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Linux Operating System test 2
Terms for test 2
136
Computer Networking
Undergraduate 3
11/08/2011

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Term
FHS- File Hierarchy System
Definition
specifies which directories must be located on the first level after the root directory and what they contain.
Term
Mount Point
Definition
the point where you mount a filesystem; for temp purposes use /mnt directory otherwise make an appropriately named directory.
Term
Library
Definition
/lib directory contains the libraries used by programs in the directories /bin; and /sbin; Kernal modules located in /lib/modules
Term
Mount
Definition
[ mount dev/hd1 /data ] (will be mounted into /data directory)
Term
fstab
Definition
defines how storage devices and partitions are to be mounted and integrated into the overall system
Term
m tab
Definition
handles the mounted devices and is automatically updated by the mount command.
Term
device files
Definition
each piece os hardware is represented by this.
Term
links
Definition
references to files located at other points in the file system
Term
sockets
Definition
a special file with which data exchange between two locally running processes can be implemented through the file system.
Term
FIFO
Definition
(first in first out OR named pipe): files used to exchange data between processes, one direction of exchange only.
Term
Touch
Definition
creates a file; type [touch bob] creates a file named bob
Term
/cat
Definition
shows contents of a file
Term
/head
Definition
shows first 10 lines of a file
Term
/tail
Definition
shows bottom 10 lines of a file
Term
/mv
Definition
move a file from one directory to another or rename it [mv /home/myfile /home/yourfile] changes name of file to yourfile and keeps it in the same directory /home
Term
/cp
Definition
copy a file from one directory to another
Term
/mkdir
Definition
create a directory
Term
/rmdir
Definition
remove a directory [IF ITS EMPTY]
Term
/rm-r
Definition
removes ENTIRE DIRECTORY
Term
/rm
Definition
remove a file
Term
/ln
Definition
create a link
Term
KFind
Definition
used to find files with specific features
Term
/find
Definition
locate files that meet some criteria [find /--name examplename] looks through file names not content.
Term
/locate
Definition
alternative to [find] command
Term
/whereis
Definition
shows the location
Term
/which
Definition
shows the first result
Term
type
Definition
what type of file or command when the command is entered, tells you if it is in the shell or it tells you what directory it is in.
Term
grep
Definition
searches through contents of files, where the [find] command only looks through file names.
Term
Regular Expression
Definition
special metacharacters used to match patterns of text within text files; communly used by text tool commands such as grep.
Term
ark
Definition
lets you collect multiple files or even entire directories into an archive
Term
tar
Definition
most commonly used tool for backup
Term
[zcat]
Definition
command used to view the contents of text files that have been compressed with gzip.
Term
[cpio]
Definition
used to make and access and archive, you can extract all of those files but just want one file, cpio can extract just this one file.
Term
[rsync]
Definition
used to copy files and directories to a different location on the local computer or to a remote computer across a network.
Term
[dd]
Definition
used to copy files to an alternate location using a particular format or method.
Term
[mt]
Definition
(magnetic tape) command used to manage tape devices
Term
shell
Definition
command interpreter
Term
login shell
Definition
default login shell stored in etc/password
Term
non-login shell
Definition
default login shell stored in etc/password
Term
history
Definition
keep track of how many commands default is 1000 commands, type history to see all or press up on keyboard. type !30 to execute command 30.
Term
/su
Definition
Switch user
Term
/sux
Definition
switch user allows you to run x server
Term
/id
Definition
shows username and ID
Term
PS1
Definition
changes prompt text
Term
shell variable
Definition
create a shell var by typing bob=echo hello ; only visible in current shell
Term
environment variable
Definition
visible in current shell and any sub shells you start
Term
echo
Definition
echoes back to the screen type [echo $bob] shows value of bob
Term
alias
Definition
create shortcuts to commands and their options; [alias hello='echo"hello $USER"'
Term
type [type command]
Definition
will tell you if its build into the shell or not
Term
search patterns
Definition
regular expression syntax, search for strings or patterns in files
Term
piping
Definition
symbol: [||]. send the output from one program to the input for another program
Term
redirection
Definition
symbol: [>]. sends the output from one program to a file, overwrites existing file can send to the printer [ ls > /dev/lp0 ]

symbol: [<]. gets input from a file and puts unto the program
Term
tee
Definition
takes one output and splits in two, into a file and to standard output (monitor)
Term
&& "AND"
Definition
Does first command ONLY. if successful, then it does command two.
