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Useful Snippets - DevOps

SSH Proxy for Servers​

  • ssh-keygen -b 4096 -N '' # Generate a new key
Host bastion
HostName <bastion_ip>
Port 3222
User root
IdentityFile ~/.ssh/id_rsa
ProxyCommand ssh final_server -W %h:%p
Host final_server
HostName <final_server_ip>
User root
IdentityFile ~/.ssh/id_rsa

nginx proxy​

server {
listen 80;
access_log /srv/logs/app-access.log;
error_log /srv/logs/app-error.log;
location / {
# In case you want to protect the your application very simple with a custom header.
# Without this header nginx won't do nothing.
if ($http_Protect != "jPIuGbawvne19opcxiq") {
return 200 "nothing here";
# It's better to define a variable, otherwise nginx will not work in case that specific host is down - in this case is, but can be a different one.
set $admin;
proxy_pass http://$admin:8000;
proxy_set_header Host $host;
proxy_set_header X-Forwarded-For $remote_addr;
server {
listen 8080;
server_name grafana-{{ cluster_name }}.{{ dns_domain }};
access_log /tmp/grafana-access.log;
error_log /tmp/grafana-error.log;
location / {
set $fwhost grafana;
proxy_pass http://$fwhost:3000;
proxy_set_header Host $host;
proxy_set_header X-Forwarded-For $remote_addr;

Visualize Logs with logstalgia​

brew install logstalgia
# Pipe your logs from the server in logstalgia with --sync
ssh s01 "tail -f /X/X/logs/*/*-access.log | grep -v '==>' | grep -v '^$'" | logstalgia --sync
# s01 is your hostname defined in ~/.ssh/config

Download YouTube Playlist​

  • You can put your playlist as Unlisted to not make it public.
sudo apt-get install youtube-dl ffmpeg libavcodec-extra-53
# Save all music from a playlist as mp4 and mp3 with High Quality
youtube-dl --audio-format mp3 --recode-video mp4 --prefer-free-formats -o "%(title)s(%(id)s).%(ext)s"

Cheat Sheet​

# Decompress a gif image to frames. imagemagick is required.
convert -coalesce "${1}" "${1}".frames/frame.png
# Create a movie for git history and save it as mp4.
gource -s 0.5 -a 1 ./ -1080x720 -o - | ffmpeg -y -r 30 -f image2pipe -vcodec ppm -i - -vcodec libx264 -preset ultrafast -pix_fmt yuv420p -crf 1 -threads 0 -bf 0 gource.mp4
# See DNS requests with tcpdump
tcpdump -i en0 -l -n -e port 53 | awk '{if ($14 == "A?") print $15}'
# Find modified files in last 7 days: `find . -mtime -7 -print`
# Create file with fixed size: `fallocate -l 1G test.rar`
# Test Disk Speed: `hdparm -Tt /dev/sda`
# Local Wireshark with traffic from server
ssh HOST 'sudo tcpdump -U -s0 -w - "not port 22"' | wireshark -k -i -
# Create simple wrapper to view execution of script
strace -e trace=execve -vfo /tmp/strace_execute.log -s 4096 vzctlb $@
# IRC Server: `apt-get install ircd-irc2 irssi`
# 1 - Delete default route: `route del default gw eth0`
# 2 - Add new default route: `route add default gw eth1`

# Speed Python: `python -m cProfile -o report -s calls`
# Check report
import pstats
p = pstats.Stats('report')

# SOCKS Proxy: ssh -D localport host
# PortForwarding: ssh -f -N -L 9906: user@host
# -f puts ssh in background | -N not execute a remote command

# This command will show you the list of IP’s which have logged in is maximum number of connections to your server.
netstat -anp |grep 'tcp\|udp' | awk '{print $5}' | cut -d: -f1 | sort | uniq -c | sort -n
# Clone disk over network
sudo nc -l -p 80 | dd of=/dev/sda bs=16M # First PC (Source)
sudo dd if=/dev/sda | nc IP_SOURCE 80 # Another PC (Destination)
# grant db: `grant all privileges on x.* to user@localhost identified by 'pass';flush privileges;`
# Wine: sudo apt install wine mono-devel mono-complete winetricks && msiexec -i file.exe

alias clipboard="pbcopy" # Mac OS X. Linux: xclip -i -selection clipboard

# Add exif information for SEO image
exiftool -Comment='x' -Keywords='x' -Copyright='x' imagine.jpg

# Create/Update htpasswd
htpasswd -c FILE USER
htpasswd FILE USER
# Mount a folder in OSX
brew install sshfs
sudo sshfs server:/mnt /Volumes/server
# Reboot: echo 1 > /proc/sys/kernel/sysrq | echo b > /proc/sysrq-trigger
# Shutdown: echo o > /proc/sysrq-trigger
# Simple mail alert
HEADERS="From:\r\nTo: ${EMAIL}\r\nSubject: Security Alert!\r\n\r\n"
test $(ps aux | grep trojan | wc -l) -gt 1 && $(echo -e "${HEADERS}" "Security Alert!" | sendmail "${EMAIL}")


Migrate a WordPress website from CLI to cPanel with FTP​

# Install WordPress on the new server and create a new FTP account
# Install ncftpput on the old server
yum install ncftpput
# Copy wp-content to root directory for that specific ftp user account.
ncftpput -R -v -u "" <NEW_Server_IP> / wp-content
# Backup and upload the database from old server to the new one

Show Custom Files for a WordPress Directory​

ls */www | grep -v ".git\|.gitignore\|wp-includes\|wp-admin\|index.php\|wp-activate.php\|wp-blog-header.php\|wp-comments-post.php\|wp-cron.php\|wp-links-opml.php\|wp-load.php\|wp-login.php\|wp-mail.php\|wp-settings.php\|wp-signup.php\|wp-trackback.php\|xmlrpc.php\|license.txt\|readme.html\|wp-config.php\|wp-config-sample.php\|wp-content"

Create new user in WordPress with PHP​

  • Add the next code in the current theme in functions.php file.
  • Refresh the website to execute the code and you can use your new user after that.
add_action('init', 'add_my_user');
function add_my_user() {
$user_id = wp_create_user('admin_new, 'Password12345, 'root@localhost);
$user = get_user_by('id', $user_id);