CSI 135

1. CSI 135 Review of Networking & Systems Administration

2. Quick Review Unix networking

3. Networking & Systems Administration • Since we ran through last week’s presentations at lightning speed (excuse the visual pun), this presentation will highlight those topics that you should know for the final

4. Networking • The command for viewing network information (network interfaces, IP addresses and such) on a Unix system is ifconfig. It is similar to the ipconfig command on a Windows system.

5. ifconfig • Ifconfig • Ifconfig –a • Ifconfig eth0

6. ifconfig yes?> ifconfig eth0 eth0 Link encap:EthernetHWaddr 00:16:35:69:BD:79 inet addr:192.168.0.6 Bcast:192.168.0.255 Mask:255.255.255.0 inet6 addr: fe80::216:35ff:fe69:bd79/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:121875451 errors:0 dropped:0 overruns:0 frame:0 TX packets:122824442 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:125311644 (119.5 MiB) TX bytes:3819007610 (3.5 GiB) Interrupt:209 Memory:fdef0000-fdf00000

7. ifconfig yes?> ifconfig eth0 eth0 Link encap:EthernetHWaddr 00:16:35:69:BD:79 inet addr:192.168.0.6 Bcast:192.168.0.255 Mask:255.255.255.0 inet6 addr: fe80::216:35ff:fe69:bd79/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:121875451 errors:0 dropped:0 overruns:0 frame:0 TX packets:122824442 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:125311644 (119.5 MiB) TX bytes:3819007610 (3.5 GiB) Interrupt:209 Memory:fdef0000-fdf00000 IP address

8. IPv4 vs IPv6 • There are two versions of TCP/IP currently in use – IPv4 and IPv6 • There are roughly 4 ¼ billion IP addresses available in IPv4 • There are roughly 4 ¼ billion * 4 ¼ billion * 4 ¼ billion * 4 ¼ billion addresses in IPv6 • The reason for going to IPv6 is that the address space in IPv4 is inadequate

9. Public & Private IP Addresses • 10.x.x.x is a private address • 192.168.x.x is a private address Each x can be anything

10. DNS • DNS is a widely distributed global lookup service that allows us to look up IP addresses for systems when we know their fully qualified domain names (e.g., www.aacc.edu)

11. DNS • To resolve (i.e., translate) a fully qualified domain name into an IP address, you can use the nslookup command

12. DNS $ nslookup vader.aacc.edu Server: cns.inflow.pa.bo.comcast.net Address: 68.87.64.150 Non-authoritative answer: Name: vader.aacc.edu Addresses: 136.160.248.28, 66.240.14.28 If we’re on campus, we will see: Name: vader.aacc.edu Address: 192.168.0.6

13. traceroute • The traceroute command shows you the path a connection takes to get to a remote system • yes?> traceroute www.google.com • traceroute to www.google.com (72.14.204.147), 30 hops max, 40 byte packets • 1 * * * • 2 gig0-8.umcp-core.net.ums.edu (136.160.255.33) 2.551 ms 2.556 ms 2.540 ms • 3 te3-3--276.tr01-asbnva01.transitrail.net (137.164.131.109) 4.384 ms 4.372 ms 4.478 ms

14. ping • ping is troubleshooting command that sends a small request to a remote system that requests a reply • When you get replies back, you know: • You can reach the remote system • Your network connection is good • The remote system is up • How long it takes to reach the remote system

15. top • The top command shows you how busy a system is and which processes are consuming the most of the CPU • Tasks: 182 total, 1 running, 181 sleeping, 0 stopped, 0 zombie • Cpu(s): 0.2%us, 0.6%sy, 0.0%ni, 99.0%id, 0.2%wa, 0.0%hi, 0.0%si, 0.0%st • Mem: 2075384k total, 1943324k used, 132060k free, 396308k buffers • Swap: 4192956k total, 428k used, 4192528k free, 1223228k cached • PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND • 23128 shs 15 0 2420 968 708 R 2.0 0.0 0:00.01 top • 1 root 15 0 2156 584 508 S 0.0 0.0 0:06.42 init • 2 root RT -5 0 0 0 S 0.0 0.0 2:33.41 migration/0

16. Unix Commands • telnet • ftp • ssh • scp Remote login

17. Unix Commands • telnet • ftp • ssh • scp File transfer

18. Quick Review Unix Systems Administration

19. SysAdmin Tasks • Installing the operating system • Installing applications and patches • Setting up user accounts • Monitoring disk space • Monitoring performance and faults • Rebooting as needed

20. SysAdmin Commands • Superusers can kill any process, change permissions (or remove) any file

21. su • The su (switch user) command allows you to switch accounts (i.e., become another user) • You need to know the other user’s password to use this command – unless you are logged in as the superuser

22. sudo • The sudo command allows a regular (non-root) user to run certain commands with superuser privilege • The specific commands that can be run with sudo need to be configured by the system administrator

23. superusers • Systems administrators generally log into a Unix system using their personal accounts and switch to superuser (root) when they need to run a command that requires privileged access • superuser = root

24. Other Unix Commands • tar (tape archive) – creates an archive containing a selection of files, good for backing up files or moving a collection of files to a different system

25. Other Unix Commands • crontab – used to set up “cron jobs”, i.e., jobs that run according to a configured schedule such as every Tuesday at 2 PM

26. Other Unix Commands • crontab – used to set up “cron jobs”, i.e., jobs that run according to a configured schedule such as every Tuesday at 2 PM 0 14 ** 2 /home/jdoe/bin/backup 2>&1 /dev/null Tuesday Script or command to be run 0 minutes Any month Of year Throw output away 2 PM Any day Of month