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158 Cards in this Set
- Front
- Back
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FHS
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(Filesystem Hierarchy Standard ) effort to standardize the file system in Linux see Sheet "FHS"
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mount point
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the directory to which the device/file system is mounted
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library
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collection of methods
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mount
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The command to mount a device/file system
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umount
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the command to unmount a device/file system
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fstab
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fstab, or file systems table, is a file in /etc/ that holds a table of all disks and partitions and shows how each are initialized
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mtab
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shows which file systems are mounted
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files
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files
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directories
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special files that are used to organize other files on the filesystem
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device files
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a file used to identify hardware devices such as hard disks and serial ports.
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links
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like a windows shortcut
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sockets
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Named pipes connecting processes on two different computers; they can also be represented by files on the filesystem
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FIFO
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(First In First Out) - named pipes- temporary connections that send information from one command or process in memory to another; they are also represented by files on the filesystem. Named pipes are called FIFO files.
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ls
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lists the contents of a directory (dir in windows terminal)
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cd
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Navigate to directories/"Change Directory" "cd ~" will take you to home cd .. will take you back a directory level cd / will take you to root
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pwd
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print working directory
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touch
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touch will create a file if it doesn't exist, it will be empty, if you touch an existing file it will updated the modifed date/time to now
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cat
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Command to view a file in the terminal short for concatenate, lets you combine files
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less
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show contents of a file, show one screen at a time, spacebar to scroll one page forward
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head
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front/top of a file first 10 lines
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tail
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tail will show the tail end of a file, the last ten lines
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mv
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Command to move a file/rename a file
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cp
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copies stuff
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mkdir
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makes directories
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rmdir
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removes a directory that is empty, use rm -r on directories that contain data (-r means recursive)
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rm
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remove a file (used with 'sudo' it can be very dangerous)
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ln
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make shortcuts/"link" -s for symbolic/soft
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KFind
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a graphical utility that may be used to find files and directories on the filesystem.
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find
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will search whole drive Table 5-19
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locate
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uses a database to keep track of the files and directories faster than find, does query instead of search, database needs to be updated to find latest stuff
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whereis
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will search binaries and man pages of source code to find a specific command
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which
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"which searches all paths listed in the variable PATH for the specified command and returns the full path of the command - It is especially useful if several versions of a command exist in different directories and you want to know which version is executed when entered without specifying a path
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type
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what kind of command is being executed: shell built in or a binary
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grep
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narrows a command to only find matches ps -A will show all running processes where ps -A | grep firefox will only show firefox processes (group regular expression pattern)
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regular expression
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definition of a language, pattern matching, crazy looking and almost impossible to memorize syntaxing Table 5-21
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ark
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" The program ark lets you collect multiple files or even entire directories into an archive for:
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tar
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not compression TapeArchive - tar is the most commonly used tool for data backup
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gzip
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compress files with - file compression
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gunzip
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decompress files with - file compression
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bzip2
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compress files with - file compression
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bunzip2
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decompress file with - file compression
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zcat
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view compressed files
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cpio
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copy into or out of an archive (1 file at a time) - used to archive files and directories
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rsync
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used to copy files and directories to a different location on the local computer or to a remote computer across a network
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dd
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used to copy files to an alternate location using a particular format or method
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mt
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magnetic tape command - used to manage tape devices
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cron
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a system service that can be used to run command on a repetitive schedule
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crontab
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used to schedule commands using the cron service
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shell
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"a program that serves as an interface between the user and the operating system - The shell accepts a user’s entries, interprets them, converts them to system calls, and delivers system messages back to the user, making it a command interpreter
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login shell
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" started when a user logs in to system
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non-login shells
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started from within a running shell
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history
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used to view and recall previously executed commands
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su
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enter super user/root mode, "su" doesn't execute your login script, "su - "does
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sux
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allow to run graphical operations
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id
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PID - is used identify processes (process ID)
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whoami
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returns and displays the current user
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exit
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logs you out of the terminal or root, depending where you are
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shell variable
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VARIABLE="whatever you want", if you use "export" it becomes a global variable
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environment variable
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is a global variable
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echo
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simply prints out everything after the word "echo"
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alias
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used to create special alias variables
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type
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used to determine the type of program for a command. The type command can be used to identify aliases and their target commands
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search patterns
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special characters that may be used to match multiple filenames. also known as wildcards
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piping
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These are the standard input or output for processes, tasks, and functions. The usual Input is the keyboard and the usual output for normal and error is the screen.
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redirection
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"This is when you change what the input is and where the output goes
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tee
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used to copy data from Standard Input to both Standard Output and a specified file.
