Unix Commands

Unix Commands

This post is part of a project to move my old reference material to my blog. Before 2012, when I accessed the same pieces of code or general information multiple times, I would write a quick HTML page for my own reference and put it on a personal site. Later, I published these pages online. Some of the pages still get used and now I want to make them available on my blog.

Photo by [Torkild Retvedt](https://cdn.hashnode.com/res/hashnode/image/upload/v1627410418528/oxrdioGq4.html) under [CC BY-SA 2.0](https://creativecommons.org/licenses/by-sa/2.0/)Photo by Torkild Retvedt under CC BY-SA 2.0

This is a short list of frequently-used commands for OpenBSD. Many of them are common with most Unix-like platforms. The text is broken into sections designated by the titles in larger print. For each command, the text to type at the prompt will appear first, in monospace font. A short blurb describing the command then follows.

Logging Out and Shutting Down


Log current user out. Displays login: prompt for another user


Shut down the operating system. Same as typing shutdown -h now


Reboot the operating system. Same as typing shutdown -r now

Directory Management


Output what directory you’re currently in

cd x

Change directory to x

pushd x

Same as cd, but saves the directory you were in when you executed the command. Type popd to return to the saved directory

mkdir x

Make a new directory called x

rmdir x

Remove directory x

rm -r x

Remove directory x and all files and directories within


List files and directories in current directory. Use -l to get details, -a to get hidden files, -F to id executables, files, and directories

find / -name x

Search all directories for x

mkdir /mnt/sharename
sudo mount -f cifs //servername/sharename -o username=username,password=password /mnt/sharename

Mounts a Windows share called sharename on the server called servername. Replace username and password with appropriate credentials.

File Management

rm x

Remove file x

rm -r x

Remove directory x and all files and directories within

cp x.txt y.txt

Copy x.txt and name the copy y.txt

mv x.txt y.txt

Move (rename) x.txt to y.txt

df -h

Display disk usage. The -h switch makes numbers human-friendly

Disk Management

mount /wd0a files

Adds the disk wd0 (IDE primary master. wd1 would be IDE primary slave, etc) partition a to directory files. files must exist

umount files

Unmount the device mounted to the directory files



Unix manual. Type man x for a manual on a specific command

x | more

Filter that will pause and wait for user input when the command teakes up more than one screen


Elevate access to root privileges

ps -aux

See resources each process is using. Use | head -5 to just get the top 5 lines of the command

mail -s “x” y

Send email to y (email address) with subject x. Type your message and press Ctrl+D

alias x=’y’

Set an alias so when you type x, the command y executes

Text Viewing and Editing

cat x

Displays contents of file x on screen


Opens full-screen and provides file editing utilities. Exit by hitting Esc, type :wq to save and exit or :q! to exit without saving. Learn more about vi at http://staff.washington.edu/rells/R110/

User Management


Create new user. Accept defaults for most prompts. Enter username and password when prompted. If you want user to have access to su, type wheel when prompted for what groups to invite user to

echo ‘x ALL=(ALL) ALL’ >> /etc/sudoers

Add existing user x to the sudoers list, giving them access to sudo command


Remove an existing user

cat /etc/passwd | cut -d: -f1 | grep -v \#

List existing users


See who you’re logged in as


See what users are currently logged in and what they’re doing

chsh -s /bin/ksh x

Change the default shell to ksh for user x


tar cvzf x.tgz y

Combine all files in directory y and write them to a file called x.tgz. Will be written back as a directory when extracted

tar tzf x.tgz

Display the contents of x.tgz

tar xvzf x.tgz

Extract contents of x.tgz in current directory

Apache Control

apachectl start

Start Apache web server

apachectl stop

Stop Apache

Adding Software

export PKG_PATH=ftp://ftp.openbsd.org/pub/OpenBSD/4.7/packages/amd64

Sets the package path. This is the location new packages will be downloaded from

pkg_add -r -v x

Install package x


ssh x@y

Connect to an SSH server as x at location y


Generate private and public keys to use with public key authentication. You may leave default filename but enter a long passphrase (16+ characters).

After running, append ~/.ssh/id_rsa.pub to server’s ~/.ssh/authorized_keys file using the command below.

cat x >> ~/.ssh/authorized_keys

Allow client with public key x to connect using public key authentication. x can be found in client’s ~/.ssh/id_rsa.pub file after running command above.

kill -HUP `cat /var/run/sshd.pid`

Restart SSH daemon after changing config file

kill x

Boot a remote user off SSH. x is the PID for their sshd process. The PID can be found by running ps -aux and finding the COMMAND labeled sshd: username

http://www.computerglitch.net/blog/attic/adding-a-new-hard-drive-to-openbsd.html Adding a new hard drive disk

Reboot the operating system. Same as typing shutdown -r now