August 25, 2018

Collection of FreeBSD tips

FreeBSD text image

This is a collection of FreeBSD tips that comes with the fortune programe included in the system. Many of these will work on any Unix system.

Any user that is a member of the wheel group can use “su -” to simulate a root login. You can add a user to the wheel group by editing /etc/group.

By pressing “Scroll Lock” you can use the arrow keys to scroll backwardthrough the console output. Press “Scroll Lock” again to turn it off.

Can’t remember if you’ve installed a certain port or not? Try pkg info -x port_name.

Ever wonder what those numbers after command names were, as in cat(1)? It’s the section of the manual the man page is in. man man will tell you more.

Forget how to spell a word or a variation of a word? Uselook portion_of_word_you_know

Forget what directory you are in? Type pwd.

Forget when Easter is? Try ncal -e. If you need the date for Orthodox Easter, use ncal -o instead.

FreeBSD is started up by the program ‘init’. The first thing init does when starting multiuser mode (ie, starting the computer up for normal use) is to run the shell script /etc/rc. By reading /etc/rc and the /etc/rc.d/ scripts, you can learn a lot about how the system is put together, which again will make you more confident about what happens when you do something with it.

Handy bash(1) prompt: PS1="\u@\h \w \!$ "

Having trouble using fetch through a firewall? Try setting the environment variable FTP_PASSIVE_MODE to yes, and see fetch(3 for more details.

If other operating systems have damaged your Master Boot Record, you can reinstall it with boot0cfg(8). See man boot0cfg for details.

If you accidentally end up inside vi, you can quit it by pressing Escape, colon (:), q (q), bang (!) and pressing return.

If you are in the C shell and have just installed a new program, you won’t be able to run it unless you first type rehash.

If you do not want to get beeps in X11 (X Windows), you can turn them off with xset b off

If you have a CD-ROM drive in your machine, you can make the CD-ROM that is presently inserted available by typing mount /cdrom as root. The CD-ROM will be available under /cdrom/. Remember to do umount /cdrom before removing the CD-ROM (it will usually not be possible to remove the CD-ROM without doing this.)Note: This tip may not work in all configurations.

If you need a reminder to leave your terminal, type leave +hhmm where hhmm represents in how many hours and minutes you need to leave.

If you write part of a filename in tcsh, pressing TAB will show you the available choices when there is more than one, or complete the filename if there’s only one match.

If you set watch = (0 any any) in tcsh, you will be notified when someone logs in or out of your system.

If you use the C shell, add the following line to the .cshrc file in your home directory to prevent core files from being written to disk:limit coredumpsize 0

If you want df(1) and other commands to display disk sizes in kilobytes instead of 512-byte blocks, set BLOCKSIZE in your environment to ‘K’. You can also use ‘M’ for Megabytes or ‘G’ for Gigabytes. If you want df(1) to automatically select the best size then use df -h.

If you want to play CDs with FreeBSD, a utility for this is already included. Type cdcontrol then help to learn more. (You may need to set the CDROM environment variable in order to make cdcontrol want to start.)

If you’d like to keep track of applications in the FreeBSD ports tree, take alook at FreshPorts:

In order to make fetch (the FreeBSD downloading tool) ask for username/password when it encounters a password-protected web page, you can set the environment variable HTTP_AUTH to ‘basic:*’.

In order to search for a string in some files, use ‘grep’ like this:grep "string" filename1 [filename2 filename3 ...]This will print out the lines in the files that contain the string. grep can also do a lot more advanced searches - type man grep for details.

In order to support national characters for European languages in tools like less without creating other nationalisation aspects, set the environmentvariable LC_ALL to ’en_US.ISO8859-1’.

man firewall will give advice for building a FreeBSD firewall

man hier will explain the way FreeBSD filesystems are normally laid out.

