sca_sles15 Questions and Answers

If you have a service named tftp, the command and options that would enable tftp to start automatically when the server starts are systemctl enable tftp. This command will create symbolic links in the appropriate systemd target directories to enable the tftp service unit. To start the service immediately, you can also use systemctl start tftp or systemctl enable --now tftp. References:https://documentation.suse.com/sles/15-SP3/html/SLES-all/cha-systemd-services.html#sec-systemd-enable

https://documentation.suse.com/sles/12-SP4/html/SLES-all/cha-security-acls.html

The three permissions available on posix file systems are read, write, and execute. The read permission allows the user to view the contents of a file or directory. The write permission allows the user to modify or delete a file or directory. The execute permission allows the user to run a file as a program or change into a directory. References:https://documentation.suse.com/sles/15-SP3/html/SLES-all/sec-file-permissions.html#sec-file-permissions-types

The commands that can be used to terminate processes are kill and killall. The kill command can be used to send a signal to a process specified by its process ID (PID). The default signal is SIGTERM, which requests a graceful termination of the process. The killall command can be used to send a signal to one or more processes specified by their name. It will match all processes that belong to the current user unless otherwise specified. References:https://documentation.suse.com/sles/15-SP3/html/SLES-all/sec-cli-processes.html#sec-cli-processes-kill

The command that allows you to create an alias command is alias. The alias command can be used to define a short name or abbreviation for another command or sequence of commands. The syntax of the alias command is alias name=‘command’. For example, alias c=‘clear’ will create an alias named c for the clear command. You can then type c to run the clear command. To remove an alias, you can use unalias name. References:https://documentation.suse.com/sles/15-SP3/html/SLES-all/cha-bash.html#sec-bash-alias

The types of files that are used for inter-process communications are pipe and socket files. Pipe files are used for unidirectional data flow between two processes. They can be created with the mkfifo command or with the | operator in a shell command. Socket files are used for bidirectional data exchange between processes on the same or different machines. They can be created with various system calls or commands depending on the protocol and domain. References: https://documentation.suse.com/sles/15-SP3/html/SLES-all/sec-cli-pipes.html https://documentation.suse.com/sles/15-SP3/html/SLES-all/sec-cli-sockets.html

The basic components of RPM are RPM Database and RPM Package Manager. The RPM Database is a collection of files that store information about installed packages on the system. It is located in /var/lib/rpm by default. The RPM Package Manager is a set of tools and libraries that allow you to install, uninstall, query, verify, and manage RPM packages. It includes commands such as rpm, zypper, yast2, etc. References:https://documentation.suse.com/sles/15-SP3/html/SLES-all/cha-rpm.html#sec-rpm-components

https://documentation.suse.com/sles/12-SP4/html/SLES-all/cha-grub2.html

To add two new custom items to the GRUB2 boot menu, you should modify the /boot/grub2/custom.cfg file. This file can contain custom menu entries that will be added to the end of the GRUB2 menu. The syntax and format of this file are similar to /boot/grub2/grub.cfg file. You do not need to run grub2-mkconfig after modifying this file. References:https://documentation.suse.com/sles/15-SP3/html/SLES-all/sec-grub2-custom.html

The scripts in the /etc/grub.d directory are used to generate the /boot/grub2/grub.cfg file and are taken as input by the grub2-mkconfig command. The /boot/grub2/grub.cfg file contains the menu entries and settings for the GRUB2 boot loader. The grub2-mkconfig command is used to create or update this file based on the scripts in /etc/grub.d and other configuration files. The scripts in /etc/grub.d are executed in numerical order and can be customized by the user or administrator. References:https://documentation.suse.com/sles/15-SP3/html/SLES-all/sec-grub2-config.html#sec-grub2-config-files

To make the third menu entry of your GRUB2 boot menu your default menu selection, you need to do the following tasks:

• Edit the /etc/default/grub file and set GRUB_DEFAULT to 2
• Run the grub2-mkconfig command

