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Linux+ LX0-102

Comptia Linux+ Exam 2

QuestionAnswer
What is the purpose of /etc/profile or /etc/bash.bashrc? These files are used to set environment configurations for all users. Eg: alises set here are set for all users
What is the purpose of the env command? Without options: list set environment variables (set by itself shows shell variables). Can also be used to run a command/script using specific(different) environment.
What command is used to make a variable an environment variable, and what does that mean? export VARIABLE="value" will make VARIABLE usable in all shells, not just the current shell.
What is the purpose of the set command? Sets various options that affect the user environment.
How does the -a option function on the set command? export variables that are defined, basically works like an export command
How does the -f option function on the set command? disable globbing (like using * for all filenames)
How does the -o option function on the set command? This option is used for many sub options ie: ingoreeof = don't exit shell on ctrl-d, markdirs = give trailing / to directories, noclobber = prevent > from truncating existing files, nounset = treats unset parameters as an error (-u also does this)
How does the -v option function on the set command? print shell input lines as they are red (good for debugging)
How does the -x option function on the set command? print command and their arguments as they are executed (good for debugging)
What command is used to delete an environment variable? unset <ENV VARIABLE>
What is the difference between .bash_profile, .bash_login and .profile files in users home directory? All are environment configurations read by "login" shells, often set to simply read .bashrc, Bash checks for these files in order and uses the first that exists and is readable.
What is the purpose of .bashrc? Users individual environment configuration is stored here, it is run by interactive shells which are non-login
What is the purpose of .bash_logout? Performs whatever is inside the script after the logout command is issued
What is the purpose of .bash_history? Contains commands that the user has typed into the shell. Can set how many commands can be stored in .bashrc normally
What is the purpose of a function? Funny sounding question! Function is part of a script that performs a sub-task and can be called by other parts of the script. Eg: myfn() {; commands; };
What is the purpose of the alias command? Can put in long options to commands to always use them or make a shorter/different command name to use a command. Eg: alias ls='ls --color=auto'
What is the purpose of lists in scripting? Not really sure but it MIGHT be the && and || operators...
What is the syntax of a FOR loop? for <variable> in <set of variable, or some kind of test>; do
What is the syntax of a WHILE loop? while <test statement>; do; <something>; done; This loop will continue while the test statement remains TRUE, until is the same syntax but will loop while the statement remains FALSE.
What is the purpose of the test command? It runs a test and will come back either true or false, commonly used in loops and scripts.
What is the value of true and false using a test command? 0 = true, 1 = false
What kind of test is this? [ 4 -lt 5 ]? Is 4 LESS THAN 5?
What kind of test is this? [ 4 -gt 5 ]? Is 4 GREATER THAN 5?
What kind of test is this? [ 4 -le 5 ]? Is 4 LESS THAN OR EQUAL TO 5?
What kind of test is this? [ 4 -ge 5 ]? Is 4 EQUAL TO OR GREATER THAN 5?
What kind of test is this? [ 4 -eq 5 ]? Is 4 EQUAL TO 5?
What kind of test is this? [ 4 -ne 5 ]? Is 4 NOT EQUAL TO 5?
What kind of test is this? [ 'abc' == 'cba' ]? Is 'abc' the same string as 'cba'?
What kind of test is this? [ 'abc' != 'cba' ]? Is 'abc' a different string than 'cba'?
What kind of test is this? [ -n "$string" ]? Is $string a non empty string?
What kind of test is this? [ -z "$string" ]? Is $string an empty string?
What kind of test is this? [ -d filename ]? Is filename a directory?
What kind of test is this? [ -e filename ]? Does filename exist?
What kind of test is this? [ -f filename ]? Is filename a regular file?
What kind of test is this? [ -r filename ]? Is filename readable? Can also test -w or -x for other file permissions.
What is the syntax of an IF statement? if [ some kind of test ]; then; do something; fi; Can also use elif and else statements to continue the if statement.
How can you terminate a loop? break
How can you terminate a script? exit
How can you get user input into a script? read <var1> <var2>; this waits for user input to be entered, ended by enter key (new line)
What is the output of this command? seq 10 Numbers from 1 to 10, one number per line
What is the output of this command? seq 1 10 Numbers from 1 to 10, one number per line
What is the output of this command? seq 1 2 10 Number 1, 3, 5, 7, 9, one number per line. Basically it counts from the first number to the last number in increments of the middle number. seq 1 10 10 would only output the number 1.
