Hello World

Concepts

Every lab in this repo works the same way: a container is the practice machine, the tasks say what the end state should be, and ./lab check inspects the container to see whether I got there. This lab is the smallest possible example: one file, exact content, exact permissions.

• File content can be written from the shell with redirection (> overwrites, >> appends).
• Unix permissions are three groups (owner, group, others) of read/write/execute bits, often written in octal: 644 means owner rw-, group r--, others r--.

Tasks

Start the lab with ./lab up hello-world, open a shell with ./lab shell hello-world.

1. Write the single line Hello, World! to /root/hello.txt.
2. Set its permissions to 644.

Check your work from the host: ./lab check hello-world

Hints

• echo writes a line; redirect it into the file.
• chmod changes permissions; octal mode works.
• stat -c %a <file> shows the octal mode, cat -A <file> shows hidden characters.

My notes

1. Create and Write Files

touch hello.txt
echo "Hello, World!" > hello.txt

2. Check File Permissions

ls -l hello.txt
stat -c "%a %n" hello.txt

3. Change File Permissions

chmod 644 hello.txt

Remember: - ls -l → Check permissions. - chmod → Change permissions. - > → Overwrite. - >> → Append.

Related

• man chmod, man stat