Sameer becomes twice as fast

Ctrl+R then type: df
# Shows: df -h
Ctrl+R again:
# Shows: df -h | awk '$5+0>=90'

history | grep "grep.*ERROR"     # see all your error-searching commands
history | grep systemctl         # see all your service commands
!!                               # run the last command again
!grep                            # run the last command that started with grep
!sudo                            # run the last sudo command

nano ~/.bashrc

# Add these:
alias ll='ls -lhrt'
alias la='ls -la'
alias ..='cd ..'
alias ...='cd ../..'
alias grep='grep --color=auto'
alias df='df -h'
alias free='free -h'
alias ports='ss -tlnp'
alias myip='ip addr show eth0 | grep "inet "'
alias logs='tail -f /var/log/syslog'
alias applog='tail -f /opt/app/logs/app.log'
alias errgrep='grep -C 5 "ERROR"'

source ~/.bashrc   # apply changes immediately

# Start a named session:
screen -S incident-deploy

# Detach (go back to normal terminal, process keeps running):
Ctrl+A then D

# List sessions:
screen -ls

# Reattach to a session:
screen -r incident-deploy

# tmux (more powerful, more used today):
tmux new -s deploy              # new session named 'deploy'
Ctrl+B then D                   # detach
tmux ls                         # list sessions
tmux attach -t deploy           # reattach

# tmux splits your terminal into panes:
Ctrl+B then %                   # split vertically (two side-by-side terminals)
Ctrl+B then "                   # split horizontally
Ctrl+B then arrow keys          # move between panes
Ctrl+B then Z                   # zoom in/out of current pane

watch -n 2 'df -h'                          # refresh df every 2 seconds
watch -n 3 'ss -tnp | grep 5432 | wc -l'    # watch connection count
watch -n 5 'ps aux --sort=-%cpu | head -10'  # watch top processes
watch -n 1 'tail -5 /var/log/app.log'        # watch last 5 log lines
watch -d 'free -h'                           # highlight what changed since last refresh

# See output AND save to file at the same time (tee):
./deployment.sh | tee deploy_$(date +%Y%m%d_%H%M%S).log
# You watch the output AND have a log file

# Append to a log:
echo "$(date): restarted nginx" >> /var/log/ops.log

# Redirect errors to a file, keep normal output on screen:
command 2>errors.log

# Both stdout and stderr to file:
command > all_output.log 2>&1

# Find all logs over 1GB and show their sizes:
find /var/log -size +1G -exec ls -lh {} \;

# Find all .conf files modified in last 24 hours:
find /etc -name "*.conf" -mtime -1

# Find and delete old compressed logs older than 30 days:
find /opt/app/logs -name "*.gz" -mtime +30 -delete

# Find all files NOT owned by tomcat in the app directory:
find /opt/app -not -user tomcat -ls

# Top 10 most active IPs in nginx access log:
awk '{print $1}' /var/log/nginx/access.log | sort | uniq -c | sort -rn | head -10

# Count HTTP status codes:
awk '{print $9}' /var/log/nginx/access.log | sort | uniq -c | sort -rn

# Find the 5 largest files by any user on the system:
find / -type f -printf '%s %p\n' 2>/dev/null | sort -rn | head -5

# Count lines matching a pattern per day:
grep "ERROR" app.log | cut -d' ' -f1 | sort | uniq -c

# Add to ~/.bashrc:
cdlog() { cd /opt/"$1"/logs && ls -lrt; }
# Usage: cdlog myapp  — goes to /opt/myapp/logs and lists files

errcheck() { grep -C 5 "ERROR" /opt/"$1"/logs/*.log | tail -50; }
# Usage: errcheck payment  — shows last 50 errors with context

svcrestart() { sudo systemctl restart "$1" && journalctl -u "$1" -f -n 20; }
# Usage: svcrestart nginx  — restart and immediately watch logs