How to calculate the Availability of application or server?

Avalaibility = 100 - 100 * (Unplanned Downtime / Uptime )


Availability % Downtime in Minutes  Downtime per Year   Vendor Jargon
90                     52,560.00              36.5 days                   one nine
99                     5,256.00                 4 days                        two nines
99.9                  525.60                    8.8 hours                    three nines
99.99                52.56                      53 minutes                  four nines
99.999              5.26                        5.3 minutes                 five nines
99.9999            0.53                        32 seconds                 six nines

Document on reverse Proxy

The below link have a good (infact best) document on reverse proxy for dummies
http://www.sans.org/reading_room/whitepapers/webservers/reverse-proxy-proxy-name_302

using scp command to transfer files between unix machines

scp command is used to transfer the files(directories) from one unix machine to another.Port 22 is used for scp.
Login to machine linux1 and you want to tranfer the file /opt/testfile to the /home/user1/ directory in machine linux2
#scp /opt/testfile user1@linux2:/home/user1/

If you want to copy the directory /opt/testdirectory then
#scp -r /opt/testdirectory user1@linux2:/home/user1/

The options for scp are

-p

Preserves the modification and access times, as well as the permissions of the source-file in the destination-file

-q

Do not display the progress bar

-r

Recursive, so it copies the contents of the source-file (directory in this case) recursively

-v

Displays debugging messages

webmin in solaris

Webmin package comes with the default installation of Solaris10
To setup webmin just run the command #webminsetup

apt-get in Linux

I installed the rpmforge (rpmforge-release-0.5.2-2.el5.rf.i386.rpm) from the DAG this link
When I use #apt-get update , it displayed an error saying that "Unable to resolve the dns name apt.sw.be"
The reason is ..I didnt update my /etc/resolv.conf with my DNS servers. After adding the DNS server IP address the problem is solved.

rsh login problem in linux

I have RHEL4 machine with IP address 10.121.113.92 and I want not able to connect to that server using rsh. Below are the steps followed by me to enable the rsh

[root@linux ~]# telnet 10.121.113.92 544
Trying 10.121.113.92...
telnet: connect to address 10.121.113.92: Connection refused
telnet: Unable to connect to remote host: Connection refused
=========================

In the file /etc/xinetd.d/rsh  make disable =no 

[root@linux ~]# more /etc/xinetd.d/rsh
 default: on
# description: The rshd server is the server for the rcmd(3) routine and, \
#       consequently, for the rsh(1) program.  The server provides \
#       remote execution facilities with authentication based on \
#       privileged port numbers from trusted hosts.
service shell
{
        disable = no
        socket_type             = stream
        wait                    = no
        user                    = root
        log_on_success          += USERID
        log_on_failure          += USERID
        server                  = /usr/sbin/in.rshd
}
====================================
In the file /etc/xinetd.d/rlogin  make disable =no 

[root@linux ~]# more /etc/xinetd.d/rlogin
# default: on
# description: rlogind is the server for the rlogin(1) program.  The server \
#       provides a remote login facility with authentication based on \
#       privileged port numbers from trusted hosts.
service login
{
        disable = no
        socket_type             = stream
        wait                    = no
        user                    = root
        log_on_success          += USERID
        log_on_failure          += USERID
        server                  = /usr/sbin/in.rlogind
}

=============
I then opened the /etc/pam.d/rlogin file and commented the "password " line and "auth       required    pam_securetty.so" line
Next I modified the line "auth required pam_rhosts_auth.so" to "auth sufficient pam_rhosts_auth.so"

[root@linux ~]# more /etc/pam.d/rlogin
#%PAM-1.0
# For root login to succeed here with pam_securetty, "rlogin" must be
# listed in /etc/securetty.
auth       required     pam_nologin.so
#auth       required    pam_securetty.so
auth       required     pam_env.so
auth       sufficient   pam_rhosts_auth.so
auth       required     pam_stack.so service=system-auth
account    required     pam_stack.so service=system-auth
#password   required     pam_stack.so service=system-auth
session    required     pam_stack.so service=system-auth


==========================
Commented "auth       required    pam_securetty.so" line in the /etc/pam.d/rsh file


[root@linux ~]# more /etc/pam.d/rsh
#%PAM-1.0
# For root login to succeed here with pam_securetty, "rsh" must be
# listed in /etc/securetty.
auth       required     pam_nologin.so
#auth       required    pam_securetty.so
auth       required     pam_env.so
auth       sufficient   pam_rhosts_auth.so
account    required     pam_stack.so service=system-auth
session    required     pam_stack.so service=system-auth

==============

[root@linux ~]# more /etc/pam.d/rexec
#%PAM-1.0
# For root login to succeed here with pam_securetty, "rexec" must be
# listed in /etc/securetty.
auth       required     pam_nologin.so
auth       required     pam_securetty.so
auth       required     pam_env.so
auth       required     pam_stack.so service=system-auth
account    required     pam_stack.so service=system-auth
session    required     pam_stack.so service=system-auth

===================

Added rsh,rlogin,rexec to /etc/securetty

[root@linux ~]# more /etc/securetty
console
vc/1
vc/2
vc/3
vc/4
vc/5
vc/6
vc/7
vc/8
vc/9
vc/10
vc/11
tty1
tty2
tty3
tty4
tty5
tty6
tty7
tty8
tty9
tty10
tty11
rsh
rlogin
rexec
=====================

Created the /root/.rhosts file with 644 permission and added the host name/IP address from which this server will be rsh connected

[root@linux ~]# more /root/.rhosts
10.121.113.95
first.test.com

================

[root@linux ~]# hostname
linux.test.com
==========

[root@linux ~]# more /etc/hosts
# Do not remove the following line, or various programs
# that require network functionality will fail.
127.0.0.1         localhost.localdomain   localhost
10.121.113.92   linux.test.com
10.121.113.94   first.test.com
10.121.113.95   second.test.com

==============

restarted the xinetd services

[root@linux ~]# chkconfig --list | grep rsh
        rsh:    on
[root@linux ~]# chkconfig --list | grep rlogin
        rlogin: on
===============

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