Essential Linux Commands: Files, Directories, Viewing, and Searching

The first time you SSH into your server, all you get is a blank terminal. Don't let it intimidate you. Get comfortable with the dozen or so commands below and you'll cover most day-to-day server work. Examples assume Ubuntu/Debian.

Getting Around

Start with "where am I, what's here, how do I get elsewhere?"

pwd             # print the full path of the current directory
ls              # list what's in the current directory
ls -lh          # long format with human-readable file sizes
ls -a           # include hidden files (those starting with .)
cd /var/www     # change into a directory (absolute path)
cd ..           # go up one level
cd              # jump straight to your home directory

Tip: press Tab while typing a path to auto-complete it. Less typing, fewer typos.

Working with Files and Directories

Creating, copying, moving, and deleting are your bread and butter.

mkdir logs           # create a directory
mkdir -p a/b/c       # create nested directories in one go
touch app.log        # create an empty file
cp src.txt dst.txt   # copy a file
cp -r dir1 dir2      # copy a directory recursively
mv old.txt new.txt   # rename or move a file
rm file.txt          # delete a file
rm -r olddir         # delete a directory recursively

There is no recycle bin for rm — once it's gone, it's gone. Double-check the path with ls before deleting, and treat rm -rf with respect, especially near / or your home directory.

Reading File Contents

You don't always need an editor. These are quicker for a glance.

cat config.yaml       # dump the whole file to the screen
less big.log          # page through a file; arrow keys scroll, q quits
head -n 20 app.log    # show the first 20 lines
tail -n 50 app.log    # show the last 50 lines
tail -f app.log       # follow new log lines as they're written

Reach for less on large files — cat floods your screen all at once. tail -f is a favorite for watching logs roll in while you troubleshoot.

Searching and Finding

Use grep to search inside files, and find to locate files by name or attributes.

grep "error" app.log            # find lines containing "error"
grep -i "error" app.log         # case-insensitive match
grep -rn "timeout" /etc/nginx   # search a directory, show line numbers
find . -name "*.conf"           # find files by name under the current dir
find /var/log -mtime -1         # files modified within the last day

Pipes and Redirection

Chaining commands is where the shell really earns its keep.

ps aux | grep nginx     # feed one command's output into the next
ls -l | less            # page long output instead of scrolling past it
echo "hello" > a.txt    # write to a file, overwriting its contents
echo "world" >> a.txt   # append to the end of a file

| passes output from the left command to the right; > overwrites while >> appends — two ways to save results.

Summary

Find your footing with pwd/ls/cd, manage files with mkdir/cp/mv/rm, read them with cat/less/tail, and track things down with grep/find. Then glue it all together with | and >. When memory fails, command --help or man command is always a keystroke away. A little practice and the terminal quickly becomes second nature.