Term
|| "xor"
Definition
if first command is successful don’t do second, if first FAILS, do second command.
Term
vi
Definition
text editor: You enter in command mode
press i to enter insert mode
esc to return to cmd mode
:q to quit without saving
:wq or :x to save and quit
Term
other editors?
Definition
vim, emacs, xmacs, joe, e3, pico
Term
sed
Definition
stream editor, lets you do non interactive editing on a file , replace every occurrence of bob with Robert.
Term
/awk
Definition
text manipulator, same action as sed
Term
/pwconv
Definition
converts the passwd file to the shadow file
Term
/pwuconv
Definition
remove etc/shadow and convert your user accounts to etc/passwd only
Term
usermod
Definition
modify charactictics of the user
Term
[groupmod]
Definition
allows you to modify a group 
Term
ulimit
Definition
lets you set limits on resources
Term
chmod
Definition
know chmod set permissions on the file what is the command
[chmod 6 4 0] UGR user group other
777 for directory and 666 for files
Term
chown
Definition
change file ownership [ chown new_user filename ] changes just owner, to change group as well in one command [ chown new_user.new_group filename ]
Term
chgrp
Definition
this command changes the group affiliation. only usable if the user IS THE OWNER and a MEMBER OF THE NEW GROUP.
Term
umask
Definition
type [umask 022] and it subtracts from the default, read means u can do ls to list contents, write means u can add and delete, and execute means you can cd into the directory.
Term
Disk Quota
Definition
start quota service [ quotaon ]
Hard Limits: Cannot be exceeded
Soft Limits: Can be exceeded TEMPORARILARY, grace period is set to 7 days.
Term
quotacheck
Definition
initialize the quota system
Term
edquota
Definition
edit current quote settings for a user or group [ edquota -u username ];
[ edquota -g groupname ]
Term
insserv
Definition
[ insserv scriptname ]; [ ln scriptname ]
Term
What are the File Systems?
Definition
Ext2 - uses e2fsck
Ext3
ReiserFS - [ mkreiserfs ]
JFS - developed by IBM for its AIX systems
XFS  - started by XFS
Term
fdisk
Definition
used for partitioning hard disks [ fdisk /dev/hdb ]
Term
mkfs
Definition
command to make file system; [ mkfs -t ext2 /dev/hdb1 ](specifies file type)
Term
fsck
Definition
[fsck filesystem] to check and repair file systems; defaults to checking filesystems in etc/fstab
Term
RPM
Definition
Redhat Package Manager; manages software packages on host
Term
make
Definition
used to compile multiple source files in the correct order;  can also use to install and uninstall the program to or from the right location on a hard disk.  
Term
GRUB
Definition
(startup prompt) Grand unified boot loader, give you option to select which kernel you want to boot.
Term
LILO
Definition
boot manager similar to GRUB
Term
daemon
Definition
a system process that is not associated with the terminal
Term
[jobs]
Definition
returns all processes that have been started from that shell and run in the background, each is assigned a job ID#
Term
KDE System Guard
Definition
shows you the processes running “Task Manager”
Term
KDE System Guard: [ps]
Definition
KDE System Guard: process status
Term
KDE System Guard: /top
Definition
KDE System Guard: shows how much computing time processes use
Term
KDE System Guard: /bg
Definition
KDE System Guard: moves a process to the background or type [ xeyes & ] to run in background
Term
KDE System Guard /fg
Definition
KDE System Guard: moves a process to the foreground
Term
Nice
Definition
change priority of a process
Term
[nice]: # does what?
Definition
sets priority of nice
Term
[renice]: does what
Definition
changes nice priority (only root can give a negative priority#)
Term
runlevel
Definition
to change runlevel type [ runlevel 5 ]
Term
runlevel -rc0
Definition
(runlevel) halt
Term
runlevel -rc1
Definition
(runlevel) single user
Term
runlevel -rc2
Definition
(runlevel) multi user no networks no graphics
Term
runlevel -rc3
Definition
(runlevel) multi user with networking no graphics
Term
runlevel -rc4
Definition
(runlevel) none?
