The UNIX ssh program is used to establish a secure login on a remote machine. It encrypts all communication between the local machine and the remote machine. On a Windows platform, an ssh login can be established using the PuTTY program.
Here is an example of a secure shell login to ukko.d.umn.edu. Everything typed by the the user is shown with a light green background.
susan 1% ssh email@example.com The authenticity of host 'ukko.d.umn.edu (126.96.36.199)' can't be established. RSA key fingerprint is cc:47:75:ae:85:c4:7c:fb:1e:a7:5b:cf:76:0b:b9:5b. Are you sure you want to continue connecting (yes/no)? yes Warning: Permanently added 'ukko.d.umn.edu,188.8.131.52' (RSA) to the list of known hosts. firstname.lastname@example.org's password: Welcome to Ubuntu 12.04.1 LTS (GNU/Linux 3.2.0-35-generic x86_64) * Documentation: https://help.ubuntu.com/ System information as of Wed Jan 16 08:15:27 CST 2013 System load: 0.11 Processes: 268 Usage of /: 40.1% of 45.83GB Users logged in: 1 Memory usage: 1% IP address for bond0: 184.108.40.206 Swap usage: 0% Graph this data and manage this system at https://landscape.canonical.com/ 33 packages can be updated. 12 updates are security updates. Last login: Mon Jan 14 08:33:57 2013 from 68-115-86-83.dhcp.roch.mn.charter.com ukko 1%
A common use of the ping program is to time a connection to a remote machine.
Here is an example using ping to time the connection to bitsy.mit.edu. Everything typed by the the user is shown with a light green background. Note that you need to type a control-C to terminate the ping.
ukko 1% ping bitsy.mit.edu PING bitsy.mit.edu: 56 data bytes 64 bytes from BITSY.MIT.EDU (220.127.116.11): icmp_seq=0. time=57. ms 64 bytes from BITSY.MIT.EDU (18.104.22.168): icmp_seq=1. time=56. ms 64 bytes from BITSY.MIT.EDU (22.214.171.124): icmp_seq=2. time=58. ms 64 bytes from BITSY.MIT.EDU (126.96.36.199): icmp_seq=3. time=57. ms 64 bytes from BITSY.MIT.EDU (188.8.131.52): icmp_seq=4. time=56. ms 64 bytes from BITSY.MIT.EDU (184.108.40.206): icmp_seq=5. time=56. ms 64 bytes from BITSY.MIT.EDU (220.127.116.11): icmp_seq=6. time=57. ms 64 bytes from BITSY.MIT.EDU (18.104.22.168): icmp_seq=7. time=56. ms 64 bytes from BITSY.MIT.EDU (22.214.171.124): icmp_seq=8. time=57. ms ^C ----bitsy.mit.edu PING Statistics---- 9 packets transmitted, 9 packets received, 0% packet loss round-trip (ms) min/avg/max = 56/56/58
The UNIX nslookup program can be used to determine a variety of information about machines and domains in the internet. It uses the Domain Name System (DNS) protocol to query DNS name servers. There is at least one DNS name server for each internet domain. This is explained further in the "Name Server" subsection.
The primary purpose of DNS is translating host names to Internet Protocol (IP) addresses. IP addresses are required for routing data through the internet.
For security reasons, most machines and domains will not respond to all types of queries made by nslookup. Most will respond to the query types described in the following sections. In these examples everything typed by the the user is shown with a light blue background.
Here is an example using nslookup to find the address of bulldog.d.umn.edu. The first two lines give the local server from which the query originates. They are the same in all of the examples below. The answer to the query is in the following lines.
ukko 1% nslookup -type=a bulldog.d.umn.edu Server: 126.96.36.199 Address: 188.8.131.52#53 Name: bulldog.d.umn.edu Address: 184.108.40.206
Here is an example using nslookup to find the mail exchanger for a network domain. A non-authoritative answer means the local DNS server is returning information that it had cached from earlier queries.
There are two kinds of IP addresses in the section that describes where you can get authoritative information:
ukko 2% nslookup -type=mx tc.umn.edu Server: 220.127.116.11 Address: 18.104.22.168#53 Non-authoritative answer: tc.umn.edu mail exchanger = 10 mhub-m.tc.umn.edu. tc.umn.edu mail exchanger = 10 mhub-w.tc.umn.edu. tc.umn.edu mail exchanger = 10 mhub-a.tc.umn.edu. Authoritative answers can be found from: umn.edu nameserver = ns-auth-2.umn.edu. umn.edu nameserver = ns-auth-1.umn.edu. umn.edu nameserver = ns-auth-remote-1.umn.edu. ns-auth-1.umn.edu internet address = 22.214.171.124 ns-auth-1.umn.edu has AAAA address 2001:468:1910:4801::2 ns-auth-2.umn.edu internet address = 126.96.36.199 ns-auth-2.umn.edu has AAAA address 2001:468:1910:4802::2 ns-auth-remote-1.umn.edu internet address = 188.8.131.52
Here are examples using nslookup to find the name server for a domain. A domain is an administrative unit for a group of machines. The administrative units form a hierarchy.
