RHCSA RHCSA Linux Essentials 3

Question 1

Which command shows all active listening TCP and UDP ports with associated process names?

Accepted Answer

ss -tulnp

Answer

`ss -tulnp` shows TCP/UDP listening sockets with numeric addresses and the owning process.

Question 2

You need to create a 2 GiB swap file at /swapfile. What is the correct sequence?

Accepted Answer

dd if=/dev/zero of=/swapfile bs=1M count=2048; chmod 600 /swapfile; mkswap /swapfile; swapon /swapfile

Answer

The full correct sequence creates the file, sets strict permissions (600), formats it as swap, then activates it.

Question 3

Which firewalld command permanently opens port 8080/tcp in the public zone?

Accepted Answer

firewall-cmd --permanent --zone=public --add-port=8080/tcp

Answer

The `--permanent` flag writes the rule to the zone's XML config so it persists after a reload or reboot.

Question 4

What does the `lsblk` command display?

Accepted Answer

Block device tree with mount points and sizes

Answer

`lsblk` lists block devices in a tree format showing name, size, type, and mount point.

Question 5

A cron job entry reads: `*/15 * * * * /script.sh`. How often does it run?

Accepted Answer

Every 15 minutes

Answer

`*/15` in the minute field means 'every 15 minutes' (0, 15, 30, 45).

RHCSA Exam Practice Test