Useful linux commands

Memory and process info

• show process memory consumption, ordered by memory usage: ps -eO pcpu,pmem,vsz,rsz --sort -rsz,-vsz
• show process info for pid: prtstat pid
• send SIGKILL to all zombie processes: ps -eo pid,state|awk '$2=="Z" {print $1}' | xargs -L1 kill -9

Networking

• show all processes with active ports: lsof -Pnl -i
• dump and protocol decode ip communications: tcpdump -s 1500 -A -vvv
• show listening ports with owning process - IPv4: netstat -Pnl --inet IPv6: netstat -Pnl --inet6
• show routing cache: ip route show cache
• flush routing cache: ip route flush cache
• show nfs exports on remotehost: showmount -e remotehost
• check port on remote host: netcat -zv remotehost port

SSH

• be a socks proxy on localhost port 8080: ssh -D 8080 remotehost
• connect without a pty, without running command and goto background ssh -NTf remotehost

SSH vpn tunnel

ssh -w 0:0 -NTf machineb
ip address add 192.168.99.2 peer 192.168.99.1 dev tun0
ip link set up dev tun0

ip address add 192.168.99.1 peer 192.168.99.2 dev tun0
ip link set up dev tun0

File management

• Show path traversal leading to file namei filename
• Same with mountpoints and mode namei -mx filename