🛠️ Daily Linux Administration Guide

1. User and Group Management

sudo adduser john
sudo usermod -aG sudo john
sudo deluser john --remove-home
sudo groupadd developers
sudo usermod -aG developers john

2. Filesystem & Storage Monitoring

df -hT
du -sh /var/log/*
mount /dev/sdb1 /mnt/mydrive
lsblk
find / -type f -exec du -h {{}} + | sort -rh | head -n 20

3. System Performance & Resource Usage

uptime
free -h
top
ps -eo pid,ppid,cmd,%mem,%cpu --sort=-%cpu | head
iostat -xz 1

4. Security & Updates

sudo apt update && sudo apt upgrade
sudo dnf update
lastlog
who
grep "sshd" /var/log/auth.log | grep "Failed"
sudo fail2ban-client status

5. Package Management

# Debian/Ubuntu
apt install nginx
apt remove apache2

# RedHat/CentOS
dnf install nginx
dnf remove httpd

# List packages
dpkg -l       # Debian
rpm -qa       # RedHat

6. System Services & Processes

systemctl status nginx
systemctl start nginx
systemctl enable nginx
systemctl restart ssh
systemctl list-units --type=service

7. Network Monitoring & Configuration

ip a
sudo ss -tuln
ping google.com
dig jeffmdoyle.com
ip route

8. Firewall (UFW / Firewalld)

# UFW
sudo ufw enable
sudo ufw allow 22/tcp
sudo ufw status verbose

# Firewalld
sudo firewall-cmd --add-port=22/tcp --permanent
sudo firewall-cmd --reload

9. System Logging & Audit

journalctl -xe
sudo tail -f /var/log/syslog
journalctl -u nginx

10. Backups & Scheduled Jobs

crontab -e
crontab -l

# Example: daily at 2am
0 2 * * * /usr/local/bin/backup.sh

rsync -avz /etc /backup/etc/

11. Diagnostic & Troubleshooting Tools

traceroute google.com
netstat -tulpen
inotifywait -m /etc
dmesg | less

12. Useful Admin Utilities

13. Filesystem & Permissions

ls -l /path/to/file
sudo chown user:group file
sudo chmod 755 script.sh

14. Cleanup & Maintenance

sudo apt autoremove
sudo apt clean
find /var/log -type f -size +50M