Useful Linux Commands for the Lab

9/07/2017 - Optimized for Firefox 55.0.3

COPYRIGHT 1992 thru 2017 - David R. Woodsmall

cd = change directory chmod = change access modes on files (and directories) cp = copy files clear = clear screen df = show disk space dmsg = A FreeBSD command to peruse the contents of the System Message Buffer that have accumulated since the last reboot. Use to debug boot problems - typically: dmsgq | less du = show disk usage env = show environmental variables ethtool = Display or change ethernet card settings find = find . / -name "filename.suffix" -print > /find-output.log grep = filters out or in, specified strings - usually used with the pipe "|". ls -alF | grep -i myfile ifconfig = manage Network Intraces (list IP addr, etc) info = GNUs version of the man pages for GNU software - can be extensive. info ls insmod ModuleName = install loadable kernel module kill -9 pid# = kills the specified process (usually) ls -alF = lists all files in the working directory (the PWD) lsmod = List loaded modules lspci = Lists hardware using the PCI bus lspcmia = Lists devices using the PCMIA bus lsusb = Lists USB devices man command-name = displays info about specfied command; use q to exit. mkdir mkfs = make file system modinfo = does what it sounds like modprobe modprobe -r ModuleName = (Same as rmmod ModuleName) mount = ps -ef = List all running processes. ps -ef | grep -i myprocess pwd = list the directory in which you are currently working reboot = rmmode = removes the specified module or modules ssh = secure shell to remote host su = become superuser or some other user ("su dave") tee = Simultaneously store output in file and send to screen uname -a = list Host Name, OS, version and other info useradd = users userdel = usermod = view = invokes vi in read-only mode; use to read ASCII files. whereis = shows what path contains the module (if the module's DIR is in your path) that you would be executing. If you have 3 different versions of the same command in you path, whereis shows you which one will be executed. whoami = whom are you logged in as

Special Parameters & Options

nohup = Start a background job that will continue after you logout/disconnect & - run in the background, if the first character of the command | = pipe - used to feed output of one command into another command


Linux's directory structure - / /boot/ - Linux keeps information that it needs when booting up /bin/ /dev/ /etc/ - The configuration files for the Linux system. Most of these files are text files /home/ - This is where users keep their personal files. Every user has their own directory under /home, and usually it's the only place where normal users are allowed to write files. /lib/ - The shared libraries for programs that are dynamically linked. The shared libraries are similar to DLL's on Windows. /lost+found/ - /mnt/ - This directory is used for mount points. The different physical storage devices (like the hard disk drives, floppies, CD-ROM's) must be attached to some directory in the file system tree before they can be accessed. /proc/ - This is a special directory. Well, actually /proc is just a virtual directory, because it doesn't exist at all! It contains some info about the kernel itself. There's a bunch of numbered entries that correspond to all processes running on the system, and there are also named entries that permit access to the current configuration of the system. Many of these entries can be viewed. /root/ - The superuser's (root's) home directory. /sbin/ - Most system administration programs are stored in these directories. In many cases you must run these programs as the root user. /tmp/ - /usr/ - This directory contains user applications and a variety of other things for them, like their source codes, and pictures, docs, or config files they use. /usr is the largest directory on a Linux system, and some people like to have it on a separate partition. /usr/doc/ - Documentation for the user apps, in many file formats. /usr/include/ - Header files for the C compiler. /usr/local/ - This is where you install apps and other files for use on the local machine (only) If you find interesting apps that aren't officially a part of your distro, you should install them in /usr/local. /usr/sbin/ - Most system administration programs are stored in these directories. In many cases you must run these programs as the root user. /usr/share/ - Config files and graphics for many user apps /usr/src/ - Source code files for the system's software, including the Linux kernel. /usr/X11R6 - The X Window System and things for it. The subdirectories under /usr/X11R6 may contain some X related stuff - dics, headers, configs,... /var/ - This directory contains variable data that changes constantly when the system is running /var/log/ - A directory that contains system log files /var/mail/ - Incoming and outgoing mail is stored in this directory /var/spool/ - This directory holds files that are queued for some process, like printing


/etc/default/useradd - /etc/fstab - This file contains descriptive information about the various file systems and their mount points. /etc/inittab - A text file that describes what processes are started at system bootup and during normal operation. /etc/passwd - /etc/exports - permantly exports specified files to other systems - can set permissions


dig - dig (domain information groper) is a flexible tool for interrogating DNS name servers. It performs DNS lookups and displays the answers that are returned. dig(1) - Linux man page Check your DNS records with dig - nslookup - online web tool to lookup and find IP address information in the DNS (Domain Name System) nslookup -


1. Install new disk hardware 2. partition the new disk 3. Create the file systems on the new disk 4. Mount the file systems See also Linux(click here) UNIX / LINUX AND VARIANTS