~/cheatsheets/linux
Published on

Linux

Heredoc

The string after << indicates where to stop

cat << EndOfMessage
This is line 1.
This is line 2.
Line 3.
EndOfMessage

To send these lines to a file, use:

cat > $FILE <<- EOM
Line 1.
Line 2.
EOM

SCP/SSH

SCP to Server

SCP all files in /path/to/files/ to 10.10.10.10 to serverDIR

scp -r /path/to/files/* 10.10.10.10:./[serverDIR]

SCP From Server

SCP all files from serverDIR on 10.10.10.10 to the current local directory

scp 10.10.10.10:./[serverDIR]/* .

SSH Tunnels

Create a SSH tunnel that uses port 9925 on the localhost. When traffic is received on localhost:9925 it will route it to 10.10.10.10:25

ssh -L 9925:localhost:25 10.10.10.10

Create a SSH tunnel that uses port 8282 and 9282 on the localhost. When traffic is received on localhost:8282 it will route it to 10.10.10.10:8280 and when traffic is received on localhost:9282 it will route it to 10.10.10.10:9280

ssh -L 8282:localhost:8280 -L 9282:localhost:9280 10.10.10.10

Create SSH tunnel that when a connection is made to the port 5044 on 10.10.10.10 it should be forwarded to port 5044 on your local machine.

ssh -R 5044:localhost:5044 10.10.10.10

Copy contents of a remote file into clipboard, using pbcopy

ssh -i ~/path/to/key ubuntu@[IP] "cat [path-to-file]" | pbcopy

Create a symbolic link called myApplication that is linked to myApplication_1.0.3

ln -s myApplication_1.0.3 myApplication

Exploratory Commands

Find processes running on specific port

sudo lsof -i tcp:port

Find biggest 30 files

sudo find -type f -exec du -Sh {} + | sort -rh | head -n 30

Find open file handles, by pid and name

lsof | awk '{ print $2 " " $1; }' | sort -rn | uniq -c | sort -rn | head -20

NC

nc -z -v {host} {port}

Kill commands

Kill multiple processes

for pid in $(ps -ef | grep "process name" | awk '{print $2}'); do kill -9 $pid; done

pkill -9 {process name}

Remove from Systemd

systemctl stop [servicename]
systemctl disable [servicename]
rm /etc/systemd/system/[servicename]
rm /etc/systemd/system/[servicename] symlinks that might be related
systemctl daemon-reload
systemctl reset-failed

iptables

Redirect port 80 to 9999

iptables -t nat -A PREROUTING -p tcp -m tcp --dport 80 -j REDIRECT --to-ports 9999

Redirect port 443 to 9991

iptables -t nat -A PREROUTING -p tcp -m tcp --dport 443 -j REDIRECT --to-ports 9991