Ubuntu Commands

Packages

apt-get update	get new list of packages
apt-get upgrade	upgrade installed packages
apt-get dist-upgrade	intelligent package upgrade
apt-get install <package>	install package
apt list –installed	list installed packages
<package> –version apt-cache policy <package> dpkg –status <package>	get version/install details
which <package> whereis <package> locate <package> dpkg –listfiles <package>	package file locations

Storage

fdisk -l parted -l lsblk -l lsblk -m lsblk -f	list drives
df	used space in KBs
df -h	used space in MBs, GBs
du	size on disk

Networking

/etc/netplan	interfaces, dhcp & more
netplan apply	apply changes
ip link show	show interfaces, mac address
ethtool <interface>	view interface details
ifconfig ip address	show ip address
nmcli device show <interface>	similar to ipconfig output
dhlcient -r <interface> dhclient <interface>	dhcp release/renew
ip route list route -n	routing table
ping -c 4 bbc.co.uk	number of pings to send
ping -w 25 bbc.co.uk	stop pings after 25 seconds
ping -c 1000 -q bbc.co.uk	quiet output
ping -I <source-ip> bbc.co.uk	set source ip
ping -s 1438 -i 0.2 bbc.co.uk	set packet size and interval
dig TXT +short o-o.myaddr.1.google.com @ns1.google.com	view public ip
dig 7zeros.com dig 7zeros.com MX +short	dns lookup
ip link set <interface> down ip link set dev <int> address <new-mac-address> ip link set <interface> up	steps to change mac address
ip link set <int> mtu <size>	set mtu size
apt-get install vlan	install vlan package
ip link add link <int> name <int.vlan> type vlan id <vlan-id> ip link set <int.vlan> up	set vlan
ip route del default ip route add default via <def-gw>	change default route
ip route add default via <def-gw> dev <int>	change default route & specify interface
w who last netstat	view ssh sessions
ps -t <tty> kill -HUP <bash-pid>	kill ssh session
snmpwalk -v 2c <host>	snmp walk for v2
snmpwalk -v 2c -c <community> <host>	snmp walk with community string
snmpwalk -v 3 -l <security> -u <username> <host>	snmp walk for v3
speedtest-cli –simple speedtest-cli –secure	http test https test
ssh-keygen -R <ip/hostname>	delete ssh keys
sha256sum <filename.xyz>	hash verify checksum
ss	view endpoint sockets

Port Security

nmap -Pn <host>	skip host discovery
nmap -sP 192.168.1.0/24	scan network
nmap -sU <host>	udp scan
nmap -sU -p <port> <host>	specify port
telnet <host> <port>	test port with telnet
nc -z <host> <port>	test port with netcat
nc -v -u -z -w 3 <host> 1190-1194	test udp port
traceroute -T -p <port> <ip>	traceroute on port number
lsof -i -P -n nestat -lntu ss -4altunp	show localhost sockets, listening ports

File Management

cd /path/to	change directory
cd ..	move up one directory
cd –	toggle between current and previous directory
pwd	print working directory
ls -l /path/to	list users & permissions
ls -R /path/to	list nested items
ls -a /path/to	list hidden files
tree -d /path/to/ tree -L <level> /path/to tree -a	list directories in tree list how many levels deep list hidden files
cat <file> less <file> more <file>	view file
mkdir <directory-name>	create directory
touch <filename>	create file
mv <filename> /path/to mv <file> <new-filename> mv <file>{01..99}.txt /path/to	move file rename file move range of files
cp	copy
rm <filename> rm -d <directory> rm -r <directory> rm -i <file/directory> rm -rf <directory>	remove file remove directory recursive prompt before removal remove contents only
find / -type f -name <string>	find files
find . -type d -name <string>	find directories in working directory
find <path> -type f | wc -l	count all items recursively
ln -s /source /symbolic/link	create soft symbolic link
apropos zip	list installed compression applications

Users & Permissions

cat /etc/passwd getent passwd	list users
cat /etc/group getent group	list groups
useradd <username>	create user
usermod -aG sudo <user>	add user to sudo
passwd <username>	change user password
su <username>	change user
addgroup <group-name>	create new group
usermod -a -G <group> <user>	add user to user group
deluser <user> <group>	delete user from group
mkhomedir_helper <user>	create user home directory
chown -R <user>:<group> /path	local user permissions
chmod ugo+rwx /path/to chmod 777 /path/to	change folder permissions (u=user, g=group, o=others) r (read): 4, w (write): 2, x (execute): 1
sudo !!	run previous command with sudo
curl https://download/url wget https://download/url	download from url
wget https://download <short-filename.xyz>	shortened download filename

Firewall

ufw status	show ufw firewall status
ufw allow 53 ufw allow 25/tcp ufw reject telnet	allow/block ports through firewall
ufw allow in http ufw reject out smtp	in and out rules
ipset list	list iptables address lists
iptables -S iptables -L	list iptables firewall rules
iptables -t nat -L iptables -t nat -L -n -v	list nat rules

Packet Capture

tcpdump -D	list capture interfaces
tcpdump -i <interface>	capture on interface
tcpdump -w <filename.pcap>	capture to file
tcpdump -r <filename.pcap>	read captured packets
tcpdump port 22	filter capture on port
tcpdump tcp	filter capture on tcp only
tcpdump net <subnet>	capture on subnet range
tcpdump host <src> and <dst>	capture 2-way traffic

Logs

dmesg	display kernel buffer
/var/log	log files location

Vim

vim <filename>	create/edit file
i	INSERT to make changes
ESC key	exit out of INSERT mode
:q!	quit without making changes
:wq	write and quit
gg	go to beginning of file
shift + g	go to end of file
:<line-number>	go to line number
/<string>	search for string
:s/<pattern>/<replacement>/	find and replace next occurrence
:%s/<pattern>/<replacement>/g	find and replace all occurrences
dG	delete all text

OpenSSL

openssl pkcs12 -export -out cert.p12 -in <cert>.pem -inkey <privkey>.pem

export cert and key