GSO, TSO and UFO ethtool for nic

Wonderful article at https://www.coverfire.com/articles/queueing-in-the-linux-network-stack/

Shadow file line

balatesting:$6$mgdrjbp6$CuWkPbZHHZpYanP5zJZWwS1awzdh4objOvsfJ.IrIqmYgu1.h5oIu.UvrMysy/NFaZEdS8Zm4jN8Mv/oJor.y.:17232:0:99999:7:::

Basic Email server in Ubuntu

Here we will see about the installation of a basic SMTP server on Ubuntu

$ sudo apt-get update # apt-get update –fix-missing # apt-get install bind9 dnsutils apache2 php5 postfix dovecot-common dovecot-imapd dovecot-pop3d squirrelmail

Click okay for Internet Site

Let us cd /etc/bind

# vim named.conf.local  be very careful about the style of quotes it is a normal double quote msword will put curly quotes which will not get interpreted correctly. zone “mark.net” {                    type master;                    file “/etc/bind/db.mark”; }; zone “0.168.192.in-addr.arpa” {                    type master;                    file “/etc/bind/db.192”; };

# cp db.local db.mark # cp db.127 db.192 # vim db.mark $TTL 604800 @   IN   SOA   ns.mark.net.   root.mark.net. (                                                2     ; Serial                                     604800     ; Refresh                                       86400     ; Retry                                   2419200    ; Expire                                        604800 ) ; Negative Cache TTL ; @         IN    NS           ns.mark.net. @         IN    A             192.168.0.1 ns         IN    A             192.168.0.1              IN    MX 10    mail.mark.net. www   IN    CNAME   ns mail     IN    CNAME   ns

# vim db.192 $TTL 604800 @   IN   SOA   ns.mark.net.   root.mark.net. (                                                1     ; Serial                                     604800     ; Refresh                                       86400     ; Retry                                   2419200    ; Expire                                        604800 ) ; Negative Cache TTL ; @         IN    NS           ns.mark.net. 1         IN    PTR      ns.mark.net

Now we will restart bind9

# invoke-rc.d bind9 restart

Now when we do nslookup mail.mark.net we should get the IP of our mail server.

When we do a dig mail.mark.net we should get answers from mark.db file of bind9 conf.

Now let us work on the configuration of apache2 configuration file.

# cd /etc/apache2/sites-available/ # ls -l # cp default mail.conf # vim mail.conf Now under VirutalHost directive under ServerAdmin let add the first line and update DocumentRoot                          ServerAdmin   webmaster@localhost                          ServerName    mail.mark.net                          DocumentRoot  /usr/share/squirrelmail # Change the next Directory line as shown below.

Next we should try to enable that site with # a2ensite mail

Then try to reload apache2 service.

 service apache2 reload

Now let us try to reconfigure postfix

# dpkg-reconfigure postfix Select Localonly and press Okay Then for System mail name: “mail.mark.net” and press OK. Then for Root and postmaster don’t give anything and press OK. Then for other destination to accept mail for change the line to mail.mark.net, mark-virtual-machine, localhost.localdomain, , localhost, mark.net Then for “Force synchronous updates on mail queue” press No Then in Local networks append 192.168.0.0/24 network Then leave the mailox size limit at 0 bytes. Then leave the * for Local address extension character and press Ok. Then for Internet Protocols to use press all and press OK.

Now let us edit the squirrelmail’s apache configuration file.

# vim /etc/squirrelmail/apache.conf Go down and uncomment DocumentRoot /usr/share/squirrelmail Edit the next line to this ServerName mail.mark.net vim.tiny /etc/squirrelmail/config.php $imapServerAddress      = '192.168.56.102'; $smtpServerAddress      = '192.168.56.102';

Now let us start editing the Dovecot configuration file.

# vim /etc/dovecot/dovecot.conf Go to the very bottom of the file and start typing protocols = imap pop3 #disable_plaintext_auth = no mail_location = mbox:~/mail:INBOX=/var/mail/%u #mail_location = maildir: ~/Maildir

Change this line alone in  /etc/postfix/main.cf

inet_interfaces = 192.168.56.102,127.0.0.1

Now that all configuration is over let us restart all the processes.

# killall named # killall apache2 # killall dovecot # invoke-rc.d bind9 restart # invoke-rc.d apache2 restart # invoke-rc.d postfix restart # invoke-rc.d dovecot restart

Now let us create a couple of users to try logging in as them for email transaction.

# adduser bala1 # adduser bala2

Then the important piece of information is to head to http://mail.mark.net/src/login.php

Shredding a disk securely

shred -vfz -n 10 /dev/sda5

-v: show progress

-f: change permissions to allow writing if necessary

-z: add a final overwrite with zeros to hide shredding

-n: overwrite N times instead of the default (3)

Serial Edit on VIM editor

When we need to use serial edit while on vim editor.

The following command will change from lines 3 to 7 all words of dogs in to cats.

:3,7s/dogs/cats/g

Hmmmm

Hmmm 5% increase per year

0.05	Per Month	Per Year	Cumulative
1st Year	23000	276000	276000
2nd Year	24150	289800	565800
3rd Year	25358	304290	870090
4th Year	26625	319505	1189595
5th Year	27957	335480	1525074
6th Year	29354	352254	1877328
7th Year	30822	369866	2247194
8th Year	32363	388360	2635554
9th Year	33981	407778	3043332
10th Year	35681	428167	3471498
11th Year	37465	449575	3921073
12th Year	39338	472054	4393127
13th Year	41305	495656	4888783
14th Year	43370	520439	5409222
15th Year	45538	546461	5955684
16th Year	47815	573784	6529468
17th Year	50206	602473	7131941
18th Year	52716	632597	7764538
19th Year	55352	664227	8428765
20th Year	58120	697438	9126203
21st Year	61026	732310	9858513
22nd Year	64077	768926	10627439
23rd Year	67281	807372	11434811
24th Year	70645	847741	12282552
25th Year	74177	890128	13172679

Openssl

This site has wonderful information and I have picked up a few command form it.

To check the contents of a Certificate Request file (csr)
$ openssl req -in server.csr -noout -text

To view the contents of a CA Signed certificate request file (cer)
$ openssl x509 -in server.cer -noout -text