702-100 Linux Professional Institute BSD Specialist Question and Answers

A /24 IPv4 prefix provides 256 IP addresses, which is the number of addresses in one octet (2^8). A /28 subnet has 16 IP addresses (2^4). To calculate how many /28 subnets can fit into a /24 prefix, divide the total number of addresses in the /24 prefix by the number of addresses in a /28 subnet: 256 / 16 = 16. However, since each subnet has network and broadcast addresses that cannot be used for hosts, the actual number of usable subnets is less. In practice, you can create 16 subnets, each with 14 usable IP addresses for hosts.

References:

• Subnet Cheat Sheet
• IP Subnet Calculator

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

 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

In FreeBSD, theunamecommand is used to display system information. The option-vspecifically displays the version of the running operating system. This information is critical for system administrators and users who need to know the exact version of the OS they are working with, particularly when troubleshooting, updating, or configuring the system for specific software requirements.

https://man.freebsd.org/cgi/man.cgi?query=uname &sektion=1&format=html

The -v or --version option of the uname command displays the version level of the operating system. This is a string that identifies the release date and patch level of the system. For example, on FreeBSD, the output would be something like:

FreeBSD 13.0-RELEASE-p4 #0: Tue Aug 24 07:12:34 UTC 2021

This indicates that the system is running FreeBSD 13.0, with the fourth patch applied, and that the kernel was built on August 24, 2021. The version level can be useful to determine the compatibility and security of the system, as well as to report bugs or issues.

The find command is used to search for files and directories that match certain criteria. The - -type option specifies the type of file to look for, and the d argument means directories. The . argument means the current directory. Therefore, the command find - -type d searches for all directories within the current directory. The other options are either invalid or do not match the question. References: 1: https://www.comptia.org/training/books/a-core-1-220-1101-study-guide, page 301  2: https://www.howtogeek.com/771399/how-to-use-the-find-command-in-linux/, section “The Linux find Command”

The command netcat is a versatile networking utility that can be used to read from and write to network connections using TCP or UDP protocols. It is often used for debugging and investigating the network and can be used to connect to a remote TCP service.

References:

• BSD Specialist Exam 702 Objectives - Linux Professional Institute
• FreeBSD Handbook - Networking

The date command in BSD systems provides the following features:

• It outputs the time in a specific format. The date command can display the current date and time in various formats, depending on the options and arguments given. For example, the command date +%Y-%m-%d will output the date in the format of year-month-day, such as 2023-04-30. The command date +%T will output the time in the format of hour:minute:second, such as 22:51:42. The command date +%A will output the full name of the weekday, such as Thursday. The date command supports many formatting characters that can be used to customize the output. For a full list of formatting characters, see the date(1) manual page1.
• It sets the clock to a specific time. The date command can also be used to set the system date and time, if the user has the appropriate privileges. For example, the command date 0430225123 will set the date and time to April 30, 2023, 22:51:42. The command date -u 0430225123 will set the date and time to the same value, but in UTC (Coordinated Universal Time) instead of the local time zone. The command date -n will set the date and time to the current network time, using the ntpd(8) daemon1.

The date command does not provide the following features:

• It does not display a calendar. The date command only displays the date and time, not a calendar. To display a calendar, the cal(1) or ncal(1) commands can be used instead. For example, the command cal 4 2023 will display the calendar for April 2023. The command ncal -w 2023 will display the calendar for the whole year 2023, with week numbers23.
• It does not send NTP queries. The date command does not send any network requests or queries to NTP (Network Time Protocol) servers. To synchronize the system clock with NTP servers, the ntpd(8) daemon or the ntpdate(8) utility can be used instead. For example, the command ntpd -q will query one or more NTP servers and adjust the system clock accordingly. The command ntpdate pool.ntp.org will set the date and time to the value returned by the NTP server pool.ntp.org45.
• It does not change the system’s timezone. The date command does not change the system’s timezone setting, only the date and time values. To change the system’s timezone, the tzsetup(8) utility or the ln(1) command can be used instead. For example, the command tzsetup will run an interactive program that allows the user to select a timezone from a list of regions and cities. Thecommand ln -sf /usr/share/zoneinfo/Europe/Paris /etc/localtime will create a symbolic link from the file /etc/localtime to the file /usr/share/zoneinfo/Europe/Paris, which contains the timezone information for Paris, France . References:
• date(1) - FreeBSD
• cal(1) - FreeBSD
• ncal(1) - FreeBSD
• ntpd(8) - FreeBSD
• ntpdate(8) - FreeBSD
• [tzsetup(8) - FreeBSD]
• [ln(1) - FreeBSD]

The question mark (?) is a special character in regular expressions that modifies the preceding expression to match zero or one times. For example, the regular expression colou?r matches both color and colour, but not colouur or colr. The question mark is also used to make an expression non-greedy, meaning that it will match the shortest possible string instead of the longest. For example, the regular expression <.?> matches the first pair of angle brackets in a string, while <.> matches the entire string enclosed by the outermost pair of angle brackets. References:

• Regular expression - Wikipedia, section “Basic concepts”
• How to write Regular Expressions? - GeeksforGeeks, section “Special Characters”

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

The ports collection on FreeBSD is a package management system that allows users to install third-party software from source or binary packages. The ports collection is stored in the /usr/ports/ directory, which contains subdirectories for different categories of software, such as archivers, databases, editors, etc. Each subdirectory contains one or more ports, which are directories that contain the files needed to build and install the software. The /usr/ports/ directory can be updated with the portsnap command34

Binary packages are pre-compiled versions of the ports that can be installed with the pkg command. Binary packages are downloaded from the FreeBSD package repository,which is hosted at pkg.freebsd.org. The packages are installed in the /usr/local/ directory by default, and the information about the installed packages is stored in the /usr/local/pkg/ directory. The /usr/local/pkg/ directory contains files with the .db extension, which are SQLite databases that store the metadata of the packages. The pkg command can query and manipulate these databases56 References: 3: https://docs.freebsd.org/en/books/handbook/ports/  4: https://www.freebsd.org/ports/  5: https://docs.freebsd.org/en/books/handbook/pkgng-intro/  6: https://www.freebsd.org/cgi/man.cgi?query=pkg &sektion=8

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]

The zpool create command is used to initialize ZFS on one or more block devices and create a storage pool. A storage pool is a collection of devices that provide physical storage and data replication for ZFS datasets. The zpool create command takes the name of the pool and the devices to be added as arguments. For example, zpool create mypool c0t0d0 c0t1d0 c0t2d0 would create a pool named mypool with three devices. The other options are either invalid or do not initialize ZFS. References: 1: https://www.comptia.org/training/books/a-core-1-220-1101-study-guide, page 302  2: https://docs.oracle.com/cd/E19253-01/819-5461/gbchx/index.html, section “Creating a ZFS Storage Pool”

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

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

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-in-linux

https://www.tecmint.com/find-mounted-file-systems-in-linux/

https://itslinuxfoss.com/check-filesystem-mounted-linux/