FOR 302 REVIEW
Things to know for the CS 302 final exam


Users
	How do I add a user?
		sudo adduser name

	What information is in /etc/passwd, /etc/shadow, /etc/group and /etc/gshadow
		/etc/passwd -> no actual passwords. Name, NumericId, home dir (where it puts you on login), shell (bash) info saved here
		/etc/shadow -> where encrypted password actually is. Takes first 2 char of username and uses that as salt for hash

	What is a userid?
		numeric id for individual

	userid = 0 means what?
		root

Permissions
	How to read the output of 'ls -l'.
		first 3->user, then group, then other

	What permissions do I need to read/write/execute/delete
		RWX - delete is permissions on directory above
		r -> read
		w -> write
		x -> execute

	How do I change permissions
		chmod

Crontab
	crontab -e -- edits the crontab

	crontab -l -- lists the crontab

	crontab --help 

	Can you do something like "Every tuesday at 3:12am"
		yes-> m,h,dom,mon,dow -> 12, 03, *, *, 02
		(dow is days of week. Sunday is both 0 and 7. Mon-Sat is 1-6)

	Can you do "every hour"
		yes -> 0, *, *, *, *

	Who runs as?
		cron of user. Root has their own, but will run as user

Apache
	What is documentroot?  Where is it set?
		/etc/apache2/mods-enabled/000-default.conf
		
	If I try and access http://me.nmu.edu/~fred, which files will it look for?
		userdir for fred- likely pub folder

	Where are the log files?
		/var/log/apache2

	What is the difference between mods-available and mods-enabled
		mods-available don't fuck with, things COULD include. mods-enabled is what we have

	The <Directory ..> thing.
		for files in <Directory [whatever path]>, apply these things		

	find vs grep
		find looks for filenames, grep looks for contents

	Who does apache run as?
		www-data for security reasons- NOT root

	alias?
		alias [URL] [FILEPATH TO THING]
		example: alias /secret /home/carchris/pub/mysecrets.html		

Email
	SMTP vs POP vs IMAP
		smtp -> push giving you email, sending it
		pop/imap -> pull, what email do you have for me		

	What is mydestinations?
		Hostnames for people I will recieve and store email for

	Config file?
		/etc/postfix/main.cf		

	How do I make an alias?  What's the file, and what's the command?
		/etc/aliases -> sudo aliases name:whereitgoes		

	How do I make a .forward?  Where does it go?
		go to the persons home dir, file is .forward, contents are: where it should go, world readable, not world writable		

	Where are the log files?
		/var/log/mail.log

	What is relay access denied
		you sent me email, not my destinations, not relaying it for you

	How do we block spam
		black lists/block lists
			no mail from these places
		baynsian analysis
			words and phrases of email
		features of the email header
			from the future, something is stupid/misformatted

Command Line
	How do i find out if a service is running.
		sudo service [whatever] status
		sudo service [whatever] stop -> stops service
		sudo service [whatever] start -> starts service
		sudo service [whatever] restart -> restarts service
		(synonyms for systemctl)

	How do I find a file given it's filename? (find command)
		find -name filename /path/youre/looking/in (can use *)

	How do I find a file given some text within the file (grep command)
		grep whatever /path/youre/looking/in
		grep -i whatever /path/youre/looking/in	(-i is ignorecase)	

	Redirection of outputs/errors?
		2> /redirects/errors/here
		> /redirects/output/here

	What is /dev/null and how do I throw away errors?
		DevNull is the abyss
		2> /dev/null

	What are the filename matching wildcards.
		* - zero or more character
		? - one character
		[0-9] - one character in a range

	Piping:  What does "ls | wc -l" do?  How many programs run?
		ls lists all files. The | gives that output to wc -l, which counts the # of lines outputted

	Executables/file redirection?
		both sides are executables for |
		> or < is a file redirection, left hand side is ALWAYS executable

	Given the output of 'ls -l' who can read/write/delete a file?
		the first 3 letters of the output are the permissions of the user, 2nd 3 are the permissions of the group, last 3 are others
				

 
Shell Scripting
->->->	NOTE: I found a helpful page at:
	https://www.oreilly.com/library/view/learning-the-bash/1565923472/ch01s09.html
	(it contains some special characters and such to review)

	What does #!/bin/bash do?
		Means give text of this to /bin/bash, which knows how to execute

	How do I run a command and put the results in a variable (backtics)
		let B=`[command]`
		(or) B=`[command]`

	How do for loops and while loops and if statements work? (the [] are important for the while and if statements)
		for loop:

			for variable in list/file/whatever/1 2 3 4 .. N
			do
				stuff/code
			done

		while loop:

			while [ condition ]
			do
				stuff/code
			done

		if statement:

			if [ condition ]
			then
				stuff/code
			fi
			
	Know how cut works.
		cut -c 3-12 -> cuts a line by characters, only 3-12 will remain

	Know what backtics ` do
		d=`date` -> d becomes the output of the executable. ` surrounds commands

	For loops in shell (i.e. for i in /home/*)
		Same as for loops above. For i in /home/* it will do the thing for every file in /home/*

	What is $1 and $2?
		first and second arguments of a command. Example: "kill me slowly" -> kill is the command. Me is $1, slowly is $2

Samba
	Config file?
		/etc/samba/smb.conf

	How do I make a share named after a user?
		make a [homes] section in /etc/samba/smb.conf		

	How do I set someone's password?
		sudo smbpasswd -a (adds passwd for first time, setting a password not first time no -a)

	How do I delete their account?
		sudo smbpasswd -x

	How do I make a share not named after a user?
		make a section in /etc/samba/smb.conf (the thing with the [])

	How do I make a share read only?
		include "Read Only = yes" in the share directory [bracket thing]

NFS
	What infomation is in /etc/fstab?
		stuff that happens on bootup/reboot

	What infomation is in /etc/exports?
		/home [ip](rw, [jibberish]) <- basically starts a "share" saying if [ip] wants to access, they can in read/write mode

	How do I mount one time only by hand (the mount command)
		sudo mount server:/offer /where

The Cloud
	About how much does it cost to have a cloud computer
		very very cheap

	What are some advantages
		(cheap, great connectivity, reliable, no labor for setup, etc)

	What are some disadvantages
		(not on local wire, secrecy etc)
	
	Does anyone run servers on bare metal (not vm) in 2021?
		(Yes, but the trend is strongly towards fewer)

Apt-get
	install
		install this thing
	delete
		blow away, but leave config files
	purge
		delete EVERYTHING