What is the shebang line? What is it's purpose? Shebang is #! followed usually with /bin/sh in a script. It is found at the beginning of the script and it used to indicate what is used to interpret it.
How can you use command substitution? 2 ways: $(command) or `command`. The second method uses BACKTICKS not quotes.
How can you use math expressions? 2 ways: $((expression)) or let variable= expression
What is the command to make a new database in SQL? CREATE DATABASE <name>;
What is the command to make a new table in SQL? CREATE TABLE <tablename> (fieldname fieldtype, 2ndname 2ndtype, etc...); Eg: CREATE TABLE employees (id int(5), name varchar(50));
What is the command to work on a specific database in SQL? USE <databasename>;
What is the command to delete a database in SQL? DROP DATABASE <databasename>;
What command is used to get general table information in SQL? DESCRIBE <tablename>;
What is the command to add new data (rows) into a table in SQL? INSERT INTO <table> (fieldname, fieldname,...etc) VALUES (value1, value2,...etc);
What is the command to edit data (rows) of a table in SQL? UPDATE <table> SET field1=value1, field2=value2,...etc WHERE field#=value;
What is the command to view data of a table in SQL? SELECT <field1, field2, etc || *> FROM <table> WHERE <field> IS NOT NULL; The WHERE command here is optional to only gather some data of the table.
What is the command remove data (rows) from a table in SQL? DELETE FROM <table> WHERE <field>=<value> AND <field2>=<value2>;
What is the command to sort data of a table in SQL? SELECT *(or specific fields) FROM <table> ORDER BY <field> <ordertype>; <ordertype> can be asc=ascending, desc=descending and others.
What is the command to sort data of a table into groups in SQL? SELECT *(or specific fields) FROM <table> GROUP BY <field to group by>; For example this could be used to group people who are born in the same month together.
What is the command to join data from 2 tables in SQL? SELECT table1.field1, table1.field2, table2.field1 AS <newfieldname> FROM table1,table2 WHERE table1.field1 = table2.field2; This would make a table with 3 fields (1 from table 2 + 2 from table 1), the AS statement changes the title of one of the fields
What is an INNER JOIN in SQL? SELECT * FROM <table1> INNER JOIN <table2> ON <table1.field> = <table2.field>; INNER JOIN produces only records that match in tables selected.
What is an FULL [OUTER] JOIN in SQL? SELECT * FROM <table1> FULL JOIN <table2> ON <table1.field> = <table2.field>; All records are shown joining matching sets where available.
What is an LEFT [OUTER] JOIN in SQL? SELECT * FROM <table1> LEFT JOIN <table2> ON <table1.field> = <table2.field>; Left (first) table all data shown, right (second) table only matched data shown.
What is an CROSS JOIN in SQL? SELECT * FROM <table1> CROSS JOIN <table2>; || SELECT * FROM <table1>, <table2>; no filter, joins every row from 1st table to every row from 2nd (makes a long table!).
What is contained in the file /etc/X11/xorg.conf? Sets up desktop gui, Device= video card; Monitor= refresh, resolution, etc; Screen= order of monitors (layout); Module= drivers for hardware; ServerLayout= links all other sections together; InputDevice= mouse + keyboard;
What command is used to run remote X window commands on a local system? Why isn't it used anymore? xhost <+|-><hostname|IP>; this gives permission (or take away) for people to use this feature. Not used since not encrypted, SSH tunneling used instead.
What environment variable needs to be set to allow a remote computer to use X window? DISPLAY=<IP of remote>:<display#>; Eg: export DISPLAY=192.168.1.2:1.0
What command is used to get technical info on a specific window display? xwininfo; type command and then click on a window with mouse to get info if used without options.
What command can be used to get info on current display, like X version, resolution, colour depth? xdpyinfo
What command is used to generate a default Xorg config file? X (or xorg) -config
What option in a xorg.conf file would set the font server? FontPath "unix/:-1"
What is the difference between Bitmap and Outline fonts? BITMAP can have scaling problems, OUTLINE scales easily but might look ugly!
