Understand Linux file permissions and ownership. Learn to read and modify permissions using chmod, change ownership with chown, and apply security best practices.

Learning Objectives

Read and understand permission strings (rwxrwxrwx)

Change file permissions with chmod

Understand ownership and groups

Apply secure permissions for scripts and config files

Step 1

Set up practice files

Create files to practice permission changes.

Commands to Run

cd ~

mkdir perms-practice && cd perms-practice

touch script.sh config.conf data.txt

ls -l

What This Does

ls -l shows detailed file information including permissions. First column shows permissions string. We'll learn to read and modify these.

Expected Outcome

Three empty files created. ls -l shows permission string like -rw-r--r-- for each file, plus owner, group, size, date.

Pro Tips

1
ls -l shows long format with permissions
2
First character: - = file, d = directory, l = link
3
Next 9 characters: permissions (rwxrwxrwx)
4
Then: owner, group, size, date, filename

Common Mistakes to Avoid

⚠️Not understanding what ls -l output means
⚠️Ignoring permissions when they cause 'Permission denied' errors

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104 — Permissions & Ownership