LPIC Level 1 101-500 Exam Questions and Answers PDF

 The signal that is sent by the kill command by default is SIGTERM(15). The kill command sends a signal to a process to terminate it. The signal can be specified by name or number as an option to the kill command. If no signal is specified, the default signal is SIGTERM(15), which means terminate. The process can catch this signal and perform any necessary cleanup before exiting. The SIGHUP(1) signal means hang up and is usually sent when the terminal or network connection is disconnected. The SIGQUIT(3) signal means quit and is usually sent when the user presses Ctrl-\ on the keyboard. The SIGKILL(9) signal means kill and is used to force the process to terminate immediately, without any chance to catch the signal or perform any cleanup. References: LPI Exam 101 Detailed Objectives, Topic 103: GNU and Unix Commands, Weight: 25, Objective 103.3: Perform basic file management, kill command, Signal List

The /etc/inittab file is a plain text file that contains information about the initialization process of the system. It defines the default run level, the available run levels, and the actions to be taken when entering or leaving a run level. The default run level is the mode of operation that the system starts up into, and it determines which services and processes are running. The default run level is specified by a line similar to the following in the /etc/inittab file:

id:5:initdefault:

The number after the first colon indicates the default run level, which can range from 0 to 6. The meaning of each run level is:

• 0 — Halt
• 1 — Single-user text mode
• 2 — Not used (user-definable)
• 3 — Full multi-user text mode
• 4 — Not used (user-definable)
• 5 — Full multi-user graphical mode (with an X-based login screen)
• 6 — Reboot

To change the default run level, edit the /etc/inittab file as root and change the number to the desired run level. For example, to change the default run level to 3, use the following command:

sudo nano /etc/inittab

And change the line to:

id:3:initdefault:

Then save and exit the file. The changes will take effect on the next reboot.

References:

• SysV Init Runlevels - Red Hat Customer Portal
• F.4. SysV Init Runlevels - Red Hat Customer Portal
• init - How can I see or change default run level? - Ask Ubuntu

The correct permissions and ownership for the file /etc/passwd are:

B. -rw-r–r-- 1 root root 531 Jun 5 22:45 /etc/passwd

The /etc/passwd file is a plain text-based database that contains information for all user accounts on the system. It is owned by root and has 644 permissions. The file can only be modified by root or users with sudo privileges and readable by all system users. The permissions and ownership of the file are important for the security and functionality of the system. The permissions and ownership of the file can be viewed by using the ls -l command. For example:

ls -l /etc/passwd

The output of the command will show the following information:

-rw-r–r-- 1 root root 531 Jun 5 22:45 /etc/passwd

The first column shows the permissions of the file, which are composed of 10 characters. The first character indicates the file type, which is - for regular files. The next nine characters indicate the permissions for the user (owner), the group, and the others, respectively. Each set of three characters indicates the read ®, write (w), and execute (x) permissions. A dash (-) means no permission. In this case, the permissions are:

• rw- for the user, which means the user can read and write the file, but not execute it.
• r-- for the group, which means the group can only read the file, but not write or execute it.
• r-- for the others, which means the others can only read the file, but not write or execute it.

The second and third columns show the owner and the group of the file, which are both root. The root user is the superuser or the administrator of the system, who has full access and control over the system. The root group is the primary group of the root user, which usually has no other members.

The fourth column shows the size of the file in bytes, which is 531 in this case. The fifth and sixth columns show the date and time of the last modification of the file, which are Jun 5 22:45 in this case. The last column shows the name of the file, which is /etc/passwd in this case.

The other options are not correct because:

• A. -rw------- 1 root root 531 Jun 5 22:45 /etc/passwd: This option has the wrong permissions for the file. The permissions are 600, which means only the user (root) can read and write the file, and the group and the others have no permissions at all. This would prevent the system users from reading the file, which would cause problems for the login process and other utilities that rely on the file.
• C. -rw-r–r-- 1 1 531 Jun 5 22:45 /etc/passwd: This option has the wrong owner and group for the file. The owner and group are both 1, which is the numeric ID of the user and group. However, the numeric ID of the root user and group is 0, not 1. The user and group with the numeric ID of 1 are usually bin, which is a system user and group that own some system binaries and directories. Thebin user and group should not own the /etc/passwd file, as this would compromise the security and functionality of the system.
• D. -rw------- 1 1 531 Jun 5 22:45 /etc/passwd: This option has both the wrong permissions and the wrong owner and group for the file. The permissions are 600, which means only the user can read and write the file, and the owner and group are both 1, which is the numeric ID of the bin user and group. This would prevent the system users from reading the file, and give the bin user and group full access to the file, which would cause problems for the security and functionality of the system.

The content of the kernel ring buffer is reset when the ring buffer is explicitly reset using the command dmesg --clear or when the system is shut down or rebooted. The kernel ring buffer is a portion of the physical memory that holds the kernel’s log messages. It has a fixed size, which means once the buffer is full, the older logs records are overwritten. The dmesg command-line utility is used to print and control the kernel ring buffer in Linux and other Unix-like operating systems1. The dmesg --clear option clears the ring buffer’s contents, which can be useful for debugging purposes or to free up some memory2. The systemshutdown or reboot also clears the ring buffer’s contents, as the physical memory is reset and the kernel is reloaded3.

The other options are false or irrelevant. The ring buffer is not reset when it is read using dmesg without any additional parameters, as this option only displays the current contents of the buffer without modifying them2. The ring buffer is not reset when a configurable amount of time, 15 minutes by default, has passed, as there is no such time limit for the buffer’s persistence4. The ring buffer is not reset when the kernel loads a previously unloaded kernel module, as this action only affects the kernel’s functionality and not its log messages5. References:

• Dmesg Command in Linux | Linuxize1
• dmesg(1) - Linux manual page2
• Linux Dmesg Command Help and Examples - Computer Hope3
• Lockless Ring Buffer Design — The Linux Kernel documentation4
• Linux Kernel Module Management 101 - Linux.com5