How does the /etc/inittab affect your GUI? It sets the default runlevel; id:#:initdefault: ... #=5 would make gui login
What is the xdm config file? (full path) /etc/X11/xdm/xdm-config
Where do you set the greeting for xdm? (full path) /etc/X11/xdm/Xresources ; xlogin*greeting is for the greeting message
What file controls access for remote login to xdm? (full path) /etc/X11/Xaccess
What is the kdm config file? /usr/share/kde4/config/kdm/kdmrc || /etc/X11/kdm || /etc/kde/dem ; this depends on the distribution; uses "[sections]" like rsync config
How can you configure xdm to allow remote sessions? Edit /etc/X11/xdm/xdm-config ; change DisplayManager.requestPort: 0 ; 0 changes to 177
How can you configure kdm to allow remote sessions? Edit the config file (depends on the distro) and [xdmcp] Enable=True
How can you configure gdm to allow remote sessions? Edit the config file /etc/gdm/custom.conf ; [xdmcp] Enable=True
What is the gdm config file? (full path) /etc/gdm/custom.conf ; uses "[sections]" like rsync config
What are Sticky Keys? Allows using key combination (ctrl+alt+delete) by pressing keys one at a time instead of simultaneously
What are Repeat Keys? Change the delay required before multiple keystrokes are logged when holding down a key
What are Slow Keys? Allows setting a delay for how long a key is held down before it is detected at all. Helps prevent keys pressed accidentally or more than once in quick succession.
What are Bounce Keys? Only a single key stroke logged when a key held down, after set time a second keystroke registers.
What are Toggle Keys? Sound alert gets played when CAPS LOCK or NUM LOCK are activated
What are Mouse Keys? Control the mouse with the arrow keys from a keyboard.
What is a screen reader and which ones are generally available to use? Reads out the text that appears on screen. Orca and Emacspeak are examples.
What is Orca, what is it capable of? Orca is an Accessibility feature in Linux, performs screen reading, braille display, magnifier
What is an On-Screen Keyboard? Example? Keyboard displays on screen to be used with a mouse instead, GOK is a popular example.
What are Gestures? Moving the mouse in different ways can perform actions like double clicking, right click, etc.
What is the syntax used in the file /etc/passwd? usernam : password : uid : gid : comment : homedir : startupshell
What does an x mean in the password field of the /etc/passwd file? Password is stored in the /etc/shadow file which is more secure.
What does an * mean in the password field of the /etc/passwd file? The account is locked
What can you change the startupshell field in the /etc/passwd file to lock an account? Set it to /bin/false or /sbin/nologin ; nologin is nicer in that it displays a message indicating the account is inaccessible so is preferred.
What does ! mark mean in the /etc/shadow file? ! in password field means none set, ! at the beginning means its a locked account.
Where does Linux store group information, and what is the syntax? /etc/group is the file and the syntax is groupname:password:gid:
What directory functions as a template for new users? /etc/skel
What command is used to modify passwd settings like min days for password change, maximum inactivity, etc? chage; passwd and usermod are also able to do many of the same things
What does the -E option do when used with chage? Set date for password to expire
What does the -I option do when used with chage? Set number of days of inactivity after password expire before locking account
What does the -m option do when used with chage? Set minimum number of days before password can be changed
What does the -M option do when used with chage? Set maximum number of days password is valid
Which command is used to make a new group? groupadd
Which command is used to delete a group? groupdel
Which command is used to edit a group? groupmod
What does the -g option do for both groupadd and groupmod? Set the GID
What does the -r option do for groupadd? Make the group a system GID (less than 500 or 1000 depending on the system)
What does the -f option do for groupadd? Force
What does the -o option do for groupmod? Allows 2 groups to share the same GID, must be used with -g
What does the -n option do for groupmod? Names a New Name, Nice!
Which command is used to create a new user? useradd
What does the -c option do for useradd? Set the comment field
What does the -d option do for useradd? Set the user home directory, must be used with the -m option
What does the -e option do for useradd? Set the expiration date (temp account)
What does the -p option do for useradd? Sets the password (must be pre-encrypted)
What does the -M option do for useradd? DOES NOT set a home directory for the user
What does the -m option do for useradd? Creates a home directory for the user (normally defaults to this)
What does the -G option do for useradd? Define secondary groups for the user
What does the -g option do for useradd? Sets the primary group for the user (normally is the same as the username)
What does the -f option do for useradd? Sets number of days after the password expires that the account remains unlocked so user can log in an change password (-l disables feature and is default)
What does the -k option do for useradd? Set to use a different template directory instead of /etc/skel ; requires the -m option to function
What does the -f option do for userdel? Force deletion of the user EVEN IF THEY ARE LOGGED ON! not good practice should kick them first before you kill them...
What does the -r option do for userdel? Remove user home directory and mail spool, not default since there might be data there that should be retained.
What does the -d option do for usermod? Change the user home DIRECTORY!
