Navigating the Linux Filesystem

Navigating the Linux Filesystem

New Linux administrators often feel lost because they cannot see the filesystem visually. The solution is not a GUI file manager — it is four commands: pwd, ls, cd, and find. Master these and you can navigate any Linux server confidently, even a system you have never seen before.

Absolute vs relative paths

Every file on Ubuntu has two types of addresses: absolute and relative.

Special path shortcuts:

# Show your current location in the filesystem
pwd

Output

/home/irfan

The cd command

# Go to an absolute path
cd /var/log

# Go to a relative path (from current directory)
cd nginx          # Goes to /var/log/nginx if you were in /var/log

# Go to your home directory (all three are identical)
cd
cd ~
cd $HOME

# Go back to the previous directory
cd -

# Go up one level
cd ..

# Go up two levels
cd ../..

# Go to a path with spaces in the name (use quotes)
cd "/var/lib/mysql data"

💡 TIP: cd - is one of the most useful navigation shortcuts. It works exactly like the Back button in a browser — one press returns you to where you were before your last cd. Use it when jumping between two directories repeatedly.

The ls command

ls is the command you will run hundreds of times per day. The flags that matter most:

# Basic listing
ls /etc

# Long format: permissions, owner, size, date, name
ls -l /etc

# Long format including hidden files (starting with .)
ls -la /home/irfan

# Human-readable file sizes (K, M, G instead of bytes)
ls -lh /var/log

# Sort by modification time, newest first
ls -lt /var/log

# Reverse sort (oldest first)
ls -ltr /var/log

# Recursive: list all files in directory and subdirectories
ls -R /etc/nginx/

Understanding the ls -la output

drwxr-xr-x  2 root root 4096 Jun 10 09:00 nginx
-rw-r--r--  1 root root 1823 Jun 10 09:00 nginx.conf
lrwxrwxrwx  1 root root   34 Jun 10 09:00 sites-enabled -> ../sites-available/default
↑            ↑    ↑    ↑    ↑              ↑
type+perms  links owner group size   date   name

File types:
d = directory
- = regular file
l = symbolic link
c = character device
b = block device

Finding files with find

find is the most powerful file search tool on Linux. It searches the filesystem in real time (no index) and supports filtering by name, type, size, owner, permissions, and modification time.

# Find files by name
find /etc -name "nginx.conf"

# Find files by name pattern (case-insensitive)
find /var/log -iname "*.log"

# Find only files (not directories)
find /home -type f -name "*.sh"

# Find only directories
find /var -type d -name "cache"

# Find files modified in the last 24 hours
find /var/log -mtime -1

# Find files larger than 100 MB
find /var -size +100M

# Find files owned by a specific user
find /home -user irfan

# Find files with specific permissions
find /etc -perm 777

Combining find with actions:

# Print the size of each .log file over 10 MB
find /var/log -name "*.log" -size +10M -exec du -sh {} \;

# Delete files older than 30 days in /tmp
find /tmp -type f -mtime +30 -delete

# Show the 10 largest files in /var
find /var -type f -printf "%s	%p
" | sort -rn | head -10

Finding files with locate

locate uses a pre-built index for fast searches. It is much faster than find for simple name searches but only searches files that existed when the index was last updated.

# Install if not present
sudo apt install mlocate

# Update the index (run this after installing new software)
sudo updatedb

# Find a file by name
locate nginx.conf

# Case-insensitive search
locate -i php.ini

# Show only files that actually exist (exclude deleted files in the index)
locate -e nginx.conf

📝 NOTE: locate can return results for files that no longer exist if the database has not been updated. Always use locate -e to filter out stale results, or run sudo updatedb first.

Finding commands with which and whereis

# Find where a command binary is installed
which nginx
which python3

Output

/usr/sbin/nginx
/usr/bin/python3

# Find binary, man page, and source locations
whereis nginx

Output

nginx: /usr/sbin/nginx /usr/lib/nginx /etc/nginx /usr/share/doc/nginx

# Find which package owns a binary
dpkg -S $(which nginx)

Output

nginx-core: /usr/sbin/nginx

Disk usage navigation

When disk space is low, these commands help you find what is using it:

# Show disk space on all mounted filesystems
df -h

# Show total disk usage of a directory
du -sh /var/log

# Show disk usage of each item in a directory, sorted
du -sh /var/log/* | sort -h

# Find the top 10 largest directories under /var
du -h /var --max-depth=2 2>/dev/null | sort -rh | head -10

# Show inode usage (important when many small files exist)
df -i

Example: finding what is filling /var

$ du -sh /var/* 2>/dev/null | sort -rh | head -5
8.2G  /var/lib
2.1G  /var/log
450M  /var/cache
120M  /var/backups
 48M  /var/snap

Conclusion

Navigating the Linux filesystem is a four-command skill: pwd tells you where you are, ls shows what is there, cd moves you around, and find locates any file anywhere. Once these are instinctive, navigating an unfamiliar Ubuntu server feels natural rather than frustrating.