Man pages are divided into section depending on topic. There are 9 differentsections numbered from 1 (General Commands) to 9 (Kernel Developer’s Manual).You can get an introduction to each topic by typing man <number> introIn other words, to get the intro to general commands, typeman 1 intro

man ports gives many useful hints about installing FreeBSD ports.

man security gives very good advice on how to tune the security of yourFreeBSD system.

man tuning gives some tips how to tune performance of your FreeBSD system.

Need to do a search in a manpage or in a file you’ve sent to a pager? Use /search_word. To repeat the same search, type n for next.

Need to find the location of a program? Use locate program_name.

Need to leave your terminal for a few minutes and don’t want to logout? Use lock -p. When you return, use your password as the key to unlock the terminal.

Need to print a manpage? Use: man name_of_manpage | col -bx | lpr

Need to quickly empty a file? Use : > filename.

Need to quickly return to your home directory? Type cd.

Need to remove all those ^M characters from a DOS file? Trytr -d \\r < dosfile > newfile

Need to see the calendar for this month? Simply type cal. To see the whole year, type cal -y.

Need to see which daemons are listening for connection requests? Use sockstat -4l for IPv4, and sockstat -l for IPv4 and IPv6.

Need to see your routing table? Type netstat -rn. The entry with the G flag is your gateway.

Nice bash prompt: PS1='(\[$(tput md)\]\t <\w>\[$(tput me)\]) $(echo $?) \$ '

Over quota? du -s * | sort -n will give you a sorted list of your directory sizes.

nc(1) (or netcat) is useful not only for redirecting input/output to TCP or UDP connections, but also for proxying them with inetd(8).

sh (the default Bourne shell in FreeBSD) supports command-line editing. Just set -o emacs or set -o vi to enable it.

Simple tcsh prompt: set prompt = '%# '

The default editor in FreeBSD is vi, which is efficient to use when you have learned it, but somewhat user-unfriendly. To use ee (an easier but less powerful editor) instead, set the environment variable EDITOR to /usr/bin/ee

Time to change your password? Type passwd and follow the prompts.

To change an environment variable in /bin/sh use:VARIABLE="value"``export VARIABLE

To change an environment variable in tcsh you use: setenv NAME "value" where NAME is the name of the variable and “value” its new value.

To clear the screen, use clear. To re-display your screen buffer, press the scroll lock key and use your page up button. When you’re finished, press the scroll lock key again to get your prompt back.

To determine whether a file is a text file, executable, or some other typeof file, usefile filename

To do a fast search for a file, trylocate filenamelocate uses a database that is updated every Saturday (assuming your computer is running FreeBSD at the time) to quickly find files based on name only.

To erase a line you’ve written at the command prompt, use Ctrl-U.

To find the hostname associated with an IP address, usedrill -x IP_address

To obtain a neat PostScript rendering of a manual page, use -t switch of the man(1) utility: man -t <topic>. For example:man -t grep > # Save the PostScript version to a fileorman -t printf | lp # Send the PostScript directly to printer

To quickly create an empty file, use touch filename.

To read a compressed file without having to first uncompress it, use zcat or zless to view it.

To repeat the last command in the C shell, type !!.

To save disk space in your home directory, compress files you rarely use with gzip filename.

To search for files that match a particular name, use find(1); for examplefind / -name "*GENERIC*" -lswill search ‘/’, and all subdirectories, for files with ‘GENERIC’ in the name.

To see all of the directories on your FreeBSD system, typefind / -type d | lessAll the files?find / -type f | less

To see how long it takes a command to run, type the word “time” before the command name.

To see how much disk space is left on your partitions, usedf -h

To see the 10 largest files on a directory or partition, usedu /partition_or_directory_name | sort -rn | head

To see the IP addresses currently set on your active interfaces, type ifconfig -u.

To see the last 10 lines of a long file, use “tail filename”. To see the first 10 lines, use head filename.

To see the last time that you logged in, use lastlogin.

To see the MAC addresses of the NICs on your system, typeifconfig -a

To see the output from when your computer started, run dmesg(8). If it has been replaced with other messages, look at /var/run/dmesg.boot.

Want colour in your directory listings? Use ls -G. ls -F is also useful, and they can be combined as “ls -FG”.

