Linux Ask!

Linux Ask! is a Q & A web site specific for Linux related questions. Questions are collected, answered and audited by experienced Linux users.

Jun 162013
 

How to trace DNS from the root servers

Answer:

Use the command `dig`, e.g.

dig +trace mit.edu

;; global options: +cmd
.			19927	IN	NS	d.root-servers.net.
.			19927	IN	NS	e.root-servers.net.
.			19927	IN	NS	m.root-servers.net.
.			19927	IN	NS	l.root-servers.net.
.			19927	IN	NS	a.root-servers.net.
.			19927	IN	NS	k.root-servers.net.
.			19927	IN	NS	f.root-servers.net.
.			19927	IN	NS	j.root-servers.net.
.			19927	IN	NS	b.root-servers.net.
.			19927	IN	NS	h.root-servers.net.
.			19927	IN	NS	g.root-servers.net.
.			19927	IN	NS	i.root-servers.net.
.			19927	IN	NS	c.root-servers.net.
;; Received 228 bytes from 8.8.8.8#53(8.8.8.8) in 12 ms

edu.			172800	IN	NS	a.edu-servers.net.
edu.			172800	IN	NS	c.edu-servers.net.
edu.			172800	IN	NS	d.edu-servers.net.
edu.			172800	IN	NS	f.edu-servers.net.
edu.			172800	IN	NS	g.edu-servers.net.
edu.			172800	IN	NS	l.edu-servers.net.
;; Received 260 bytes from 199.7.83.42#53(199.7.83.42) in 223 ms

mit.edu.		172800	IN	NS	usw2.akam.net.
mit.edu.		172800	IN	NS	asia1.akam.net.
mit.edu.		172800	IN	NS	asia2.akam.net.
mit.edu.		172800	IN	NS	use2.akam.net.
mit.edu.		172800	IN	NS	ns1-37.akam.net.
mit.edu.		172800	IN	NS	ns1-173.akam.net.
mit.edu.		172800	IN	NS	eur5.akam.net.
mit.edu.		172800	IN	NS	use5.akam.net.
;; Received 404 bytes from 192.31.80.30#53(192.31.80.30) in 548 ms

mit.edu.		20	IN	A	23.46.134.151
;; Received 41 bytes from 63.150.131.81#53(63.150.131.81) in 4 ms
Mar 242011
 

Allow a remote IP for incoming connection in UFW (Uncomplicated firewall)

Answer:

To allow a remote IP for incoming connection in Ubuntu's UFW (Uncomplicated firewall), you can use the following command:

# sudo ufw allow from x.x.x.x

Of course you need to reload the firewall.

# sudo ufw reload