RHCE # Week # 278

Question: 

What is the correct location of the Linux Kernel?

A. /boot/vmlinuz
B. /boot/bzImage
C. /boot/kernel
D. /boot/vmlinux


Explanation:


A kernel is a program that constitutes the central core of a computer operating system. It is the first thing that is loaded into memory when a computer is booted up (that is started), and it remains in the memory for the entire time that the computer is in operation.

Linux kernel is dynamic, supporting the addition and removal of software components on the fly.

vmlinuz is the name of the Linux kernel executable. Actually vmlinuz is a compressaed Linux kernel, and it is bootable. Bootable means it is capable of loading the operating system into memory so that the computer becomes usable and application programs can be run.

vmlinuz should not be confused with vmlinux, which is the kernel in a non-compressed and non-bootable form. vmlinux generally just an intermediate step to producing vmlinuz.

vmlinuz is located in the /boot directory, which is the directory that contains the files needed to begin booting the system. The file named vmliuz might be the actual kernel executable itself, or it could be a link to the kernel executable, which might bear a name such as /boot/ vmlinux-2.4.18.8.0 (that is the name of the specific version of the kernel).

Answer:  A

RHCE # Week # 277

Question: 

Fill in the blanks

The _________ service is designed to cron jobs that could not run while a server was powered down.


Explanation:


Anacron is a computer program that performs periodic command scheduling which is traditionally done by cron, but without assuming that the system is running continuously. When executed, Anacron reads a list of jobs from a configuration file, normally /etc/anacrontab. This file contains the list of jobs that Anacron controls. Each job entry specifies a period in days, a delay in minuts, a unique job identifier, and a shell command.

For each job, Anacron checks whether this job has been executed in the last n days, where n is the period specified for that job. If not,Anacron runs the job's shell command, after waiting for the number of minutes specified as the delay parameter.

After the command exits, Anacron records the date in a special timestamp file for that job, so it can know when to execute it again. Only the date is used for the time calculations. The hour is not used.

fcron is another implementation of cron which attempts to fulfill the roles of both Vixiecron and anacron.

fcron is a periodical command scheduler which aims at replacing Vixie Cron, so it implements most of its functionality.

But fcron does not assume that your system is running either all the time nor regularly : we can, for instance, tell fcron to execute tasks every x hours y minutes of system up time or to do a job only once in a specified interval of time.

fcron should be started from /etc/rc or /etc/rc.local

Answer:  Anacron / fcron

RHCE # Week # 276

Question: 

Which of the following run levels runs the system at single user mode?

A. 2
B. 3
C. 1
D. 0


Explanation:

Runlevels define what tasks can be accomplished in the current state (or runlevel) of a Linux system. Every linux system supports three basic runlevels, plus one or more runlevels for normal operation.

Linux Basic Runlevels
Level # Purpose
0 # Shut down or half the system
1 # Single-user mode, usually aliased as s or S
6 # Reboot the system

Other common linux runlevels (usage differs among distributions)
Level # Purpose
2 # Multiuser mode without networking
3 # Multiuser mode with networking
5 # Multiuser mode with networking and the X Window System

Answer:  C