INFX 450 Final

Libre Office, gedit, terminal, writer, sheets

Home folder, filesystem, network shares

Encryption & Keys, Printer spool, terminal, user preferences

concatenates multiple files and displays the results on screen. Displays a text file

change directory to a specified path

Resolve a DNS entry to its IP address

List files and folders in a directory path

change the password for a specified user

shows the current working directory

shows the name of the OS that is running

shows all users logged on to the current terminal session

Shows the current logged on user

Ls –l sofa*

Ls –l *.txt

Ls –l *.from.*

Outputs one command as input to another command. Useful for showing how many search results are found. Ex: find . –name *.txt | wc –l

Redirects output to a file instead of the terminal window. Useful for logging purposes. Ex: ls –l > file1.txt > - create file, overwrite if exists. >> - create file, append if exists

Chmod

• U – Owner Permissions
• G – Group Permissions
• O – World Permissions

• Chmod u+r, u+w, u-x, g+r, g-w, g-x, o-r, o-w, o-x /home/foxr/text3.txt
• Chmod u=rw, g=r, o= text3.txt /home/foxr/text3.txt
• Chmod 640 /home/foxr/text3.txt

Ls –l /home/foxr/text3.txt

Find all files starting with user starting in /usr/sbin

Find all files starting in the user’s home directory that were accessed more recently than ~/DUMMY-DIRECTORY/file1.txt

Find all files starting in the user’s home directory that are larger than 100 bytes and smaller than 200 bytes

remove a file

Resolve a DNS entry to an IP address

Change the password for a specified user

move a file/directory from one place to another

shows the name of the OS that is running

Process ID. Unique number given to a process. ID’s are sequential

Priority. The importance each process is given to the system. High priority = high importance.

Nicesness. How “nice” a process is in relation to other processes. More nice = lower priority.

Amount of CPU a process is using

Amount of RAM a process is using

Niceness refers to how willing a process is in letting others use its resources. A high nice value means the process is willing to give other processes priority over it, meaning the process has a high priority. A low niceness means the process is “greedy” and has a high priority not willing to share its resources.

• Start the find process with a niceness of -15 and run in the background
• Will find all files starting in the user’s home directory that end in .txt and will go through each subdirectory. The results are stored in found_files.

• Start myscript process with a niceness of 15 and run it in the background
• Will run a script passing in the contents of inputfile and storing the output of the script in outputfile.

Reassign a nice value of 5 to the process whos PID is 18311. Run in foreground.

Reassign a nice value of 19 to all processes owned by the users foxr and zappaf

Reassign a nice value of -10 to the processes that have PID’s of 23813, 24113, and 26729

Vi file or :o file

:w filename

:q

• Regular expressions are search patterns that can be used to find strings that match a given expression. Generally, they will match the first part of the string that contains the pattern, even if there are multiple occurrences.
• Ex: ^[0-9]{5} will find all string that begin with at least 5 numbers [[:space:]][A-Z]{2}[[:space]][0-9]{5}$ will find all strings that contain a space, followed by 2 capital letters, followed by another space, followed by 5 numbers and ends the string. ^IL^60004

show what shell we are using

Display the message and store the user input into X, Y, and Z

If the value stored in X is greater than the value stored in Y

Then do

If the value stored in X is greater than the value stored in Z

Then assign Largest to be the value stored in X

Then assign Largest to be the value stored in Z

End the indented if block

Else if the value stored in Y is greater than the value stored in Z

Then assign Largest to be the value stored in Y

Else assign Largest to be the value stored in Z

End the large if block

will change the password of username. If no name is specified, root’s password will be changed.

group that belongs only to the user that created it

comment

Specify the home directory of the new account

Expiration date of the new account

list of supplementary groups of the new account

login shell of the new account

Don’t create home directory

alter defaults (no parameters displays defaults)

–g GID

Useradd –m –c “Suzie Creamcheese” –s /bin/tcsh creamcheeses

Useradd –m –c “Eric Cartman” –G cit371,informatics –u 1001 cartmane

–r deletes everything

shows all user accounts

shows all info about groups

shows hashed password info

shows password info

maximum number of days between password change

number of days of warning before password expires

Password expiration date

inactivity period (account will be locked after password has expired if it hasn’t been changed in this time)

change the password of username

lock user account

unlock user account

are stored in /etc/login.defs

change defaults (no parameters show defaults)

modifies the sudo command

Lets username run a specified command on machine (usually localhost)

reports disk file space usage (in 1K blocks)

shows all

shows the size of partitions in human-readable context (GB, MB, TB, etc.)

