How unit 1 is examined
This unit covers what Unix/Linux is, how it is installed and what hardware it needs, why it is popular, and the kernel with its functions. No past question has been asked on any topic, so all eight are short.
Concepts
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Definition. <mark>Unix/Linux is a multi-user, multitasking, portable operating system in which everything is treated as a file and users work through a shell.</mark>
Key points.
- Unix was developed at AT&T Bell Labs in 1969 by Ken Thompson and Dennis Ritchie and was rewritten in C, which made it portable.
- Linux is a free, open-source Unix-like kernel written by Linus Torvalds in 1991 and combined with GNU tools.
- The system has three layers: hardware, the kernel, and the shell with user programs.
- Files are arranged in a single hierarchical directory tree that starts at the root
/.
Unix/Linux Installation Process
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Definition. <mark>Installation copies the operating system from a bootable medium onto a disk partition and configures it for use.</mark>
Key points.
- Boot from a CD, DVD or USB image and choose the language, keyboard and time zone.
- Partition the disk; the minimum is a root
/partition and a swap partition, and/homeis often kept separate. - Select the software packages, set the root password, and create a normal user account.
- Install the boot loader (GRUB) so the system can start, then reboot into the new system.
Hardware Requirements for Unix/Linux
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Definition. <mark>Hardware requirements are the minimum processor, memory and disk resources needed to install and run the system.</mark>
Key points.
- A basic text-mode Linux runs on a modest processor, while a graphical desktop needs a faster one.
- RAM needed is about 128 MB for text mode and 1 GB or more for a desktop.
- Disk space is a few GB for a minimal install and 10 GB or more for a full system, plus a swap partition.
- A keyboard, a display, and a CD/DVD drive or USB port for booting are also needed; Linux supports most standard hardware.
Advantages of Unix/Linux
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Definition. <mark>The advantages of Unix/Linux are the benefits it offers over other operating systems in cost, security, stability and flexibility.</mark>
Key points.
- Linux is free and open source, so there is no licence cost and anyone can modify the code.
- It is secure, because of file permissions, user separation and few viruses.
- It is stable and reliable, and servers can run for years without a reboot.
- It is portable, and works well as a multi-user network server.
Reasons for Popularity and Success of Linux/Unix Operating System
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Definition. <mark>Unix/Linux is popular because it is free, portable, powerful and supported by a large community.</mark>
Key points.
- Being written in C, it was easy to port to many kinds of hardware.
- Linux is free and its source is open, so many developers and companies improve it.
- It offers multi-user, multitasking operation with good networking, which suits servers.
- Its stability, security and many free tools made it the leading choice for servers, supercomputers and Android.
Features of Linux/Unix Operating System
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Definition. <mark>The features of Unix/Linux are its multi-user, multitasking, portable, file-based and secure design.</mark>
Key points.
- It is multi-user and multitasking, so many users and programs run at the same time.
- It is portable and open source, running on many machines.
- The shell gives a command interpreter and scripting, and pipes and redirection join small tools together.
- It has a hierarchical file system in which devices are also files, and it protects files with permissions.
Kernel
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Definition. <mark>The kernel is the core of the operating system that runs in privileged mode and sits between the hardware and the user programs.</mark>
Key points.
- It is loaded into memory at boot and stays there until shutdown.
- Users do not use it directly; they use the shell, which calls the kernel through system calls.
- Linux has a monolithic kernel, in which all services run in one address space.
- Kernel mode has full hardware access, while user programs run in the restricted user mode.
Kernel Functions
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Definition. <mark>Kernel functions are the services the kernel provides: managing processes, memory, files and devices.</mark>
Key points.
- Process management creates, schedules and terminates processes and shares the CPU among them.
- Memory management allocates and frees memory and provides virtual memory and swapping.
- File system management organises files and directories and controls access to them.
- Device management controls hardware through drivers, and the kernel also provides system calls, networking and security.
Last-minute revision
- Unix was created at AT&T Bell Labs in 1969 by Thompson and Ritchie and rewritten in C.
- Linux was written by Linus Torvalds in 1991 and is free and open source.
- Unix/Linux is multi-user, multitasking and portable.
- Everything in Unix is a file, arranged in a tree from root
/. - Installation steps are boot, partition (root and swap), select packages, set the root password, and install GRUB.
- Text-mode Linux needs about 128 MB of RAM and a desktop needs 1 GB or more.
- The system layers are hardware, kernel, and shell with applications.
- Linux has a monolithic kernel.
- Kernel functions are process, memory, file and device management.
- The shell reaches the kernel through system calls.
Memory hooks
- Layers: H-K-S, hardware, kernel, shell.
- Kernel functions: P-M-F-D, process, memory, file, device.
- Installation: BPSRG, boot, partition, select, root password, GRUB.
- Linux is free like air: free, open, everywhere.
Coverage checklist
- Concepts: no past questions.
- Unix/Linux Installation Process: no past questions.
- Hardware Requirements for Unix/Linux: no past questions.
- Advantages of Unix/Linux: no past questions.
- Reasons for Popularity and Success of Linux/Unix Operating System: no past questions.
- Features of Linux/Unix Operating System: no past questions.
- Kernel: no past questions.
- Kernel Functions: no past questions.