Files and Directories — Linux Basics | CertQnA

Working with files is the core of Linux administration. Whether you're deploying configs, managing logs, or setting up a server, these commands are your daily toolkit.

Creating Files and Directories

mkdir logs                  # create a directory
mkdir -p app/config/nginx   # create nested directories
touch README.md             # create empty file (or update timestamp)
echo "Hello" > notes.txt   # create file with content

Copying and Moving

cp file.txt backup.txt          # copy file
cp -r src/ dst/                 # copy directory recursively
mv old-name.txt new-name.txt    # rename file
mv file.txt /tmp/               # move to different directory
mv dir/ /opt/app/               # move entire directory

Deleting Files and Directories

rm file.txt            # delete a file
rm -i file.txt         # prompt before deleting
rm -r old-project/     # delete directory recursively
rm -rf /tmp/build/     # force-delete without prompts

Warning: rm -rf permanently deletes files — there is no Recycle Bin or undo. Always double-check the path before running it, especially as root.

Viewing Directory Contents

ls                    # basic listing
ls -l                 # long format with permissions, size, date
ls -la                # include hidden files (starting with .)
ls -lh                # human-readable sizes (KB, MB)
ls -lt                # sort by modification time (newest first)
tree /etc/nginx       # visual tree view (install with apt install tree)

Working with File Content

cat nginx.conf             # print entire file
less nginx.conf            # page through file
head -5 access.log         # first 5 lines
tail -10 error.log         # last 10 lines
tail -f /var/log/syslog    # follow file as it grows
wc -l server.log           # count lines in file

Finding Files

find — powerful, flexible, real-time search

find / -name "nginx.conf"            # find by name
find /var/log -name "*.log"          # wildcard match
find /home -user alice               # files owned by alice
find /tmp -mtime -1                  # modified in last 24 hours
find /opt -size +100M                # files larger than 100 MB
find . -type d                       # find only directories
find . -type f -name "*.sh" -exec chmod +x {} ;

locate — fast indexed search

locate nginx.conf    # instant search (uses a pre-built database)
sudo updatedb        # update the database

Wildcards

ls *.log         # all files ending in .log
ls access*       # all files starting with "access"
ls report?.txt   # report1.txt, report2.txt (? matches single char)
rm temp[0-9].txt # delete temp0.txt through temp9.txt

Symbolic Links

A symbolic link (symlink) is a pointer to another file or directory — like a shortcut on Windows:

ln -s /opt/nginx/conf/nginx.conf /etc/nginx/nginx.conf
# /etc/nginx/nginx.conf now points to /opt/nginx/conf/nginx.conf

ls -l /etc/nginx/nginx.conf
# lrwxrwxrwx 1 root root 30 ... /etc/nginx/nginx.conf -> /opt/nginx/conf/nginx.conf

Symlinks are used extensively in Linux to make versioned software accessible at a stable path (e.g., /usr/bin/python3 → /usr/bin/python3.12).

Archiving and Compressing

tar -czf archive.tar.gz /etc/nginx     # create gzipped archive
tar -xzf archive.tar.gz               # extract
tar -tzf archive.tar.gz               # list contents
zip -r site.zip ./public/             # create zip
unzip site.zip

Next, you'll learn about file permissions — the system that controls who can read, write, and execute each file.