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&&
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And operator
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||
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or operator
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vi
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complex text/file editor
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editors
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vi, nano, gedit, emacs
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sed
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used to search for and manipulate text
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awk
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used to search for and display text using a variety of different formatting options
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/etc/passwd
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User database, all information about a user except for passwords
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/etc/shadow
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Encrypted passwords of the users
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/etc/group
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Database of user groups
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pwconv
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To convert passwords to and from /etc/shadow, you can us the pwconv command. This command will also resolve discrepancies where an entry exists in /etc/passwd but not in /etc/shadow
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pwuconv
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To remove /etc/shadow and convert your user accounts to /etc/passwd only, use the pwunconv command
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useradd
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add the user (it's useradd not adduser)
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usermod
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Modify the user
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userdel
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delete the user
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groupadd
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add a group
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groupmod
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Modify the group
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groupdel
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delete a group
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ulimit
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" Prevents individual users from using system resources excessively at expense of other users
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chmod
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change the file/directory permissions
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chown
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change owner, to change the user and group affiliation of a file
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chgrp
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change group
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umask
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to modify(restrict) default access mode settings
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disk quota
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limit amount of disk space that a user can use
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quotacheck
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(initialize the quota system) checks the partitions with the quota keywords and stores the determined values in the files aquota. user and aquota. group
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edquota
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to edit the current quota settings for a user or group (used to specify quota limits for users and groups
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insserv
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install a service at a particular level (deamon to run in a run level) -install service
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file systems
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ext2,3,4,fat16,fat32,ntfs journaling vs non-journaling (metadata)
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fdisk
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program to manage file systems
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mkfs
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create file system
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fsck
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file system check and repair
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rpm
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used to install, remove, and find information on RPM software packages
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make
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used to compile source code into programs according to a makefile
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makefile
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a file created by a configuration script that contains settings used when compiling source code
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GRUB
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(Grand Unified Boot Loader) a bootloader for linux/unix, the default boot manager in SLES
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LILO
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(Linux Loader) another bootloader for linux/unix, the traditional boot manager used on Linux systems
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process
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"is used to execute an instance of a program
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daemon
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background jobs or services
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pid
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the Process Identification Number, can be used to reference a specific process when wanting to "kill" it
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job
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shows what jobs are showing, if you use the & to run a process then they will be a job.
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KDE System Guard
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A graphical utility that may be used to view and control processes
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ps
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use to see running processes
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top
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displays processes ordered by CPU usage by default, it also displays general info about processes running
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bg
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" move a process to the backround
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fg
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brings process to the foreground
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kill
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ends a process
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killall
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ends processes by name
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nice
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assign a priority(only root can speed up the process)
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runlevel
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" this is the mode that the operating system will run at for example
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init
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the system is initialized by /sbin/init, it becomes the parent of all of the user processes. It is the first process that runs outside of the kernel
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/etc/inittab
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" this is the configuration file for /sbin/init
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scripts
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scripts are used to start services
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cron
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The system service that executes commands regularly in the future based on information in crontabs
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at
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used to schedule commands to run at a certain time in the future
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process
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"A program in execution
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process elements
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" Identifier
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PCB
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Process Control Block (PCB) contains the process elements, created and managed by the operating system, allows support for multiple processes
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state?
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according to the history, mathew deleted these
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queue
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a waiting list, enter at the rear and leave at the front
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two state model
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" Process may be in one of two states
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five state model
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"-Running: Ready to execute
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context switch
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every time the processor goes down to a different process queue
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scheduling
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Timeout (timeslice), Interrupts (invoke interrupt handler), I/O request (schedule a new process because i/o is slow, Completion (when completes, we schedule another job)
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response time
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keep at adequate level while getting an optimal amount of work done
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throughput
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try to get the most work done in a second or hour(unit time period)
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efficiency
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Keep the processor busy, if you spend money on a good processor you want it to use the most
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priorities
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The story of Solitaire and the nuclear processor, some processes are just more important so it is good to have an algorithm that handles this. The command "nice" lets you specify how to run a process
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starvation
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Not getting enough processing time or enough cycles, priority schemes solve this (well good one should solve this)
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preemptive
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" Currently running process may be interrupted and moves to the ready state by the OS.
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FCFS
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"First-Come-First-Served
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round robin
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executes next process in the cycle, just follows the queue and gives each process a time slice
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SPN
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Shortest Process Next - we select the shortest because getting the shortest one out of the way we get more room for larger processes
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SRT
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Shortest Remaining Time
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HRRN
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Highest Response Ratio Next -
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feedback
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fair-share
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memory management
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" Subdividing memory to accommadate multiple processes
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relocation
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"-Programmer does not know where the program will be placed in memory
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protection
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" if you have ten processes running, they should not affect each other, it should act as if that is the only processes running
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sharing
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" Allow several processes to access the same portion of memory
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fixed partitioning
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if all partitions are full, the OS can swap a process out of a partition, any process whose size is less than or equal to the partition size can be loaded into an available partition
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internal fragmentation
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dynamic partitioning
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partitions are of variable length and number and are allocated to the size that the process needs
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external fragmentation
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placement algorithm
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will load in memory to the closes amount of space. If the process needs 3MB and there are two 6MB partitions left and a 4MB partiotion, it will put it in the 4MB because it is closer to 3MB.
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base register
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Starting address for the process
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bounds register
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Ending location of the process
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paging
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We divide up all physical memory into frames
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page
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frame
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sections within memory which load pages
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page table
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address resolution
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the long binary math thing
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Journaling file Systems
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Keeps metadata (data about data) about data
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