Some Famous Unix Commands
1. Famous Unix directories and files include the following:
/
- called "slash", the top level directory
/etc
- directory containing system configuration files
and management command, rhymes with Betsy
/etc/hosts, /etc/services, /etc/protocols
- famous network files
/etc/resolv.conf, /etc/passwd, /etc/groups - more configuration files
/bin, /usr/bin, /usr/local/bin,
- directories of commands
/sbin, /usr/sbin, /usr/local/sbin
- superuser commands
/home
- user home directories
2. The man command (e.g. "man telnet") can be used to get more information
on any of the following commands.
3. If you enter a command (e.g. ping) and receive the message "Command not
found", it usually means that Unix is not looking in the directory that
contains the command. If this happens, try "whereis ping", then "cd" to
the correct directory and reenter the command. (For a permanent fix, edit
the "path" statement in the file ".login").
4. "telnet astro.temple.edu" - to log in to astro.temple.edu (very insecure).
5. "ssh stafford@astro.temple.edu" - to log in to stafford's account on
astro.temple.edu using secure shell (encrypted password and data).
6. "ftp ftp.rfc-editor.org" - transfer a file from ftp.rfc-editor. Log in using
account "anonymous" with your E-mail address as password. Try "dir",
"cd in-notes", "ascii", "dir" again, and finally "get rfc791.txt". Use
"bye" to exit ftp and "more rfc-index.txt" to read the document.
(To do all of this automatically, enter the web address
"ftp://ftp.rfc-editor.org/in-notes/rfc791.txt" in your browser.)
7. "more /etc/hosts" to see your local "internet name and address" file
8. "more /etc/protocols" to see what protocols can be carried in IP packets.
9. "more /etc/services" to see the ports are used by "well known" services.
10. "more /etc/resolv.conf" to see the nameservers your computer uses.
11. "ping www.temple.edu" - to see if computer www.temple.edu is alive and
reachable.
12. "arp -a" to print Ethernet and IP address of other active computers on
your LAN
13. "ifconfig to see your computer's Ethernet and IP addresses.
14. "netstat -nr" to print your computer's IP routing tables
15. "netstat -lut" (Listening Udp or Tcp sockets) to see the network services
offered on Linux based systems.
16. "netstat -af inet | grep LISTEN" to see the network services on Sun or Dec
Unix systems.
17. "netstat -i" to see statistics on packets sent and received.
18. "nslookup www.temple.edu" to find IP address of computer www.temple.edu
19. "nslookup", then "?" to do a lot more.
20. "traceroute www.bucks.edu" to determine the path to "www.bucks.edu"
Results of executing Networking commands on the Linux system in my office.
1. linux:~ # ifconfig
eth0
Link encap:Ethernet HWaddr 00:50:04:D3:C0:CA
inet addr:192.168.1.102 Bcast:192.168.1.255 Mask:255.255.255.0
inet6 addr: fe80::250:4ff:fed3:c0ca/64 Scope:Link
UP BROADCAST NOTRAILERS RUNNING MULTICAST MTU:1500 Metric:1
RX packets:2517 errors:0 dropped:0 overruns:0 frame:0
TX packets:2057 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:100
RX bytes:1493378 (1.4 Mb) TX bytes:217474 (212.3 Kb)
Interrupt:10 Base address:0x1000
lo
Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:30 errors:0 dropped:0 overruns:0 frame:0
TX packets:30 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:1956 (1.9 Kb) TX bytes:1956 (1.9 Kb)
2. linux:~ # netstat -lut
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address
tcp
0
0 *:sunrpc
tcp
0
0 *:x11
tcp
0
0 localhost:smtp
tcp
0
0 *:ssh
udp
0
0 *:bootpc
udp
0
0 *:sunrpc
3. linux:~ # netstat -i
Kernel Interface table
Iface
MTU Met RX-OK RX-ERR RX-DRP RX-OVR
eth0
1500
0 2528
0
0
0
lo
16436
0
30
0
0
0
Foreign Address
*:*
*:*
*:*
*:*
*:*
*:*
State
LISTEN
LISTEN
LISTEN
LISTEN
TX-OK TX-ERR TX-DRP TX-OVR Flg
2062
0
0
0 BMNRU
30
0
0
0 LRU
4. linux:~ # /sbin/arp -a
? (192.168.1.147) at 00:06:5B:52:1D:70 [ether] on eth0
? (192.168.1.1) at 00:04:5A:F3:D9:E1 [ether] on eth0
5. linux:~ # ping www.bucks.edu
PING www.bucks.edu (192.231.233.6) 56(84) bytes of data.
64 bytes from www.bucks.edu (192.231.233.6): icmp_seq=1 ttl=47
64 bytes from www.bucks.edu (192.231.233.6): icmp_seq=2 ttl=47
64 bytes from www.bucks.edu (192.231.233.6): icmp_seq=3 ttl=47
64 bytes from www.bucks.edu (192.231.233.6): icmp_seq=4 ttl=47
--- www.bucks.edu ping statistics --4 packets transmitted, 4 received, 0% packet loss, time 3026ms
rtt min/avg/max/mdev = 15.872/19.820/25.003/3.367 ms
6. linux:~ # traceroute -n www.bucks.edu
traceroute to www.bucks.edu (192.231.233.6),
1 155.247.107.1
2.469 ms
2.336 ms
2 155.247.4.1
32.380 ms
31.799 ms
3 155.247.119.226 32.213 ms
32.263 ms
4 4.25.94.49
18.467 ms
18.293 ms
5 64.159.3.29
18.478 ms
12.350 ms
...
12 38.112.5.30
17.077 ms
17.709 ms
13 207.103.5.101
14.883 ms
17.671 ms
14 207.103.5.222
15.299 ms
15.814 ms
15 207.103.5.30
31.109 ms
76.618 ms
16 207.103.210.203 29.076 ms
38.247 ms
17 * * *
18 * * *
time=18.1
time=20.2
time=15.8
time=25.0
ms
ms
ms
ms
30 hops max, 40 byte packets
2.732 ms
31.181 ms
19.595 ms
18.317 ms
12.138 ms
13.827
16.511
19.462
67.554
59.058
ms
ms
ms
ms
ms
7. linux:/ # more /etc/services
# See: http://www.iana.org/assignments/port-numbers
echo
7/tcp
Echo
echo
7/udp
Echo
discard
9/tcp
Discard sink null
discard
9/udp
Discard sink null
daytime
13/tcp Daytime # Daytime (RFC 867)
daytime
13/udp Daytime # Daytime (RFC 867)
ftp-data
20/tcp
# File Transfer [Default Data]
ftp
21/tcp
# File Transfer [Control]
ssh
22/tcp
# SSH Remote Login Protocol
telnet
23/tcp
# Telnet
smtp
25/tcp mail
# Simple Mail Transfer
domain
53/tcp
# Domain Name Server
domain
53/udp
# Domain Name Server
http
80/tcp
# World Wide Web HTTP
epmap
135/tcp
# DCE endpoint resolution
netbios-ns
137/tcp
# NETBIOS Name Service
netbios-ssn
139/tcp
# NETBIOS Session Service
https
443/tcp
# http protocol over TLS/SSL
8. linux:/etc # more /etc/protocols
# See: http://www.iana.org/assignments/protocol-numbers
#
ip
0
IP
# internet protocol v4
icmp
1
ICMP
# internet control message protocol
#ip
4
IP
# internet protocol v4
tcp
6
TCP
# transmission control protocol
udp
17
UDP
# user datagram protocol
ipv6
41
IPv6
# IPv6