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LINUX

NETWORKING

  • TCP DUMP: tcpdump -nqt -s0 -A -i any port 5060 |grep "computer networking" -A 10 -B 10
  • TCP DUMP with portrange: tcpdump -nqt -s0 -A -i any -an portrange 1-25
  • Ping with MTU size: ping 122.152.145.101 -s 1500

ADVANDCE

  • Find & Replace: find ./hoiio/ -type f -exec sed -i "s/<origin_string>/<new_string>/g" {} +
  • Repeat Command n times: for i in {1..10}; do <command>; done
  • curl with digest auth curl --digest --user minh:secret https://minh.com/
  • trace: last -x
  • investigate: grep -iv ': starting\|kernel: .*: Power Button\|watching system buttons\|Stopped Cleaning Up\|Started Crash recovery kernel' /var/log/messages /var/log/syslog /var/log/apcupsd* \| grep -iw 'recover[a-z]*\|power[a-z]*\|shut[a-z ]*down\|rsyslogd\|ups'
  • 10 bigest file: du -a /var/log | sort -n -r | head -n 10

NTP _ CHRONY

/etc/chrony.conf - server 192.168.0.51 iburst prefer
chronyc tracking
chronyc source
chronyc sources -v

systemctl restart chronyd ; watch chronyc tracking
/sbin/hwclock --systohc

SSH

SSH Client Configuration

  • Remote Access ssh -i ~/.ssh/private.key -p 9022 -oKexAlgorithms=+diffie-hellman-group1-sha1 -c aes256-cbc [email protected]

  • Sample: ~/.ssh/config

Host PREFIX* 172.31.*.*
    Port 11922
    StrictHostKeyChecking no
    IdentitiesOnly yes
    UserKnownHostsFile=/dev/null
    KexAlgorithms +diffie-hellman-group1-sha1
    User minh
    IdentityFile ~/.ssh/minh.general.private
    ProxyJump SSHJUMPPOINT

  • SSH Tunnel

  • ssh -L local-port:target-host-address:target-host-port remote-host-address

  • ssh -L 80 172.16.1.2:8080 [email protected]

REDIS

  • install redis-cli by 1 command wget http://download.redis.io/redis-stable.tar.gz && tar xvzf redis-stable.tar.gz && cd redis-stable && make & cp src/redis-cli /usr/bin/

SCREEN

  • CISCO console connect example sudo screen /dev/ttyUSBO 9600
  • Start a new session with session name screen -S <session_name>
  • List running sessions / screens screen -ls
  • Attach to a running session screen -x
  • Attach to a running session with name screen -r <session_name>
  • Detach a running session screen -d <session_name>
  • Kill session ```screen -X -S <session_name> quit

IPTABLES

FLUSH

iptables -P INPUT ACCEPT
iptables -P FORWARD ACCEPT
iptables -P OUTPUT ACCEPT

iptables -t nat -F
iptables -t mangle -F
iptables -F
iptables -X

nft flush ruleset

RESET COUNTER

iptables -Z -L -v

OPENSSL

  • generate ssl key & cert openssl req -x509 -nodes -days 365 -newkey rsa:2048 -keyout selfsigned.key -out selfsigned.crt
  • print out certificate x509 in text form: openssl x509 -text -noout -in github_com.csr
  • print out certificate signing request in text form: openssl req -text -in x.CSR

OPENVPN3

wget https://swupdate.openvpn.net/repos/openvpn-repo-pkg-key.pub
apt-key add openvpn-repo-pkg-key.pub
wget -O /etc/apt/sources.list.d/openvpn3.list https://swupdate.openvpn.net/community/openvpn3/repos/openvpn3-buster.list
apt update
apt install openvpn3
mkdir /etc/openvpn3/client
openvpn3 session-start --config /etc/openvpn3/client/mind.ovpn
openvpn3 sessions-list
openvpn3 session-manage --disconnect  --config /etc/openvpn3/client/mind.ovpn

MACOS X

  • Dock Hide Time
defaults write com.apple.dock autohide-time-modifier -int 0
killall Dock

defaults delete com.apple.Dock autohide-delay

  • Startup Volume sudo nvram StartupMute=%01

  • Disable Power Button defaults write com.apple.loginwindow PowerButtonSleepsSystem -bool yes

  • Mac Name

sudo scutil --set HostName <new host name>
sudo scutil --set LocalHostName <new host name>
sudo scutil --set ComputerName <new name>
dscacheutil -flushcache

GIT

# track:
git remote add upstream [email protected]:signalwire/freeswitch.git

# Update:
git fetch upstream
git rebase upstream/master
git push
git push --tags

# new branch from tag
git checkout tags/v1.10.11 -b v1.10.11-libre-a