The /etc/default/grub file contains various settings for the GRUB2 boot loader, such as the default menu entry, the timeout value, the theme file, etc. The GRUB_DEFAULT setting can be set to a numeric value that corresponds to the menu entry index (starting from 0), or a string value that matches the menu entry title. The grub2-mkconfig command will generate a new /boot/grub2/grub.cfg file based on the settings in /etc/default/grub and other configuration files and scripts. References: https://documentation.suse.com/sles/15-SP3/html/SLES-all/sec-grub2-config.html#sec-grub2-config-default

The statement that is true regarding VFS is that VFS is an abstraction layer in the kernel that provides the same interface to applications and users regardless of which file system format is used. VFS stands for Virtual File System or Virtual File System Switch. It allows different types of file systems (such as ext4, xfs, nfs, etc.) to be accessed through a common set of system calls and functions. VFS also provides caching and buffering mechanisms to improveperformance and reliability. References: https://documentation.suse.com/sles/15-SP3/html/SLES-all/sec-vfs.html

The command that is used to ensure an ext3 file system is checked every 50 times it is mounted is tune2fs. The tune2fs command can be used to adjust various parameters of an ext2, ext3, or ext4 file system. The -c option can be used to set the maximum number of mounts between two file system checks. For example, tune2fs -c 50 /dev/sda1 will set the check interval to 50 mounts for /dev/sda1. References:https://documentation.suse.com/sles/15-SP3/html/SLES-all/sec-tune2fs.html

For programs to leverage PolKit they are split into two separate processes. The statements below that are true regarding these two PolKit processes are:

• The Mechanism process runs in the System Context.
• The Policy Agent process runs in the User Session.

The Mechanism process is responsible for performing privileged actions on behalf of unprivileged users. It runs as root in the System Context and communicates with PolKit via D-Bus. The Policy Agent process is responsible for requesting authorization from users when they attempt to perform privileged actions. It runs as a normal user in the User Session and communicates with PolKit via D-Bus. References: https://documentation.suse.com/sles/15-SP3/html/SLES-all/sec-polkit.html#sec-polkit-processes

SUSE Linux Enterprise Server supports two different kinds of VNC sessions: One-time sessions that “live” as long as the VNC connection from the client is kept up, and persistent sessions that “live” until they are explicitly terminated.

5.1 One-time VNC Sessions

5.2 Persistent VNC Sessions

https://documentation.suse.com/sles/11-SP4/html/SLES-all/cha-vnc.html#:~:text=SUSE%20Linux%20Enterprise%20Server%20supports,until%20they%20are%20explicitly%20terminated .

The program systemd is the process with process ID 1. It is responsible for initializing the system in the required way. systemd is started directly by the kernel and resists signal 9, which normally terminates processes. All other programs are either started directly by systemd or by one of its child processes.

The system initialization system used in SLES 15 is systemd. It is a modern and powerful system and service manager that replaces the traditional init system. It provides faster boot times, better dependency handling, parallelization, and more features and capabilities. References:https://documentation.suse.com/sles/15-SP3/html/SLES-all/cha-systemd-basics.html

Firewalld uses two separated configuration sets, runtime, and permanent configuration.

The runtime configuration is the actual running configuration and it is not persistent on reboots. When the firewalld service starts it loads the permanent configuration which becomes the runtime configuration.

https://www.supportsages.com/everything-you-need-to-know-about-firewalld/#:~:text=Firewalld%20uses%20two%20separated%20configuration,which%20becomes%20the%20runtime%20configuration .

Firewalld maintains two separate configurations: runtime and permanent. The runtime configuration is the current state of the firewall that is applied to the system. It can be changed by various commands and tools without affecting the permanent configuration. The permanent configuration is the persistent state of the firewall that is stored in configuration files. It can be changed by various commands and tools with the --permanent option. The permanent configuration will take effect after reloading firewalld or rebooting the system. References:https://documentation.suse.com/sles/15-SP3/html/SLES-all/sec-firewall-firewalld.html#sec-firewall-firewalld-config

The valid device types are character and block devices. Character devices are devices that transfer data byte by byte, such as keyboards, mice, terminals, etc. Block devices are devices that transfer data in fixed-size blocks, such as disks, CD-ROMs, etc. Pipe, null, redirect, udev, and network are not device types but rather concepts or components related to devices or device management. References:https://documentation.suse.com/sles/15-SP3/html/SLES-all/sec-devices.html