signing a text file:-

zodiac@zodioc:~$ gpg --clearsign myfile

You need a passphrase to unlock the secret key for
user: "Celsius Thomas (My work key) "
1024-bit DSA key, ID 56B304BA, created 2010-04-03

original file has this content:- hello world


Then the signed file will look something like this:-


-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

hello world
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.9 (GNU/Linux)

iEYEARECAAYFAku3WEgACgkQvEorF1azBLrqgQCePziUoHP6zspKJhSfZRT+Fxfs
X/AAnRUevcz5vZ94dI1lhVH7ubdEissR
=jQ5/
-----END PGP SIGNATURE-----


Anyone who has your public key can check the signature in this file using gpg , thereby confirming that the file is from you.

Creating a detached Signature File

Problem

You want to sign a file digitally, but have the signature reside in a separate file

Solution:-

To create a binary format detached signature, myfile.sig :-
gpg --detach-sign myfile

To create an ASCII format detached signature, myfile.asc:-
gpg --detach-sign -a myfile

Discussion:-

A detached signature is placed into a file by itself, not inside the file it represents. Detached signatures are commonly used to validate sw distributed in compressed tar files , ex., myprogram.tar.gz. You can't sign such a file internally without altering its contents, so the signature is created in a separate file such as myprogram.tar.gz.sig

Encrypting Directories

To produce a single encrypted file containing all files in the directory, with symmetric encryption:

tar cvf -name_of_directory | gpg -c > files.tar.gpg

or key-based encryption:-

tar cvf -name_of_directory | gpg -e > files.tar.gpg

To encrypt each file separately:-

find name_of_directory -type f -exec gpg -e '{}' \;

Jet Airways Inflight Entertainment System uses Linux

sample squid configuration

Example Configurations

To help you fully understand how Squid access control works, and to give you a head start developing your own rules, the following are some ACL lines you can try. Each line is
preceded with one or more comment lines (starting with a #) explaining what it does:

# include the domains news.bbc.co.uk and slashdot.org
# and not newsimg.bbc.co.uk or www.slashdot.org.
acl newssites dstdomain news.bbc.co.uk slashdot.org
# include any subdomains or bbc.co.uk or slashdot.org
acl newssites dstdomain .bbc.co.uk .slashdot.org
# only include sites located in Canada
acl canadasites dstdomain .ca
# only include working hours

acl workhours time MTWHF 9:00-18:00
# only include lunchtimes
acl lunchtimes time MTWHF 13:00-14:00
# only include weekends
acl weekends time AS 00:00-23:59
# include URLs ending in “.zip”. Note: the \ is important,
# because “.” has a special meaning otherwise
acl zipfiles url_regex -i \.zip$
# include URLs starting with https
acl httpsurls url_regex -i ^https
# include all URLs that match “hotmail”
url_regex hotmail url_regex -i hotmail
# include three specific IP addresses
acl directors src 10.0.0.14 10.0.0.28 10.0.0.31
# include all IPs from 192.168.0.0 to 192.168.0.255
acl internal src 192.168.0.0/24
# include all IPs from 192.168.0.0 to 192.168.0.255
# and all IPs from 10.0.0.0 to 10.255.255.255
acl internal src 192.168.0.0/24 10.0.0.0/8

When you have your ACL lines in place, you can put together appropriate http_access lines. For example, you might want to use a multilayered access system so that certain
users (for example, company directors) have full access, whereas others are filtered. For example:

http_access allow directors
http_access deny hotmail
http_access deny zipfiles
http_access allow internal lunchtimes
http_access deny all

Because Squid matches those in order, directors will have full, unfiltered access to the Web. If the client IP address is not in the directors list, the two deny lines are processed so
that the user cannot download .zip files or read online mail at Hotmail. After blocking those two types of requests, the allow on line four allows internal users to access the Web,
as long as they do so only at lunchtime. The last line (which is highly recommended) blocks all other users from the proxy.

LVM + RAID

mdadm -C /dev/md0 --level=5 --raid-device=3 /dev/hda5 /dev/hda6 /dev/hda7

mkfs -t ext3 /dev/md0
pvcreate /dev/md0
vgcreate my-lvm-raid /dev/md0

lvcreate -L -500M -n my-lvm-raid-lv0 /dev/my-lvm-raid
mkfs -t ext3 /dev/my-lvm-raid/my-lvm-raid-lv0

mount /dev/my-lvm-raid/my-lvm-raid-lv0 /mnt


NB:- tested on Centos 5.3


see:- http://wiki.tldp.org/LVM-ON-RAID

chkconfig examples

chkconfig --list mysql
chkconfig service-name --level level-no: on/off
ex:- chkconfig firstboot --level 345 on
ec:- chkconfig firstboot off ; disables firstboot in all runlevels


NB:_ tested on ubuntu 9.04