shows 1K blocks total, used, and available

Shows number of inodes that are used by each filesystem

shows mounted devices at boot time

shows what is currently mounted

read/write

read only

stores temporary files, stored in RAM

virtual file system that stores info about kernel subsystems, hardware devices, and device driver files

provides an interface to terminal devices

change to runlevel1

unmounts directory

will mount device as mountpoint

will mount /dev/sda5 as /home/

will mount all partitions specified in /etc/fstab

shows information about a file or files

will show the file mount point

allows you to specify codes

print filename

human readable format

inode number

file type

total size in bytes

time of last change since epoch

hard links

turns on swap space

stats

all

disable all swap spaces

used to store files needed to boot system

name of Linux kernel executable

bootloader for Linux

• directory for running processes by PID
• cmdline tells you path the process is located, can be called/accessed
• key-users: users that are able to use the process

used by both sys admins and users

primary directory of executable commands on the system

used when installing software locally. Protected from being overwritten during system updates/installs

controls activities of world-writable directories

in the world permissions

Useful for ensuring users cannot accidentally erase other user’s work in a shared folder

will create a new tar file called name consisting of everything in path

will display table of contents of name

automatic compression

shows all messages captured during bootup

data written to cache every time a change occurs, but only written to memory under certain conditions or specified intervals

memory cannot be stored for future use

Direct Memory Access: Allows certain hardware systems to access RAM independently of CPU

Interrupt Request: Hardware signal sent to CPU that temporarily stops a running program and allows interrupt handler to run instead

Plug and Play

• special tempfs image used in initram. Init will overwrite rootfs with mounted / file system
• Mounted physically at /dev/sda1

responsible for establishing user environment after hardware has been initialized and file system mounted

startup script

start the machine using the specified runlevel value

halt (Do NOT set initdefault to this)

single user mode

multiuser, without NFS (same as 3, if you do not have networking)

full multiuser mode

unused

X11

reboot (Do NOT set initdefault to this)

initializes system functions

• For I in /etc/rc$runlevel.d/K*
• for I in /etc/rc$runlevel.d/S*

• variable for runlevel value
• processes are executed(K)/stopped(S) at their respective runlevels

shows which runlevel a service is running

will turn off servicename

will turn off runlevel2 for sshd

will turn on runlevel5 for httpd

Automatically Start

Automatically Stop

• name – name of service
• status – particular action
• start – start the service
• stop – stop the service
• restart – restart the service
• status – show the status of the service

cron uses anacrontab

processes run daily

processes run weekly

processes run monthly

Specifies parameters of variables that are used when running

parameters that are passed when running

• 2345 – default run levels for the service
• 11,88 – S(stop,11) and K(run,88) symbolic links. Order which service will be started and stopped in the respective runlevels

system logger, logs activity to log files

configuration file for rsyslog daemon

specify all daemon activity should be logged

activity should be logged here

Ethernet address

loopback address

scripts for network service

shuts down network interface

shuts down eth0, lo still works

shuts down all network communication

brings up network interface

configuration file for eth0

DHCP or STATIC depending on addressing

specify whether interface starts on boot time

MAC address of hardware interface

configuration file for lo

IP Address

subnet mask

gateway address

network broadcast address

• DNS zone name file
• machine will look here for name servers

modifies localhost name server

shows IP routing table

shows entire local routing table

flushes entire local routing table

shows computer’s ARP address

address computer sends to gateway

shows ARP address

removes ARP address for ipaddr

firewall rule file (/etc/sysconfig/iptables)

specifies whether rules are saved when service is stopped or not

shows line numbers in output or not

• append rule to a rule chain
• INPUT – incoming traffic
• OUTPUT – outgoing traffic
• FORWARD – port forwarding

• allows rules to match based on connection state
•     --state
•               ESTABLISHED – connection is already established
•               RELATED – connection is new, but related to another connection already permitted
•                NEW – connection has not yet been seen
•                 INVALID – Traffic could not be identified

• Jump to specified target
• ACCEPT – accept packet and stop processing rules in current chain
• REJECT- reject packet and notify sender, stop processing rules in current chain
• DROP – silently ignore packet (don’t notify sender), stop processing
• LOG – Log packet, continue processing