Architectures
RHCE EXAMS based on the basic Intel 32-bit or i386 architecture
Intel Communications Channels
Three basic channels are used to communicate in a basic PC:
1: interrupt request (IRQ) ports --------/proc/interrupts
An IRQ is a signal that is sent by a peripheral device to the CPU to request processing time.
Normally, each device needs a dedicated IRQ (except for USB and some PCI devices).
2: input/output (I/O) addresses --------/proc/ioports
It's a place where data can wait in line for service from your CPU.
3: direct memory address (DMA) channels --------/proc/dma
A direct memory address (DMA) is normally used to transfer information directly between devices like sound cards which include their own processor, bypassing the CPU.
File Filters
sort, grep, egrep,wc, sed, awk
The wc command, short for word count, can return the number of lines, words, and characters in a file.
The sed command, short for stream editor, allows you to search for and change specified words or even text streams in a file.
sed 's/Windows/Linux/g' opsys > newopsys
The awk command, is more of a database manipulation utility. It can identify lines with a keyword and read out the text from a specified column in that line.
awk '/Mike/ {print $1}' /etc/passwd
