EX200 Manage security — Timed 15 Questions

Question 1

A junior admin needs to ensure that the 'apache' user (UID 48) cannot log in via SSH or console. Which command achieves this?

Accepted Answer

usermod -s /sbin/nologin apache. Option A is correct because setting the user's login shell to `/sbin/nologin` prevents the user from obtaining an interactive shell via SSH or console login. When the user attempts to log in, the system executes `/sbin/nologin`, which prints a polite message and exits immediately, effectively denying shell access while leaving other services (e.g., Apache) functional.

Answer

passwd -l apache

Answer

chage -l apache

Answer

usermod -e 1 apache

Question 2

An administrator runs 'getenforce' and sees 'Enforcing'. They then run 'setenforce 0' but SELinux still denies access to a custom application. What is the most likely reason?

Accepted Answer

The issue is due to file permissions or ACLs, not SELinux.. Option C is correct because `setenforce 0` switches SELinux to permissive mode, which logs but does not enforce denials. If access is still denied after this command, the issue is not caused by SELinux enforcement but by traditional Linux file permissions (DAC) or ACLs. The administrator should check `ls -l` and `getfacl` to verify the file's ownership and permissions.

Answer

SELinux is in enforcing mode and the policy is misconfigured.

Answer

The application's SELinux context is incorrect and needs relabeling.

Answer

The change requires a reboot to take effect.

Question 3

A system administrator wants to allow user 'jdoe' to execute any command as root via sudo without being prompted for a password, but only from the host 'client1.example.com'. Which sudoers rule achieves this?

Accepted Answer

jdoe client1.example.com=(root) NOPASSWD: ALL. Option A is correct because the sudoers rule 'jdoe client1.example.com=(root) NOPASSWD: ALL' specifies the user 'jdoe', the host 'client1.example.com' as the source host from which the command is run, the target user '(root)', the NOPASSWD tag to skip password authentication, and the command 'ALL' to allow any command. This matches the requirement exactly: passwordless root access restricted to a specific client host.

Answer

jdoe client1.example.com=(root) ALL

Answer

jdoe ALL=(root) NOPASSWD: ALL

Answer

jdoe ALL=(root) ALL

Question 4

A server's firewall is managed by firewalld. The admin adds a rule to allow HTTPS traffic to the public zone, but clients still cannot connect. What is the most likely cause?

Accepted Answer

The rule was added with --permanent but firewall-cmd --reload was not run.. Option A is correct because when a rule is added with the `--permanent` flag in firewalld, it is written to the configuration files but not applied to the runtime firewall. Until `firewall-cmd --reload` is executed, the runtime configuration remains unchanged, so the new rule allowing HTTPS traffic is not active. Clients cannot connect because the firewall is still blocking HTTPS based on the old runtime rules.

Answer

The rule must be added as a rich rule, not a simple service.

Answer

The default zone is not set to public.

Answer

firewalld is just a wrapper for iptables, so iptables rules must be cleared.

Question 5

Which TWO commands can be used to display SELinux contexts of files? (Choose two.)

Accepted Answer

stat -c %C. The `stat -c %C` command displays the SELinux security context of a file by using the `%C` format specifier, which outputs the security context string. The `ls -Z` command also shows SELinux contexts for files in a directory listing, with the `-Z` flag specifically requesting security context information. Both commands are standard tools for viewing SELinux labels on files.

Answer

chcon -l

Answer

id -Z

Answer

getenforce

Question 6

Which THREE factors determine whether a local user can SSH into a Red Hat Enterprise Linux 9 system? (Choose three.)

Accepted Answer

The user's shell is listed in /etc/shells.. Option C is correct because SSHd validates that the user's login shell is listed in /etc/shells before allowing authentication. If the shell is not present in /etc/shells (e.g., /sbin/nologin or a custom script), SSHd will deny the connection, even if the user has valid credentials. This check is controlled by the 'AllowUsers' and 'DenyUsers' directives but is a fundamental security measure to prevent users with non-standard shells from gaining interactive access.

Answer

The /etc/nologin file exists.

Answer

The user has sudo privileges.

Question 7

Refer to the exhibit. A web server (httpd) is unable to serve files from a user's home directory. What is the most appropriate single command to resolve the issue?

Accepted Answer

semanage fcontext -a -t httpd_sys_content_t '/home/user/www(/.*)?' && restorecon -Rv /home/user/www. Option C is correct because it uses `semanage fcontext` to set the default SELinux file context for the `/home/user/www` directory tree to `httpd_sys_content_t`, then applies it with `restorecon`. This is the proper way to persistently label custom web content directories so that httpd can serve them, as SELinux policy by default blocks httpd from reading user home directories.

Answer

chcon -u system_u /home/user/www/index.html

Answer

setsebool -P httpd_enable_homedirs on

Answer

chcon -r object_r /home/user/www/index.html

Question 8

You are the system administrator for a small company. A developer, Alice, needs to restart the web server (httpd.service) on server 'web1.example.com' without being prompted for a password. She should also be able to run any command as root on that server, but only from the server itself (not remotely). Currently, Alice can SSH into the server using her SSH key, but when she runs 'sudo systemctl restart httpd', she is prompted for her password. You have verified that Alice is in the 'wheel' group. The sudoers file currently has the line '%wheel ALL=(ALL) ALL'. You want to modify sudoers to satisfy the requirement with minimal privilege. Which action should you take?

