1. Locating Files with find

# Search every directory for a file called nginx.conf
find / -type f -name nginx.conf

# Limit the search to /etc for faster results
find /etc -type f -name nginx.conf

# Wildcards: list every .conf file under /etc
find /etc -type f -name "*.conf"

# Combine wildcard and prefix
find /etc -type f -name "nginx*"

2. Touching and Backdating Files

# Display full metadata
stat /opt/demo.cfg

# Create or update mtime to a specific date
touch -m -d "2021-08-02 09:00" /opt/report.txt

3. Filtering by Modification Age

# Files modified more than 3 days ago
find /opt -type f -name "*.log" -mtime +3

# Files modified within the last 24 hours
find /opt -type f -mtime -1

4. Deleting Old Logs Safely

# Dry-run first
find /var/log -type f -name "*.log" -mtime +10

# Execute deletion
find /var/log -type f -name "*.log" -mtime +10 -exec rm -f {} \;

5. Generating Dummy Files of Abritrary Size

# 1 MiB file
dd if=/dev/zero of=dummy_1M.img bs=1M count=1

# 100 MiB file
dd if=/dev/zero of=dummy_100M.img bs=1M count=100

# Verify
ls -lh dummy_*

6. Finding by Size

# Exact match
find . -type f -size 5M

# Greater than 5 MiB
find . -type f -size +5M

# Less than 1 MiB
find . -type f -size -1M

# System-wide hunt for giants
find / -xdev -type f -size +100M 2>/dev/null

7. Visualising Directory Trees with tree

# Install once
yum install -y tree

# Show /var/log hierarchy
tree /var/log

8. Cloning a Virtual Machine

1. Power off the source VM.
2. Right-click → Clone → Full clone.
3. Boot the clone and assign a unique hostname/IP.

9. Remote Copy with scp

Download

# Copy single file
scp user@192.168.1.10:/opt/data.csv /opt/

# Recursive directory
scp -r user@192.168.1.10:/opt/project /opt/

Upload

# File
scp /opt/report.txt user@192.168.1.10:/opt/

# Directory
scp -r /opt/folder user@192.168.1.10:/opt/

Ensure sshd is active:

systemctl enable --now sshd

10. Automated Backups via cron

# Discover full path to tar
which tar   # → /usr/bin/tar

# Edit crontab
crontab -e

# Every day at 03:15, create a timestamped archive
15 3 * * * /usr/bin/tar -czf /backup/etc-$(date '+\%Y\%m\%d\%H\%M\%S').tar.gz /etc

# List current jobs
crontab -l

11. Date Formating Quick Reference

date '+%F %T'        # 2024-07-15 14:30:00
date '+%Y%m%d%H%M%S' # 20240715143000