Want to find a specific port, just type the following under /usr/ports or one its subdirectories:make search name=<port-name>ormake search key=<keyword>

Want to know how many words, lines, or bytes are contained in a file? Type wc filename.

Want to see how much virtual memory you’re using? Just type “swapinfo” to be shown information about the usage of your swap partitions.

Want to strip UTF-8 BOM(Byte Order Mark) from given files?sed -e '1s/^\xef\xbb\xbf//' < bomfile > newfile

Want to use sed(1) to edit a file in place? Well, to replace every ’e’ with an ‘o’, in a file named ‘foo’, you can do:sed -i.bak s/e/o/g fooAnd you’ll get a backup of the original in a file named ‘foo.bak’, but if you want no backup:sed -i '' s/e/o/g foo

When you’ve made modifications to a file in vi(1) and then find that you can’t write it, type <ESC>!rm -f % then :w! to force the write.This won’t work if you don’t have write permissions to the directory and probably won’t be suitable if you’re editing through a symbolic link.

You can adjust the volume of various parts of the sound system in your computer by typing mixer <type> <volume>. To get a list of what you can adjust, just type mixer.

You can automatically download and install binary packages by doingpkg install <package>This will also automatically install the packages that are dependencies for the package you install (ie, the packages it needs in order to work.)

You can change the video mode on all consoles by adding something likethe following to /etc/rc.conf:allscreens="80x30"You can use vidcontrol -i mode | grep T for a list of supported text modes.

You can disable tcsh’s terminal beep if you set nobeep.

You can install extra packages for FreeBSD by using the ports system.If you have installed it, you can download, compile, and install software byjust typingcd /usr/ports/<category>/<portname>``make install && make cleanas root. The ports infrastructure will download the software, change it so it works on FreeBSD, compile it, install it, register the installation so it will be possible to automatically uninstall it, and clean out the temporary working space it used. You can remove an installed port you decide you do notwant after all by typingcd /usr/ports/<category>/<portname> make deinstallas root.

You can look through a file in a nice text-based interface by typingless filename

You can make a log of your terminal session with script(1).

You can often get answers to your questions about FreeBSD by searching in theFreeBSD mailing list archives at

You can open up a new split-screen window in (n)vi with :N or :E and then use ^w to switch between the two.

You can permanently set environment variables for your shell by putting them in a startup file for the shell. The name of the startup file varies depending on the shell - csh and tcsh uses .login, bash, sh, ksh and zsh use .profile. When using bash, sh, ksh or zsh, don’t forget to export the variable.

You can press Ctrl-D to quickly exit from a shell, or logout from a login shell.

You can press Ctrl-L while in the shell to clear the screen.

You can press up-arrow or down-arrow to walk through a list of previous commands in tcsh.

You can search for documentation on a keyword by typingapropos keyword

You can set autologout = 30 to have tcsh log you off automatically if you leave the shell idle for more than 30 minutes.

You can use aliases to decrease the amount of typing you need to do to get commands you commonly use. Examples of fairly popular aliases include (in Bourne shell style, as in /bin/sh, bash, ksh, and zsh):alias lf="ls -FA"``alias ll="ls -lA"``alias su="su -m"In csh or tcsh, these would bealias lf ls -FA``alias ll ls -lA``alias su su -mTo remove an alias, you can usually use unalias aliasname. To list all aliases, you can usually type just alias.

You can use /etc/make.conf to control the options used to compile software on your system. Example entries are in /usr/share/examples/etc/make.conf.

You can use pkg info to see a list of packages you have installed.

You can use the ‘fetch’ command to retrieve files over ftp, http or https.fetch download the front page of the FreeBSD web site.

You can use whereis to search standard binary, manual page and source directories for the specified programs. This can be particularly handy when you are trying to find where in the ports tree an application is.Try whereis firefox and whereis whereis.

Want to run the same command again?In tcsh you can type !!.

Want to go the directory you were just in?Type cd -

© Arnold Greyling 2023