The full hostname for a machine encodes the domains it belongs to. For example
Domains at any level can be queried for their name server. The first example show a query for a lower-level domain. The second example show a query for a higher-level domain.
ukko 3% nslookup -type=ns mit.edu Server: 184.108.40.206 Address: 220.127.116.11#53 Non-authoritative answer: mit.edu nameserver = W20NS.mit.edu. mit.edu nameserver = bitsy.mit.edu. mit.edu nameserver = STRAWB.mit.edu. Authoritative answers can be found from: bitsy.mit.edu internet address = 18.104.22.168 W20NS.mit.edu internet address = 22.214.171.124 STRAWB.mit.edu internet address = 126.96.36.199
ukko 4% nslookup -type=ns edu Server: 188.8.131.52 Address: 184.108.40.206#53 Non-authoritative answer: edu nameserver = l.edu-servers.net. edu nameserver = c.edu-servers.net. edu nameserver = a.edu-servers.net. edu nameserver = g.edu-servers.net. edu nameserver = f.edu-servers.net. edu nameserver = d.edu-servers.net. Authoritative answers can be found from: a.edu-servers.net internet address = 220.127.116.11 c.edu-servers.net internet address = 18.104.22.168 d.edu-servers.net internet address = 22.214.171.124 f.edu-servers.net internet address = 126.96.36.199 g.edu-servers.net internet address = 188.8.131.52 g.edu-servers.net has AAAA address 2001:503:cc2c::2:36 l.edu-servers.net internet address = 184.108.40.206
Here is an example using traceroute to trace the route to bitsy.mit.edu. Everything typed by the the user is shown with a light green background.
ukko 1% traceroute bitsy.mit.edu traceroute to bitsy.mit.edu (220.127.116.11), 30 hops max, 60 byte packets 1 18.104.22.168 (22.214.171.124) 0.397 ms 0.412 ms 0.472 ms 2 hh-L3-exchange-631.d.umn.edu (126.96.36.199) 0.445 ms 0.526 ms 0.590 ms 3 dlh-cb-01-po-2-4010.ggnet.umn.edu (188.8.131.52) 0.507 ms 0.638 ms 0.806 ms 4 192.168.212.194 (192.168.212.194) 6.413 ms 6.425 ms 6.415 ms 5 172.25.1.117 (172.25.1.117) 6.389 ms 6.401 ms 6.406 ms 6 172.25.0.146 (172.25.0.146) 6.365 ms 6.259 ms 6.301 ms 7 172.25.1.178 (172.25.1.178) 6.544 ms 6.644 ms 6.705 ms 8 172.25.0.38 (172.25.0.38) 6.478 ms 6.570 ms 6.658 ms 9 telecomb-bn-02-v3210.ggnet.umn.edu (184.108.40.206) 6.415 ms 6.334 ms 6.422 ms 10 telecomb-br-02-v3219.ggnet.umn.edu (220.127.116.11) 6.325 ms 6.384 ms 6.427 ms 11 telecomb-br-01-te-4-2.ggnet.umn.edu (18.104.22.168) 6.321 ms 6.301 ms 6.364 ms 12 telecomb-gr-01-te-2-3.northernlights.gigapop.net (22.214.171.124) 6.298 ms 6.293 ms 6.343 ms 13 infotech-gr-01-te-2-1.northernlights.gigapop.net (126.96.36.199) 6.419 ms 6.324 ms 6.350 ms 14 nlr.northernlights.gigapop.net (188.8.131.52) 17.292 ms 17.284 ms 17.175 ms 15 vlan-63.clev.layer2.nlr.net (184.108.40.206) 40.436 ms 40.455 ms 40.839 ms 16 vlan-62.newy.layer2.nlr.net (220.127.116.11) 40.532 ms 40.377 ms 40.581 ms 17 18.104.22.168 (22.214.171.124) 40.354 ms 40.351 ms 40.345 ms 18 DMZ-RTR-1-NY32-RTR-1.MIT.EDU (126.96.36.199) 50.243 ms 50.427 ms 50.423 ms 19 BACKBONE-RTR-1-DMZ-RTR-1.MIT.EDU (188.8.131.52) 46.701 ms 46.726 ms 46.754 ms 20 W92-RTR-1-BACKBONE-2.MIT.EDU (184.108.40.206) 46.836 ms 46.785 ms 46.813 ms 21 BITSY.MIT.EDU (220.127.116.11) 46.740 ms !X 46.746 ms !X 46.739 ms !X