User & Permission Management Flashcards

Which command displays the numeric UID and GID of the current user along with all supplementary group memberships?

Answer: id

The id command shows the current user's UID, primary GID, and all supplementary group IDs.

What does the command 'newgrp developers' accomplish?

Answer: Starts a subshell with developers as the effective primary group

newgrp opens a new shell session where the specified group becomes the user's effective primary group for that session.

Which useradd option specifies a comment (GECOS field) such as the user's full name?

Answer: -c

The -c option sets the GECOS/comment field, typically used for the user's full name or description.

A file has permissions 664. What is the symbolic equivalent for the 'others' portion?

Answer: r--

The last octal digit 4 equals binary 100, which maps to read-only (r--).

Which file defines default settings (like UMASK and home directory skeleton path) used by useradd?

Answer: /etc/default/useradd

/etc/default/useradd stores defaults for the useradd command such as SHELL, HOME, INACTIVE, and EXPIRE.

What effect does setting UMASK to 027 have on newly created files?

Answer: Files get permissions 640

A umask of 027 subtracts from the default 666 for files: 666 - 027 = 640 (rw-r-----).

Which command is used to add an existing user 'alice' to the supplementary group 'sudo' without removing her from other groups?

Answer: usermod -aG sudo alice

usermod -aG appends the specified group to the user's supplementary groups; omitting -a would replace all supplementary groups.