Explanation
The directories that contain start scripts for services on FreeBSD are /usr/rc.d/ and /usr/local/etc/rc.d/. The
/usr/rc.d/ directory contains the system-provided scripts for the base system services, such as cron, sshd, syslogd, etc. The /usr/local/etc/rc.d/ directory contains the scripts for the additional services installed from ports or packages, such as apache, mysql, nginx, etc. These scripts follow the BSD rc.d framework, which allows for fine-grained control and customization of the startup process. The scripts are invoked by the main
/etc/rc script, which sources the /etc/rc.conf file for configuration options
https://docs.freebsd.org/en/articles/rc-scripting/

sysrc
Explanation
The sysrc command is used in FreeBSD and NetBSD to manage system-wide daemon and service settings, including those that are started at boot time. It allows administrators to safely edit system rc files, such as /etc/rc.conf, where services to be started at boot time are specified1.
References:
FreeBSD Handbook – rc.conf
FreeBSD Man Pages – sysrc

Explanation
The -e option of the crontab command opens the current user’s crontab in an editor. The editor used is determined by the environment variables VISUAL or EDITOR. If neither of these variables is set, the default editor is vi. The user can edit the crontab file to add, modify, or delete cron jobs, which are scheduled commands or scripts that run at a specified time or interval. The crontab file has the following format:
minute hour day-of-month month day-of-week command
Each field can be a number, a range, a list, or an asterisk (*), which means all possible values. The command can be any valid shell command or script. For example, the following crontab entry runs the backup.sh script every day at 2:30 AM:
30 2 * * * /home/user/backup.sh
To save and install the crontab file, the user needs to exit the editor. The crontab command will check the syntax of the file and report any errors. If the file is valid, it will be installed and the cron daemon will execute the cron jobs according to the schedule. References:
crontab(1) – Linux manual page
FreeBSD Handbook: 11.6. Scheduling Tasks

Explanation
The command df -h displays the disk space usage of all mounted filesystems in a human-readable format. It shows the size, used, available, and percentage of each filesystem, as well as the mount point. This command can be used to check the local filesystems that are currently mounted.
https://unix.stackexchange.com/questions/24182/how-to-get-the-complete-and-exact-list-of-mounted-filesystems
https://www.tecmint.com/find-mounted-file-systems-in-linux/
https://itslinuxfoss.com/check-filesystem-mounted-linux/

Explanation
The file /boot/loader.conf on OpenBSD is used to specify the kernel image that the bootloader should load.
This file contains various settings that can be used to control the boot process, including kernel parameters and device driver options.
References:
boot(8) – OpenBSD manual pages

/
Explanation

The symbol / is used in the vi editor to start the forward search for a string. It is followed by the string to be searched and then Enter to execute the search. The vi editor highlights the first occurrence of the string after the cursor position. To find the next occurrence of the string in the same direction, press n. To find the previous occurrence of the string in the opposite direction, press N. References:
How to Search to Find a Word in Vim or Vi Text Editor
How can I switch from forward to backward search in Vim?
How To Search in VI Editor
How to Search in Vim / Vi

Explanation
The mailer.conf file is used to configure the mailer programs on a BSD system. It allows the system administrator to replace the default mailer programs, such as sendmail, with alternative ones, such as postfix or exim. The mailer.conf file contains a series of entries, each consisting of a label, an equal sign, and a command. The label is the name of the default mailer program, and the command is the path to the alternative mailer program that will be executed instead. For example, to replace sendmail with postfix, the mailer.conf file should contain the following entries:
sendmail /usr/local/sbin/sendmail send-mail /usr/local/sbin/sendmail mailq /usr/local/sbin/sendmail newaliases
/usr/local/sbin/sendmail hoststat /usr/local/sbin/sendmail purgestat /usr/local/sbin/sendmail The mailer.conf file is read by the mailwrapper program, which is a binary that acts as a wrapper for the mailer programs. The mailwrapper program is installed as /usr/sbin/sendmail and /usr/libexec/sendmail/sendmail, and it invokes the appropriate mailer program based on the mailer.conf file. Therefore, to replace the system MTA with another mail server program, the mailer.conf file needs to be updated with the path to the new MTA.
References:
Chapter 31. Electronic Mail | FreeBSD Documentation Portal
DragonFlyBSD: mta

Explanation
Permissions involve read, write, and execute roles that can be assigned to the owner, a group, or other users1.To use the chmod command, you must specify the permission you want to set and the file or directory you want to modify1.For example,chmod +rwx filenameto add permissions,chmod -rwx directorynameto remove permissions, orchmod +x filenameto allow executable permissions2.
There are two ways to specify the permissions with the chmod command: symbolic notation and numeric notation1.Symbolic notation uses letters and symbols to represent the user classes and the permissions1.Numeric notation uses octal numbers (0-7) to represent the permissions for each user class1.Each octal digit corresponds to a combination of read , write (w), and execute (x) permissions, as shown in the table below3:
Octal digit
Binary representation
Permissions
0
000
–
1
001
-x
2
010
-w-
3
011
-wx
4
100
r-
5
101
r-x
6
110
rw-
7
111
rwx
To use numeric notation, you need to provide three octal digits, one for each user class (owner, group, and others)1.For example,chmod 644 filenamemeans that the owner has read and write permissions (6), the group has read permissions (4), and others have read permissions (4)1.
In this question, the desired permission for the file text.txt is 750, which means that the owner has read, write, and execute permissions (7), the group has read and execute permissions (5), and others have no permissions (0)1. Therefore, the correct chmod command to change the permission of the file text.txt to 750 ischmod text.txt 750.
References:1: Chmod Command in Linux (File Permissions) | Linuxize2: How to change directory permissions in Linux | Pluralsight3: How to Use the chmod Command on Linux – How-To Geek