What does the -e option do for usermod? Set EXPIRE date on the user
What does the -f option do for usermod? Set number of days after account expired until permanently disabled...not sure why f...
What does the -g option do for usermod? Set the GROUP id/name of the users new default login group
What does the -G option do for usermod? Set the secondary GROUPS the user is a member of
What does the -l option do for usermod? Change the LOGIN name of the user
What does the -L option do for usermod? LOCK the account, -U = UNLOCK
Where would you store a script that you wanted to run once a day? /etc/cron.daily ; There are also directories for hourly monthly and weekly
What is the purpose of the /etc/cron.d/ directory? Stores any crontabs (not scripts) that use any timing you like to run as system crontab, more organized that putting everything into one large crontab
As a system administrator how would you grant or stop a user from accessing the at daemon? /etc/at.deny and /etc/at.allow files; one username per line; at.allow has priority and if neither files exist only root may use daemon. If only at.deny exists and it's empty everyone is allowed to use.
As a system administrator how would you grant or stop a user from accessing the cron daemon? /etc/cron.deny and /etc/cron.allow files; one username per line; cron.allow has priority and if neither files exist only root may use daemon.If only cron.deny exists and it's empty everyone is allowed to use.
Where is the system crontab file stored? What is normally inside of this file by default? /etc/crontab ; normally contains the commands to run the scripts in the /etc/cron.* directories.
Where are the cron configurations files and the root conrtab file stored? /var/spool/cron/*
What does the -u option do when used with crontab command? Open up a specified USERS crontab
What does the -e option do when used with crontab command? EDIT your crontab file
What does the -l option do when used with crontab command? LIST your crontab file
What does the -r option do when used with crontab command? REMOVE your crontab file
How would you get crontab command to read a file instead of editing it manually? crontab <filename>
What does the -f option do when used with the at command? Reads from a FILE instead of prompt.
What formats does the at command accept for the time argument? HH:MM; MMDDYY; MM/DD/YY; DD.MM.YY; Aug 16; Aug 16 2014; +2 hours
When the at command is reading from the prompt how do you indicate the end of commands to run? ctrl-d ; EOF
What command is used to list pending at jobs? atq
What command is used to remove pending at jobs? atrm <job #>
What are the fields used for time in a crontab? (syntax) Minuteofhour(0-59) Hourofday(0-23) Dayofmonth(1-31) Monthofyear(1-12) Dayofweek(0-7)
If a cron job has a */40 in the minutes field and * in the rest, when will it be run? It will run at the 0th and 40th minute of every hour. You would think */40 means every 40 mintues but this command only works properly for times that divide into 60 nicely. So this will have a 40 then 20 minute delay repeated.
If a cron job has a 0-10 in the minutes field and * in the rest, when will it be run? How many times will it run in an hour? It will run once a minute from the 0th minute to the 10th minute, so it will run 11 times in an hour.
If you want a cron job to run on only Monday and Thursday, what would you place into the dayofweek field? 1,4
What is the purpose of using >/dev/null 2>&1 in a cron job? This will disable the e-mail notification that crontab normally sends. Sends it to /dev/null instead.
If you wanted to run a cron job once a day, what is an alternate format that you can use instead of the 5 fields? @daily ; options for @hourly, @monthly and @yearly exist as well
What is the main file that Linux uses to check which timezone it is using? /etc/localtime ; Often (and best practice) this will be a symbolic link to the timezone file in /usr/share/zoneinfo
What is contained in the /etc/timezone file? Text based file showing which timezone one resides: Eg. America/New_York
How can you check which timezone is currently set on a system? Use the date command, it will show the three letter timezone code currently being used.
Where are the various timezone files stored? /usr/share/zoneinfo
What is the purpose of the LC_ALL environment variable? If it is set it will override all other LC_* variables. Good for a temporary change.
What is the purpose of the LANG environment variable? It sets the locale in case the LC_* variables aren't set, like a fallback. If LANG=C there is no translation done by programs which is good for debugging.
