Ubuntu/Commands

Commands | dig | Mail Server CLI | openssl | sed

SCP

scp [(username@)host:filepath] [(username@)destination:file path]

spaces within files/folders can something be resolved by adding quotes around the entire value with \\ or \ followed by a space where the space exists.

i.e. scp "a@10.0.0.1:/home/folder\\ with \\ spaces/test.text" b@10.0.0.2:/home/

scp through ssh proxy

~$ scp -i ~/.ssh/id_ed25519 -o ProxyJump=user@proxyserver ./sourcefile user@destinationserver:/destinationfile

ln (symlink)

create symlink

sudo ln -s source linkname
i.e. sudo ln -s ../sites-available/helpdesk helpdesk

unlink symlink

sudo unlink link.name
i.e. sudo unlink helpdesk

send process to background

• send command to background process, add & at the end of the command
• CRTL+Z pauses a process
• bg sends paused process to background
• jobs shows processes running in the background
• fg brings it back to the foreground

apt-get/apt-cache

apt-cache search keyword

apt-get install keyword

Update

always update the repos before installing or upgrading packages

~$ sudo apt-get update

if you wanted to update all of the packages installed on your machine, you could do this:

~$ sudo apt-get update && sudo apt-get upgrade -y

List all installed pacakges

~$ sudo apt list --installed

Search for package in the repo

~$ apt-cache search keyword

check if package is installed

dpkg -s [package]
i.e. dpkg -s apache-perl

WOL - Wake on Lan

~$sudo apt-get install etherwake
~$sudo wakeonlan MAC-Address-Here
or
~$sudo etherwake MAC-Address-Here
or
~$sudo etherwake -D MAC-Address-Here

add user

adduser [newuser]

add user to sudoer

visudo

~$ visudo
root       ALL=(ALL:ALL) ALL
newuser ALL=(ALL:ALL) ALL

add to sudo group

you may have a sudo group that you can simply add the user to.

add to the sudo group
~$ sudo usermod -a -G [group] [user]
i.e. sudo usermod -a -G sudo Joe

check to verify they are part of the group
~$ getent group sudo
sudo:x:27:Bob,Joe

check listening port

check to see if the service is running and listening on port 22

sudo egrep -i sshd /var/log/*log|more
or
sudo netstat -lp

tcpdump

check for any ssh session that is not originating from your IP

~$ sudo tcpdump -i venet0:0 port 22 and not host [your IP]

chmod

permissions

Permissions	Owner	Group	[Collapse]  Others
777	rwx	rwx	rwx
666	rw-	rw-	rw-
555	r-x	r-x	r-x
444	r--	r--	r--
333	-wx	-wx	-wx
222	-w-	-w-	-w-
111	--x	--x	--x
000	---	---	---

wget

specify the destination file name and location

-O

example: download source.file and save it to destination.file under /home/pi/
~$ wget -O /home/pi/destination.file https://source.server/source.file

Do not check a site's certificate (valuable when downloading from a site with a self-signed cert)

--no-check-certificate

example: using pdsh, tell a bunch of computers to download file from https server and save it without checking the certificate

~$ pdsh -w ssh:pi@rpi-wb[2-24] 'wget -O /opt/vc/src/hello_pi/hello_video/20150730_1854_56.avi https://server.com/images/manual/20150730_1854_56.avi --no-check-certificate'