702-100 Linux Professional Institute BSD Specialist Questions and Answers

The wq! command is used to save a file and quit the vi editor, even if the file is read-only. The w command means write, the q command means quit, and the ! command means force. By combining these commands, the vi editor will override the file permissions and save the changes to the file, then exit the editor. The other options are either invalid syntax or do not force the write operation. For example, wq will save and quit only if the file is writable, ql will quit without saving, and fw! will force write but not quit. References:

• [vi] - FreeBSD vi(1) Manual Page
• [wq!] - How to save a file in vi / vim editor in Linux / Unix

Compiling an application from source code allows for customization of the binary to a system’s particular needs, including optimization for specific hardware and enabling or disabling certain features. Pre-compiled binaries are quick and easy to install but they don’t allow for such customization.

References:

• Understand the difference between a pre-compiled binary and compiling from source

The command route add default 192.168.1.1 is used to set the default gateway on a BSD system. This command adds a default route to the routing table, directing traffic to the specified gateway IP address when no other route matches.

References:

• FreeBSD Handbook - Routing
• OpenBSD Change, Add or Display Default Gateway

The /etc/fstab file contains information about the file systems that are mounted automatically at boot time or by the mount command. The file has six fields separated by whitespace: device, mount point, file system type, mount options, dump frequency, and pass number. The correct answer is D because it specifies the device (/dev/cd0a), the mount point (/cdrom), the file system type (cd9660), the mount option (ro for read-only), and the dump frequency and pass number (both 0 for no backup or fsck). The other answers are incorrect because they either have the wrong syntax, the wrong order of fields, or the wrong file system type. References:

• BSD Specialist Exam 702 Objectives, Topic 715: Basic Unix Skills, 715.2 File and Directory Management
• FreeBSD Handbook, Chapter 3: FreeBSD Basics, 3.8.2 Mounting and Unmounting File Systems

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 adduser.conf file is used to store the default settings for the interactive adduser script on BSD systems. The adduser script is a shell script that uses the pw command to add new users to the system. It creates passwd/group entries, a home directory, copies dotfiles and sends the new user a welcome message. The adduser.conf file allows the administrator to pre-set certain configuration options, such as the default shell, home partition, login group, encryption method, etc. The other options are either invalid files or belong to other purposes. For example, login.conf is used to define login classes, pw.conf is used to configure the pw command, user.conf is used to set user-specific kernel variables, and usermgmt.conf is used to configure user management utilities. References:

• adduser - FreeBSD adduser(8) Manual Page1
• adduser.conf - FreeBSD adduser.conf(5) Manual Page2
• [pw] - FreeBSD pw(8) Manual Page

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/

The command chown changes the ownership of a file or directory. The syntax is chown user:group file, where user is the new owner and group is the new group of the file. In this case, the superuser can grant the user bob write permission to the file by changing both the owner and the group of the file to bob. This way, bob will have the same permissions as the original owner, which is read and write. Alternatively, the superuser can also use the command chmod to change the permissions of the file without changing the ownership. For example, chmod g+w bobsfile will add write permission to the group, and chmod o+w bobsfile will add write permission to others. However, these commands will also affect other users who belong to the same group or are not the owner or the group of the file. References:

• FreeBSD Handbook: File and Directory Ownership
• FreeBSD Handbook: File and Directory Permissions
• Linux Professional Institute BSD Specialist: 702.1 Filesystem and Devices

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 /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 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 file that defines the IP address of the default gateway on a FreeBSD system is /etc/rc.conf. This file contains various system configuration options, including network settings. To set the default gateway, the defaultrouter variable is used, followed by the IP address of the gateway. For example, defaultrouter=“192.168.1.254”. This setting will be persistent across reboots.

References

• FreeBSD Set a Default Route / Gateway - nixCraft
• Chapter 34. Advanced Networking | FreeBSD Documentation Portal
• Static default gateway on FreeBSD 8.0 - Super User

The last command displays a list of the last logged in users on a BSD system. The output consists of several columns that show the user name, the terminal name, the login date and time, and the logout date and time or the current status. The option C is the only line that matches the format of the last command output. It shows that the user root logged in on the terminal ttyv0 on Saturday, May 18, 2023 at 13:35 and is still logged in. The other options are either invalid lines or belong to othercommands or sources. For example, option A is the output of the uptime command, option B is a line from the /var/log/auth.log file, option D is a line from the ps command, and option E is the output of the uname -a command. References:

• [last] - FreeBSD last(1) Manual Page
• [How to use the last command in Linux] - Linuxize

The sysctl command is used to set and get kernel state variables, including the FreeBSD security level. The security level is a variable named kern.securelevel, which can have values from -1 to 3, with higher values indicating more restrictions. The security level can only be increased, not decreased, unless the system is rebooted or in single-user mode. The security level affects various operations, such as loading kernel modules, changing immutable flags on files, and modifying device nodes12 References: 1: https://docs.freebsd.org/en/books/handbook/security/#security-basics-securelevels  2: https://www.freebsd.org/cgi/man.cgi?query=sysctl &sektion=8

This command and option can be used to perform a reverse DNS lookup, which is the process of finding the domain name or hostname associated with an IP address. The dig command is a tool that can query DNS servers for various types of records, such as A, MX, NS, PTR, etc. The -x option tells dig to perform a reverse DNS lookup by sending a PTR query to the DNS server. For example, to perform a reverse DNS lookup for the IP address 8.8.8.8, the following command can be used:

dig -x 8.8.8.8

The output of this command will show the PTR record for 8.8.8.8, which is dns.google. This means that the hostname for 8.8.8.8 is dns.google. Reverse DNS lookups are useful for verifying the identity of a host, checking for mail server configuration, or troubleshooting network problems