What is the purpose of the TZ environment variable? This allows changing the timezone of specific users which you can set in their login scripts (remote user from another timezone). export TZ=:/usr/share/zoneinfo/America/Boston
What is the purpose of tzselect? CLI tool to help make time zone changes, ask for location in several steps
What is the purpose of tzconfig? GUI(ish) tool to help make time zone changes, ask for location in several steps
What syntax is used to set the date using the date command? DDMMhhmmYYYY (M=Month, m=minute)
What command is used to convert the encoding of a text file? iconv -f <fromcode> -t <tocode> ; --list will list all possible encondings
What is ASCII? Oldest most primitive encoding method, many non English punctuations and symbols not supported so not very good for international use. 7-bit encoding in an 8-bit (byte)
What is ISO-8859? Early attempt to extent ASCII, uses the 8th unused bit for extra characters. Broken into sub-standards to cover specific areas; Eg: ISO-8859-1 = western europe
What is UTF-8? Variable (1-4 byte encoding) extensions. Enables encoding of ANY language supported by Unicode.
What is Unicode? Character set designed to support as many languages as possible.
How can you list the current locale settings on a machine? locale command without additional arguments lists locale settings
What is the format (syntax) of a locale setting? language_TERRITORY.CODESET ; Eg: en_US.UTF-8
What does the -a option do to the locale command? Displays ALL the locales available to use on a system
What does the -m option do to the locale command? list of all character MAPPINGS (maybe -c would have been a better choice for this, alas, --charmaps also does this!)
Where is the config file for NTP? (full path) /etc/ntp.conf
What option inside of the NTP config file dictates which servers to use? server <hostname or IP> ; normally will have more than 1 server configured and NTP will try to use the best ; /etc/ntp.conf
What does the --hctosys (or -s) option do when used with hwclock command? Hardware Clock will set the SYStem time, normally will be used with either --localtime or --utc to specify timezone
What does the --systohc (or -w) option do when used with hwclock command? SYStem time will set the Hardware Clock, normally will be used with either --localtime or --utc to specify timezone
What does the -r (or --show) option do when used with hwclock command? Displays hardware clock time in local time
What does the --set option do when used with hwclock command? Sets the hwclock, can also use --date=<newdate> in DDMMhhmmYYYY format
What command is used to monitor the status of the NTP daemon? ntpq ; -p will print the list of peers and a summary of their state
What does it mean when the NTP daemon changes time by SLEWING it? Small time difference between system and NTP server time (less than 0.5 seconds), it will adjust time less often
What does it mean when the NTP daemon changes time by STEPPING it? The time difference is large between the local computer and remote server (between 0.5 seconds and 17 minutes), adjusts time more frequently.
What does it mean to have INSANE time? There is a greater than 17 minute difference between local and NTP server time, NTP will poll other server to get time and ignore insane time.
What does the -q option do when used with the ntpd command? Basically mimics the ntpdate command which is supposed to be retired soon
What command can be used to refresh system time with NTP servers? ntpdate <server>; this will sync local time to the servers time.
What does pool.ntp.org represent? Pool of ntp servers, when you use it you will be given one of many possible servers. Can get a different server in pool every time you launch ntp.
Where is the system logging configuration file located? (full path) /etc/syslog.conf
What is the syntax of the syslog.conf? facility.priority action ; commonly the action is the file to send the logs to but other options exist
In syslog.conf what does this line represent? *.=crit -/var/log/whatevs All facilities will send ONLY their critical priority messages to /var/log/whatevs using some kind of write-buffers (the -)
In syslog.conf what does this line represent? mail,daemon.!crit @logger.domain.com The mail and daemon facilities will send their messages of LOWER priority than critical to a remote machine logger.domain.com
What is the purpose of klogd? Manages logging KERNEL messages.
Which command is used to send messages into various log files? logger
What does the -s option do to the logger command? Sends ouput to STANDARD ERROR & the log file
What does the -p option do to the logger command? Sets the PRIORITY of the log
What does the -t option do to the logger command? Changes the TAG of the log; default tag is: logger
How does a user set up mail forwarding? pur username for local redirect or an entire e-mail address to send elsewhere in the ~/.forward file
Where are mail aliases set? /etc/aliases
What is the syntax for the /etc/aliases file? name: /dir/file OR |command OR :include:/dir/file (file of names) OR name@domain.com (full e-mail)
What command is used to compile the /etc/aliases file? newaliases
What is the syntax to send a mail? mail [options] to-address ; If reading message from prompt finish mail with a "."
What does the -s option do to the mail command? Sets the SUBJECT of the mail
What does the -c option do to the mail command? Sets the CC address of mail
What does the -b option do to the mail command? Sets the BCC address of mail
What does the -f option do to the mail command? Read mail...f?
