Linux Commands: umask, su, sudo, chown

Which permission group applies only to the owner of a file or directory?

What permission type allows a user to modify a file or directory?

Which command allows you to change a file's group ownership?

What does the 'id' command display?

Which file type refers to a device handling data in blocks, like a hard-drive?

What does the 'umask' command set?

What is the binary equivalent of the file mode 'rw- rw- r--'?

When using the 'chown' command with the argument 'nika:users', what ownership changes occur?

Which command is used to change the group ownership of a file in Linux?

In octal notation, what is the permission mode for a file with 'rw- r-- r--' permissions?

Which permission type allows a user to read and execute a file but not modify it?

What is the binary equivalent of the file mode 'rw- r-- r--'?

Which file type handles data in blocks, like a hard drive?

What does the 'su' command allow you to do in Linux?

What does the 'passwd' command enable users to change in Linux?

What is the binary equivalent of the file mode '*Property of STI: rw- rw- rw-'?

umask Command

The umask command sets default permissions for newly created files and directories.
A common binary umask is 0002, which results in file permissions of rw-rw-r--.

Permissions and Modes

Original file modes can be expressed in octal notation:
- 777: Full permissions for everyone (not recommended).
- 755: Owner can read, write, execute; others can read and execute.
- 700: Owner has all permissions; others have none (private use).
- 666: All users can read/write.
- 644: Owner can read/write; others can only read.
- 600: Owner can read/write; others have no permissions.

chown Command

The chown command changes file ownership.
Sample usage:
- nika: Changes ownership to user "nika".
- nika:users: Changes ownership to user “nika” and group “users”.
- :admins: Changes group ownership to “admins”.

File Permission Values

Octal to binary notations:
- 0 - 000 (no permissions)
- 1 - 001 (execute)
- 2 - 010 (write)
- 3 - 011 (write + execute)
- 4 - 100 (read)
- 5 - 101 (read + execute)
- 6 - 110 (read + write)
- 7 - 111 (read + write + execute)

Directory Permission Values

Directory permissions are critical for managing access:
- 777: Full permissions (not recommended).
- 755: Owner has full access; others can list.
- 700: Directory is private to the owner.

Symbolic Notation for Permissions

Represents permissions using combinations of symbols:
- u: User (owner)
- g: Group owner
- o: Others
- a: All (user, group, others)
Symbolic commands examples:
- u+x: Grants execute permission to the owner.
- u-x: Revokes execute permission from the owner.
- go=rw: Sets group and others to read/write permissions, removes execute.
- u+x, go=rx: Grants execute to owner; group and others get read/execute permissions.

Overall Best Practices

Avoid using 777 permissions to maintain security.
Use umask carefully to default to safer permissions.
Regularly review file and directory permissions to ensure they meet security needs.

Test your knowledge on Linux commands such as umask, su, sudo, and chown. Understand how to set permissions and change ownership of files in a Linux environment.