Explanation
The cron job syntax consists of five fields that specify the time and date of execution, followed by the command or script to run. The fields are: minute, hour, day of month, month, and day of week. Each field can have a specific value, a range, a list, a wildcard (), or a step value. The wildcard () means any possible value for that field. The option B sets the minute field to 0 and the hour field to *, which means the script will run at the 0th minute of every hour, regardless of the day, month, or weekday. This is equivalent to once per hour.
The other options are either invalid syntax or do not match the desired frequency. For example, option A sets all fields to *, which means the script will run every minute of every hour of every day, month, and weekday.
Option C sets the minute field to * and the hour field to 0, which means the script will run every minute of the
0th hour, or once per day at midnight. Option D has a typo (o instead of *) and option E sets the day of month field to o, which is not a valid value. References:
crontab – FreeBSD crontab(5) Manual Page1
Crontab Explained in Linux [With Examples] – Linux Handbook2

Explanation
The command locate.updatedb updates the database used by locate to find files. The locate command searches for files by name in a pre-built database of files and directories. The database is usually updated periodically by a cron job, but the locate.updatedb command can be used to manually update it. The command may require root privileges to run, depending on the system configuration. References:
BSD Specialist Exam 702 Objectives, Topic 715: Basic Unix Skills, 715.4 Searching and Extracting Data from Files FreeBSD Handbook, Chapter 7: Finding and Installing Software, 7.2.3 Using locate(1) to Find Files Quickly

/etc/hostname.em0
Explanation
The file /etc/hostname.em0 contains the configuration for the network interface em0 on an OpenBSD system.
This file specifies the IP address, netmask, gateway, and other options for the interface. The file is read by the netstart script during boot or when the interface is restarted. The file name is derived from the interface name, which is usually based on the driver name and the device number. For example, em0 is the first interface using the em driver, which supports Intel PRO/1000 network adapters.
References:
Networking | OpenBSD Handbook
[hostname.if(5) – OpenBSD manual pages]

Explanation
The nice command is used to run a command with a modified scheduling priority, which affects how much CPU time the command receives. The priority can be specified by the -n option, which takes an integer value between -20 and 19, where lower values indicate higher priority. By default, the nice value is incremented by
10, which means the command runs with lower priority than normal. Only the superuser can specify a negative increment, which means the command runs with higher priority than normal. For example, the command nice
-n 5 date runs the date command with a priority of 5, while the command nice -n -10 ls runs the ls command with a priority of -10, but only if the user is the superuser. The nice command is useful for running CPU-intensive commands that do not need to finish quickly, or for running commands that need more CPU time than normal. References:
nice – FreeBSD, the manual page for the nice command on FreeBSD.
HowTo: Use ps, kill, nice, and killall To Manage processes in FreeBSD and OS X Unix Operating System – nixCraft, a tutorial on how to use the nice command and other process management commands on FreeBSD and OS X.

Explanation
The command pkg upgrade is used to update FreeBSD packages to newer versions. It compares the versions of installed packages with those in the repositories and performs upgrades as necessary. The pkg update command is used to update the repository catalog, but it does not perform the actual package upgrades1.
References:
FreeBSD Handbook – Packages and Ports

Explanation
According to the BSD disklabel documentation1, the device name for a BSD disk slice consists of three parts:
the disk name, the partition letter, and the slice number. The disk name is determined by the driver and the order of detection, and it usually follows the pattern of sdX, where X is a letter from a to z. The partition letter is a lowercase letter from a to p, excluding c, which is reserved for the whole disk. The slice number is a decimal number from 0 to 15, indicating the MBR partition that contains the BSD disklabel. Therefore, the device name for the first BSD disk slice in the disk label on the first partition on the second SATA disk on OpenBSD is /dev/sdlp2d, where sdl is the disk name, p is the partition letter, and 2 is the slice number.
References1: BSD disklabel – Wikipedia

Explanation
The tar command is used to create or extract compressed archive files on BSD systems. It can handle various compression formats, such as gzip, bzip2, xz, and lzma. The tar command takes different options to specify the compression type, such as -z for gzip, -j for bzip2, -J for xz, and -Z for lzma. The other options are not related to compression, but to other functions of the tar command, such as -x for extracting, -c for creating, and -v for verbose output. References:
[tar(1) – OpenBSD manual pages]
[FreeBSD Handbook – Chapter 3. Unix Basics]
[FreeBSD Handbook – Chapter 18. Storage]

Explanation
The inetd.conf file is the configuration file that needs to be edited before the TFTP service will start on a BSD system. The inetd daemon handles the TFTP service and other network services, and its configuration file contains settings that determine howthese services are managed. To enable the TFTP service, the corresponding entry in inetd.conf must be uncommented and properly configured. References:
FreeBSD Handbook – inetd
Linux Professional Institute BSD Specialist Exam Objectives

Explanation
The command pkg_add is used to install binary packages on OpenBSD systems. It is a utility for installing and upgrading software packages from binary files. When using pkg_add, the system will fetch and install the specified package, along with any dependencies it may have123.
References:
OpenBSD manual pages – packages(7)
nixCraft – OpenBSD install or add binary software package using pkg_add