Accepted Answer

Add 'alice web1.example.com=(root) NOPASSWD: /usr/bin/systemctl restart httpd' to /etc/sudoers.d/alice.. Option B is correct because it grants Alice passwordless sudo access specifically to the command `/usr/bin/systemctl restart httpd` on the host `web1.example.com` as root, meeting the requirement with minimal privilege. The `NOPASSWD:` tag is essential to bypass the password prompt, and the host restriction ensures the rule applies only when Alice is on that server.

Answer

Add 'alice web1.example.com=(root) NOPASSWD: ALL' to /etc/sudoers.d/alice.

Answer

Add 'alice web1.example.com=(root) /usr/bin/systemctl restart httpd' to /etc/sudoers.d/alice.

Answer

Change '%wheel ALL=(ALL) ALL' to '%wheel ALL=(ALL) NOPASSWD: ALL' in /etc/sudoers.

Question 9

A system administrator needs to configure a firewall using firewalld to allow incoming HTTPS traffic and deny incoming SSH traffic from a specific source IP 192.168.1.100. Which two commands should be run? (Choose two.)

Accepted Answer

firewall-cmd --add-service=https --permanent. Option C is correct because `firewall-cmd --add-service=https --permanent` adds the HTTPS service (TCP port 443) to the permanent firewall configuration, which is required to allow incoming HTTPS traffic persistently across reboots. The `--permanent` flag ensures the rule survives a reload or restart, and the `--add-service` option uses predefined service definitions from firewalld to simplify rule creation.

Answer

firewall-cmd --runtime-to-permanent

Answer

firewall-cmd --add-rich-rule='rule family=ipv4 source address=192.168.1.100 service name=ssh reject' --permanent

Answer

firewall-cmd --add-service=http --permanent

Question 10

A junior administrator is tasked with setting up SELinux contexts on a Red Hat Enterprise Linux 9 server to allow Apache HTTPD to read and write to a custom directory /var/www/customcontent. The directory already exists and contains several files. The administrator has confirmed that the httpd service is running and SELinux is in enforcing mode. After changing the context to httpd_sys_content_t using chcon, the web server can read files but cannot write to the directory. The administrator needs to fix this without disabling SELinux or changing the mode to permissive. Which of the following is the correct next step?

Accepted Answer

Run restorecon -R -v /var/www/customcontent after setting the default context with semanage fcontext -a -t httpd_sys_rw_content_t '/var/www/customcontent(/.*)?'. The directory already has the httpd_sys_content_t type, which allows reading but not writing. To enable write access, the correct type is httpd_sys_rw_content_t. Option B correctly uses semanage fcontext to set the default context to this type and then runs restorecon to apply it persistently, ensuring Apache can both read and write.

Answer

Set the SELinux boolean httpd_enable_homedirs to on using setsebool.

Answer

Change the context to httpd_sys_content_t using chcon -R -t httpd_sys_content_t /var/www/customcontent

Answer

Run semanage fcontext -a -t httpd_sys_rw_content_t '/var/www/customcontent(/.*)?' without running restorecon.

Question 11

Order the steps to configure firewall rules to allow HTTP and HTTPS traffic using firewalld.

Question 12

Match each networking term to its definition.

Question 13

A sysadmin wants to allow user 'alice' to run all commands as root via sudo. Which line should be added to /etc/sudoers?

Accepted Answer

alice ALL=(ALL) ALL. Option C is correct because the sudoers entry 'alice ALL=(ALL) ALL' grants user 'alice' the ability to run any command as any user (including root) on any host. The first 'ALL' specifies any host, '(ALL)' allows running commands as any target user (defaulting to root when no user is specified), and the final 'ALL' permits any command. This is the standard syntax for full sudo privileges.

Answer

alice ALL=(root) ALL

Answer

alice localhost=(ALL) ALL

Answer

%alice ALL=(ALL) ALL

Question 14

After configuring sudo, a user reports: 'sudo: unable to open /etc/sudoers: Permission denied'. The admin checks the file permissions and sees '-rw-r-----' owned by root:root. What is the most likely cause?

Accepted Answer

The file permissions are too permissive (0640 instead of 0440).. Option C is correct because the sudoers file requires strict permissions of 0440 (owner read, group read) to be considered secure by sudo. The current permissions of 0640 (owner read/write, group read) are too permissive, as they grant write access to the owner (root), which violates sudo's security model. When sudo detects that /etc/sudoers has permissions other than 0440, it refuses to open the file and reports 'Permission denied' to prevent potential tampering.

Answer

The file is owned by the wrong user.

Answer

The sudo binary is missing the setuid bit.

Answer

SELinux is blocking access.

Question 15

A server uses firewalld with the default zone set to 'drop'. SSH is allowed only for the 192.168.1.0/24 subnet via a rich rule in the 'internal' zone. After a reboot, SSH connections from that subnet are refused. What is the most likely cause?

Accepted Answer

The network interface is not assigned to the 'internal' zone.. After a reboot, firewalld applies the default zone to all interfaces not explicitly assigned to another zone. Since the rich rule allowing SSH from 192.168.1.0/24 is defined in the 'internal' zone, the network interface must be assigned to that zone for the rule to take effect. If the interface is not assigned (e.g., it remains in the default 'drop' zone), all incoming traffic, including SSH from the allowed subnet, is dropped by default.

Answer

The subnet 192.168.1.0/24 is not a valid source for rich rules.

Answer

The rich rule was not made permanent.

Answer

The SSH service is not enabled in the default zone.