:20:fb:6a:82 random 1
dmz0 e1000g0 1000 2:8:20:52:8e:c5 random 10

Now we have two virtual interfaces:

  • dmz1 – VLAN 1
  • dmz0 – VLAN 10

with randomly assigned MAC addresses. You can assign an arbitrary MAC address to a virtual interface or use a factory one. (see man dladm).

Reconfigure the zone:

xeon# zonecfg -z dmz
zonecfg:dmz> info
. . .
net:
address: 10.0.0.100
physical: e1000g10000
defrouter: 10.0.0.1
net:
address: 10.0.1.101
physical: e1000g1000
defrouter: 10.0.1.1
. . .
zonecfg:dmz> set ip-type=exclusive
zonecfg:dmz> remove net address=10.0.0.100
zonecfg:dmz> remove net address=10.0.1.10
zonecfg:dmz> add net
zonecfg:dmz:net> set physical=dmz0
zonecfg:dmz:net> end
zonecfg:dmz> add net
zonecfg:dmz:net> set physical=dmz1
zonecfg:dmz:net> end
zonecfg:dmz> info
. . .
ip-type: exclusive
. . .
net:
address not specified
physical: dmz0
defrouter not specified
net:
address not specified
physical: dmz1
defrouter not specified
zonecfg:dmz> commit
zonecfg:dmz> exit

Now, (re)boot your zone and configure the network interfaces and default routes as if they were on a standalone system.

xeon# netstat -rn | fgrep defa
default 10.0.1.1 UG 1 12408
xeon# zlogin -C dmz
. . .
dmz# ifconfig -a
dmz0: flags=201000843 mtu 9000 index 2
inet 10.0.0.100 netmask ffffff00 broadcast 10.0.0.255
ether 2:8:20:52:8e:c5


dmz1: flags=201000843 mtu 9000 index 3
inet 10.0.1.101 netmask ffffff00 broadcast 10.0.1.255
ether 2:8:20:fb:6a:82

dmz# netstat -rn | fgrep defa
default 10.0.0.1 UG 1 5156

Nice! I love Solaris …

Site “safety” testers

Here you can test if a site is listed in any of the available black lists:

http://www.robtex.com/dns/DOMAINNAME.html
http://www.robtex.com/ip/IPADDRESS.html
http://hosts-file.net/?s=DOMAINNAME
https://www.trustedsource.org/en/feedback/url
http://www.siteadvisor.com/sites/DOMAINNAME
http://www.trustedsource.org/TS?do=feedback&subdo=query&q=DOMAINNAME
http://www.malwaredomainlist.com/mdl.php?search=DOMAINNAME&colsearch=All&quantity=50
http://www.google.com/safebrowsing/diagnostic?site=http://WEBSITEURL
http://www.mywot.com/en/scorecard/DOMAINNAME