Term
runlevel -rc5
Definition
(runlevel) multi user with networking and graphics [default boot runlevel]
Term
runlevel -rc6
Definition
(runlevel) reboot
Term
init
Definition
started by the kernal as the first process of the system, since it is the last process running, it ensures all other processes are correctly ended. CONTROLS BOOT UP AND SHUT DOWN
Term
/etc/inittab
Definition
configuration for init process, where you can control runlevels in the init environment
Term
Scripts
Definition
a predetermined reaction process
Term
/cron
Definition
used to schedule a REOCCURRING job; example: run a job Mon - Fri every 10 min etc
Term
/crontab
Definition
contains the cron schedule listing
Term
/at
Definition
used to schedule a ONE TIME job
Term
What are the 3 components of PROCESS?
Definition
Data | Code | State
Term
What are the Process Elements?
Definition
PID (process ID #)
Priority
PC (Program Counter)
Memory Pointers ( shows location of allocated memory)
I/O status info
Accounting Info (who is using the resources on the computer)
Term
PCB: Process Control Block
Definition
has all info needed to control your process, has PID, UID, GID, priority.
Term
P two state model
Definition
two states: running and not running
Term
P five state model
Definition
admit disptch rlease
New------>ready<-------->running->exit
| timeout |
| |
blocked<-----------|
Term
context switch
Definition
when one process has been executing, and we to to another process, timeout, I/o, termination, interrupt. we save the process status and registers, and select the next process and update status. PC always has the next process to fetch
Term
response time
Definition
the time it takes when a process is activated to when it executes
Term
throughput
Definition
how much work you get done in a given set of time ( work completed in a day )
Term
efficiency
Definition
how fast the scheduling is.
Term
priorities
Definition
Processes have different priorities (PID), The lower the PID the faster they run. there are multiple queues to represent each level of priority
Term
nonpreemptive
Definition
one process cannot be interrupted and can run forever, no timeout.
Term
preemptive
Definition
current process may be interrupted and moved to the ready state by the OS, allows for better service since one process cant monopolize the processor.
Term
FCFS (First Come First Serve)
Definition
each process joins the ready queue, and waits its turn, and next in line is executed in order. favors CPU bound processes
Term
Round robin
Definition
uses preemption based on a clock, assigns time slices to processes, Everyone gets a turn.
Term
SPN
Definition
SHORTEST PROCESS NEXT. nonpreemptive, process with the shortest expected processing time is selected next.
Term
SRT
Definition
Shortest remaining time.
Term
HRRN
Definition
Highest Response Ratio Next: choose next process with the greatest ratio
{ time spent waiting + expected service time / expected service time }
Term
Feedback
Definition
changes priority during execution and is moved to different queue line; penalize jobs that have been running longer.
Term
fair-share
Definition
Term
relocation
Definition
programmer does not know where the program will be placed in memory when it is executed. While in execution, may be swapped to disk and returned to memory at a different location.
Term
protection
Definition
processes should not be able to reference memory in another process without permission.
Term
sharing
Definition
allow several processes to access the same portion of memory
Term
fixed partitioning
Definition
any process whose size is less than or equal to the partition size can be loaded into an available partition.  If a partition is full, the OS can swap a process out of a partition.
Term
internal fragmentation
Definition
Occurs in Fixed Partitioning; already allocated, but has not been used, if my parttion is 10b and my program is 6 b there is wasted space, any program no matter how small occupies the entire partition.
Term
dynamic partitioning
Definition
process allocated exactly how much memory as is needed, eventually get holes in memory, called external fragmentation.
Term
external fragmentation
Definition
occurs in Dynamic Partitioning; have memory that is unallocated but is too small to be useful.
Term
base register
Definition
Starting address for the process {only exectues if offset + base <= bounds}
Term
bounds register
Definition
ending location of the process {only exectues if offset + base <= bounds}
Term
paging
Definition
divide memory and each process into equal size chunks called pages (process) and frames (memory)
Term
page fault
Definition
portion of a process, if you call a page and it's not in memory then you have a page fault it has to go look in Virtual memory, Occurs when you try to access something that is not in memory
Term
-u
Definition
changes the user id in [usermod]
Term
CPU
Definition
most expensive part of computer, determines efficiancy.
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