What does the -u option do to the mail command? Check specified USERS mail
What command is used to show mail that is in queue to being sent? mailq
Which mail program was designed as a modular replacement to sendmail, uses multiple programs to handle small tasks. postfix
Which mail program is non modular like sendmail, but easier to configure exim
Which mail program is design with security as a major goal. qmail
Where does user mail get stored? /var/spool/mail
How do you connect to the GUI CUPS configuration? localhost:631 in a web browser
Where is the cups configuration file located? (full path) /etc/cups/cupsd.conf
In the CUPS config file how do you set local printing? Allow [from] 127.0.0.1
In the CUPS config file how do you set printing for a specific subnet? Allow [from] 192.168.1.0/24
In the CUPS config file how do you set printing from local subnets? Allow [from] @LOCAL
What is the difference between Order Deny,Allow or Order Allow,Deny in CUPS config? Deny first means default is deny unless in allow statement, Allow first means default is allow unless in deny statement
Where are the CUPS printer definitions set? (full path) /etc/cups/printers.conf ; easier to use the web based GUI
What older (legacy) system was used for printing before CUPS? lpd
What command is used to send a file to print? lpr [options] file
What does the -P option set for lpr? Sets the destination PRINTER
What does the -# option set for lpr? Set the NUMBER(#) of copies to print
What does the -r option set for lpr? REMOVE the file after printing
What does the -m option set for lpr? Send MAIL to specified username when job is completed
What command is used to remove a print job from a specified printer? Lprm -P<print> <job#>
What command can you use to see the print jobs in queue and get their job #s? lpq ; -P<printer> to check a specific printer
What command is used to start stop and reorder the queue of jobs? lpc ; cupsenable, cupsdisable and lpmove are also able to control the print queue.
What file is used to map port numbers to names? (full path) /etc/services
What command is used as a simple replacement for nslookup? host
What is the -c option used for with the ping command? Allows you to set the COUNT of pings to use instead of going until a ctrl-c is issued
What command is used to get information on the owner of a FQDN? whois
How can you use dig to check for an MX record? dig domain.com MX
What does the -n option do with the traceroute command? Uses IP address instead of performing hostname lookup, can save a lot of time.
What is the difference between the tracepath and traceroute commands? tracepath has output for each test packet, so longer output but fewer options than traceroute
What does IPv6 use instead of ARP? NDP ; Neighbour Discovery Protocol
What does '::' mean in an IPv6 address? This is placed between the largest set of quad 0s ; can only do it once in an address since more than once and you can't tell how many quad 0s go where.
What are the private IPv6 addresses? fec, fed, fee, fef
What are the link local IPv6 addresses? fe8, fe9, fea, feb...what a giant waste for link local...
What service is port#: 20 associated with? FTP Data
What service is port#: 21 associated with? FTP Control
What service is port#: 22 associated with? SSH
What service is port#: 23 associated with? Telnet
What service is port#: 25 associated with? SMTP
What service is port#: 53 associated with? DNS
What service is port#: 80 associated with? HTTP
What service is port#: 110 associated with? POP3
What service is port#: 119 associated with? NTTP(Network News Transfer Protocol)
What service is port#: 139 associated with? NetBIOS Sessions (SAMBA)
What service is port#: 143 associated with? IMAP
What service is port#: 161 associated with? SNMP (UDP)
What service is port#: 443 associated with? HTTPS; HTTP over SSL
What service is port#: 465 associated with? SMTP over SSL; or URL Rendezvous Directory (URD)
What service is port#: 993 associated with? IMAP over SSL
What service is port#: 995 associated with? POP3 over SSL
What file do many distros look at for hostname setting? (full path) /etc/hostname ; some use /etc/sysconfig/network
What file is used to associate hostnames to IP addresses locally? (full path) /etc/hosts
What file stores the DNS server information? (full path) /etc/resolv.conf
What file configures which method of hostname resolution to use, and in which order? (full path) /etc/nsswitch.conf
What file uses this syntax: 192.168.7.23 host.domain.com? /etc/hosts
What file uses this syntax: nameserver 192.168.7.23? /etc/resolv.conf
What file uses this syntax: hosts: files dns? /etc/nsswitch.conf
What command and syntax is used to configure interface eth0 with an IP of 192.168.2.2/24? ifconfig eth0 192.168.2.2 netmask 255.255.255.0 broadcast 192.168.2.255
What commands can be used to bring an interface up/down? ifup/ifdown interface; ifconfig interface up/down
What command and syntax is used to add a default gateway of 192.168.26.1? route add default gw 192.168.26.1
What command and syntax is used to set all packets addressed to 192.168.3.0/24 network to use the gateway 192.168.3.1? route add -net 192.168.3.0 netmask 255.255.255.0 gw 192.168.3.1
If you want to set up your linux machine up as a router (forwarding packets) what file must you edit and what has to be in it? /proc/sys/net/ipv4/ip_forward ; it has to have "1" inside to allow ip forwarding.
