3.2 Log In and Switch Users in Multiuser Targets

RHEL is a multiuser operating system: many users and services can be active at once. The RHCSA objective to log in and switch users in multiuser targets means you must understand systemd targets that define the system’s operating mode, how interactive logins work, and how to change identity with su (and related tools) without losing track of environment, home directory, and privileges.

Multiuser Targets vs Graphical Targets

systemd boots the machine into a target—a synchronization point that pulls in a set of units (services, sockets, mounts).

On many RHEL servers the default target is multiuser.target. Confirm with:

systemctl get-default

Change the persistent default (survives reboot):

sudo systemctl set-default multiuser.target
sudo systemctl set-default graphical.target

Switch the running system without permanently changing the default:

sudo systemctl isolate multiuser.target

Isolating is immediate operational change; set-default is what EX200 cares about when the grader reboots. Remember the exam rule: if the requirement is “after reboot the system comes up multi-user without a GUI,” set-default multiuser.target is the durable fix—not only a temporary isolate.

multiuser.target still allows multiple simultaneous logins: local virtual terminals, serial consoles, and SSH sessions. “Multiuser” does not mean “only one person at a time”; it means the system is fully up for concurrent users and services.

Logging In

Local text logins

On a console, a getty presents a login prompt on a tty (for example tty1). Enter username, then password. A successful login starts a shell according to the account’s settings in /etc/passwd (shell field) and profile files.

Switch virtual consoles with Ctrl+Alt+F1, Ctrl+Alt+F2, and similar combinations on physical or many hypervisor consoles (exact key mapping can depend on the virtualization client). Each tty can host a different logged-in user—classic multiuser behavior.

Remote logins

SSH logins (previous section) also land you in the multiuser environment. From the system’s point of view, an SSH session is another login session associated with a pseudo-terminal (pts), visible in tools like who and w.

Identifying who you are

Always verify identity before changing system files:

whoami          # current effective username
id              # uid, gid, and supplementary groups
id student      # inspect another account without switching

Session inventory:

who             # logged-in users, terminals, login times
w               # who + load and what each session is running
logname         # original login name in some session types

These commands prevent costly mistakes—editing as the wrong user, writing into the wrong home directory, or assuming you still have root when you do not.

Switching Users with su

su (“substitute user” / “switch user”) changes the active user of your shell session. Default with no username is to switch to root (password required unless already root).

su username vs su - username

This distinction is exam-critical:

su student
su - student
su -l student     # same idea as su - student (login shell)

When you need the target user’s full login environment—correct $HOME, path, and profile scripts—use su -. Administrators who only run su without the dash sometimes see missing variables, wrong cwd, or tools not on PATH, then waste time debugging “broken” software that is really an environment problem.

Examples:

su -                  # become root with login shell (root password)
su - bob              # become bob with login shell
su -c 'id' alice      # run one command as alice, then return

Exit the switched shell with exit to return to the previous user.

Password prompts

• Switching to root with su generally requires the root password (unless policy/tools differ).
• Switching to another ordinary user requires that user’s password when you are not already privileged.
• sudo (covered more under security/user admin topics) can allow permitted commands as another user using your password and sudoers policy—different mechanism from su.

For this objective, master su / su - behavior and know when a login shell is required.

Root vs Ordinary Users and Home Directories

The shell expands ~ to the current user’s home. After su - alice, ~ is alice’s home. After su - to root, ~ is /root. Writing “into home” while still in an old directory or wrong user is a frequent source of “file not found” and permission errors.

Check:

echo $HOME
pwd
ls -ld ~

Why Multiuser Targets Matter for Admin Work

In multiuser.target:

• Network services (including sshd when enabled) can run
• Multiple users can log in and switch identities to test permissions
• You can validate that a service runs without relying on a GUI

RHCSA labs often assume text-mode multiuser operation. If a system is stuck in a rescue-like target or failed units prevent multiuser, logins and network services may be incomplete—tie that mental model to later boot-troubleshooting objectives.

Practical Workflows for the Exam

1. Confirm default target: systemctl get-default → set if the task requires multiuser or graphical after reboot.
2. Log in as a specified user (console or SSH).
3. Verify with whoami / id before editing restricted paths.
4. Switch to root or another account with su - when you need a proper login environment.
5. Run the administrative task; exit nested shells cleanly so you know which identity is active.
6. Reboot only when required—and ensure default target and enabled services match the specification so the state persists.

Common Pitfalls

• Using su without - and then wondering why $HOME or PATH is wrong
• Assuming root’s home is under /home
• Changing the running target with isolate but forgetting set-default when persistence is required
• Losing track of nested su sessions (run whoami often)
• Expecting graphical tools when the system is correctly left on multiuser.target

If you can log in locally and remotely, prove identity, switch users with correct login-shell semantics, and set a default multiuser target that survives reboot, you have met this objective’s intent.