What command is used to temporarily change a hostname on a machine? hostname
What does the -t option do when used with the netstat command? Display TCP ports
What does the -u option do when used with the netstat command? Display UDP ports
What does the -p option do when used with the netstat command? Give the PROGRAM name
What does the -a option do when used with the netstat command? Display ALL ports (Established is default, show listening ports as well)
What does the -n option do when used with the netstat command? Display NUMERICAL IP instead of hostnames (no DNS lookup)
What does the -i option do when used with the netstat command? Display INTERFACE INFORMATION, somewhat similar to IFCONFIG command
What does the -r option do when used with the netstat command? Display the ROUTING info similar to ROUTE command
What command is used as a packet sniffer (intercepts and logs network packets)? tcpdump
What does the -c option do when used with the tcpdump command? Stop after a certain COUNT of packets (#).
What does the -D option do when used with the tcpdump command? Lists interface that tcpdump can listen on
What does the -w option do when used with the tcpdump command? WRITE to file instead of screen.
What command would you use to find files owned by root with their SUID/SGID/both set? SUID= find / -uid 0 -perm +4000; SGID= find / -uid 0 -perm +2000; BOTH= find / -uid 0 -perm +6000;
Which command is used to display open files and who is accessing them (including over network)? lsof
What does the -i option do when used with the lsof command? Shows all types of open files, you can refine the output with arguments like ipv4/6, tcp/udp, ip/hostname, :service/port(s)
Which command is used to scan for open ports on local or remote computers? nmap
What does the -sT command do when used with nmap? Check for open TCP ports
What does the -sU command do when used with nmap? Check for open UDP ports
What file is used to configure users who are allowed to use the sudo command? (full path) /etc/sudoers
How do you edit who can get sudo privileges? visudo
What is the syntax used to give a user/group root sudo privilege? username OR %groupname ALL= (ALL) ALL
How do aliases work in the /etc/sudoers file? You can set an alias such as Cmnd_Alias STORAGE=/sbin/fdisk, /sbin/sfdisk, /sbin/parted; And then do username ALL= STORAGE; which allows that user to use those commands set in alias.
What types of aliases can be made in /etc/sudoers? User_Alias (group users together), Runas_Alias (runs commands as a user), Host_Alias (group hostnames or IP networks), Cmnd_Alias (group commands)
Which command is used to change user? su = switch user
What does the - option do when used with the su command? Log onto user using their environment
What does the -c option do when used with the su command? Run a single command as the user (like sudo for root)
What command is used to limit the resources that users are allowed? ulimit
What does the -H option do when used with the ulimit command? Sets it to a HARD limit
What does the -S option do when used with the ulimit command? Sets it to a SOFT limit
What are the various resources that ulimit can control? memory (stack, rss, data, virtual), size (core, fsize), processes (nproc, cpu)
What does the -a option do when used with the ulimit command? Reports on the current settings
What is the configuration file for pam_limits? (full path) /etc/security/limits.conf
What is the syntax for the pam_limits config file /etc/security/limits.conf? domain type item value ; domain = user OR @group OR * ; type = hard OR soft OR - ; item = core, data, cpu,etc. ; value = ##s
What are the various resources that can be controlled by the /etc/security/limits.conf file? memory (stack, rss, data), size (core, fsize), processes (nproc, cpu, priority), files (nofile=# of open files), logins (maxlogins)
What file if it exists will only allow root to log into system and for all other users simply show the file contents? /etc/nologin
What is the inetd config file? (full path) /etc/inetd.conf
What is the syntax of the inetd config file /etc/inetd.conf? service stream|dgram tcp|udp wait|nowait root|guest|nobody /usr/bin/tcpd in.servicedaemon (Eg: tftpd)
What is contained in the folder /etc/inetd.d/? Configurations for specific services will generally reside here instead of in inetd.conf, makes it more manageable
What is tcpd and how does it work? Also called TCP wrappers. Adds security through access control and logging. Uses the hosts.allow and hosts.deny files to determine access rights.
How does inetd provide any security? inetd will utilize the tcpd (tcp wrappers)
How do the /etc/hosts.allow and /etc/hosts.deny files function? hosts.allow takes precedence so if it exists name MUST be in it to get access, if neither exists only root is allowed.
What is the syntax of the /etc/hosts.allow and /etc/hosts.deny files? daemon-list: client-list ; Eg: vsftpd:192.168.7. EXCEPT 192.168.7.105
What is the config file for xinetd? (full path) /etc/xinetd.conf
What is the difference in syntax between xinetd and inetd? inetd has one long line to configure a server, xinetd break it up into individual options; ie: socket_type = stream; protocol = tcp; wait = no; user = root; server = /usr/sbin/in.ftpd;
How does xinetd provide security? does NOT use tcp wrappers like inetd, has security build in. bind = set to specific interface; only_from = like hosts.allow; no_access = like hosts.deny; access_times = when users allowed to log in (does not kick though)
Where are individual server config files stored for xinetd? (full path) /etc/xinetd.d/*
What is the config file for ssh server? (full path) /etc/ssh/sshd_config
What is the config file for ssh client? (full path) /etc/ssh/ssh_config
What option in the ssh server config is used to allow/disallow root to log in? PermitRootLogin yes/no
What option in the ssh server config is used to allow/disallow tunneling for X? X11Forwarding yes/no
What is the difference between sshv1 and sshv2? sshv1 is compromised and should no longer be used. sshv2 is secure still.
Does ssh encrypt the data or the password exchange? ssh encrypts both data and password exchange
What is the syntax to connect to an ssh server called sshserver.domain.com as the user BLBrian? ssh BLBrian@sshserver.domain.com
What command is used to generate RSA and DSA keys? ssh-keygen
What is the purpose of the ssh-agent command? Tool used to remember passwords so you only need to type it once per local session. USAGE: ssh-agent /bin/bash
What is the command used to add private keys to be managed by ssh-agent? ssh-add. Eg: ssh-add ~/.ssh/id_rsa ; after command it will prompt to type the passphrase
Where are user RSA and DSA keys stored? PRIVATE: ~/.ssh/id_rsa + ~/.ssh/id_dsa ; PUBLIC: ~/.ssh/id_rsa.pub + ~/.ssh/id_dsa.pub
Where are the server RSA and DSA keys stored? /etc/ssh/ssh_host_rsa(OR dsa)_key and ssh_host_rsa(OR dsa)_key.pub
How can you set it up so that users can log in without the need for password using an rsa key? Place public keys (id_rsa.pub type) in ~/.ssh/authorized_keys to authenticate users without the need for password
Where would an admin place public keys of hosts that they trust? /etc/ssh_known_hosts
Where do the public keys of remote servers get stored when a user logs into them? ~/.ssh/known_hosts
What command can be used to encrypt and sign e-mail messages? gpg (GNU Privacy Guard)
Where do keys get stored that are created by gpg? ~/.gnupg/
What is the command option to create a key using gpg? --gen-key
What is the command option to list the keys on keyring using gpg? --list-keys
What is the purpose of the --export option when using gpg? This is used to put your public key to a file to share with others.
What is the difference between the --sign and --clearsign options when using gpg? sign = encrypt entire message, makes .gpg file; clearsign = only adds an encrypted signature so people can verify it came from you, makes a .asc file
What does the --verify option do when used with gpg? This is used to check if a signature on a received file is proper.
What option in /etc/ssh/sshd_config is used to allow for port tunneling? AllowTcpForwarding yes/no
What does the -L option do when using ssh to port tunnel in this command? ssh –L 142:stuff.alcatel.com:143 BLBrian@meme.reddit.com which port to listen to (local port 142 to port 143 on alcatel.com)
With xdm what is the process of files used to set up the display? Xsetup - sets up login screen >> Xstartup - after user logs in >> Xsessions >> Xreset - when the user ends the session to restart the cycle
In what file is the GDM greeting set up? /etc/gdm/custom.conf
What does the --edit-key option do when used with gpg? Presents a menu which enables you to perform key-related tasks
What file must exist for the last command to function? /var/log/wtmp
What command is used to help configure CUPS? lpadmin
What is the LPD queue directory? (full path) /var/spool/lpd
What command is used to store passwords from the /etc/passwd file to the /etc/shadow file? pwconv
What is the purpose of the /var/run/utmp file? Allows you to see who is logged in using the who command
What command is used to check your gid and uid? id
How many bits in an ipv6 address? 128
How many bits in an ipv6 address are for host bits? 64
What command is used to delete the default gateway? route del default gw
Created by: Datheral