Operating system basics

Definition of OS:

The operating system is a kind of software that manages the computer hardware and services the programs in it.

Examples:

Windows, Mac, Linux are some of the operating systems.

Basic function:

1.It manages hardware and software resources.

2. It helps in executing the instructions.

3.coordinate between keyboard, printer, etc.

Process:

The process is a kind of program performed in the computer for execution in a sequential manner.

It is divided into 4 sections:

Stack, heap, text, and data.

Memory

Memory refers to internal memory in the computer and it performs and manages allocation, swapping such kinds of things.

· Basically, memory is of two types. Primary memory and secondary memory. Basic levels of memory consist of CPU, cache memory, primary and secondary memory. Memory management is essential for modern computer operation.

File system

The file is the collection of information, records that are stored in secondary memory such as magnetic disks. Based on the ability of an operating system, files are classified as:

1.ordinary files: which contain useful information.

2.Directory files: It consists of a content list of data that are invoked in this particular file.

3.special files: These describe the physical devices. It is also known as device file.

Basic Linux commands

Linux is the entire family of Unix operating systems which is only used by programmers.

Basic Linux commands:

1.pwd command

It is used to find the path of the directory where you’re in.

2.cd command

To navigate through Linux files, we use this command.

3.cat command

It is used to list the contents of the file at standard output. Most frequently used Linux command.

4.mv command

The primary thing is it moves the files and the secondary thing Pure also renames the files.

5.rmdir command

If you want to delete any directory, we use this command.

Managing sudo permission without sudo command:

Sudo is meant for substituting user and do the task. It is basically a Linux program meant for users to use root privileges.

1. If you want to run a sudo command you must contain sudo password. If you want to manage permission without using sudo command then, you need to add that command in the sudoer’s file.

2. In general, some of the Linux operating systems have sudo inbuilt in it. There is no use of sudo command by the user.

3. You cannot execute normal arbitrary admin commands without using sudo.

4. There are some permissions like “ hduser “ to access without sudo command.

5.The permissions are 1 to execute, 4 to read, 2 to write.

When you see a file with permission 644, that means the user can read and write in it . Group and rest of the users can only read it.

5. The command to change the permission is “ chmod “.

6. The permissions are defined from the “ umask “.

Block storage:

Block storage also known as block-level storage that is used to store data files on storage area networks (SAN) or cloud-based storage environments.

It has less than 500 terabytes of data.

It has transactional, structured as well as and unstructured data types which are mainly used in databases and VMFS volumes.

It has a centralized office location.

Object storage

Object storage manages data and links to associated metadata.

It has highly reliable cloud-scale secondary storage.

It has greater than 500 terabytes of data.

It has unstructured data type.

It is mainly used in data backup and big data analytics.

It has centralized and geographically dispersed office locations.

It has on-premises, private, hybrid or public cloud as a storage site.

It has a latency of tolerant data access.

Directory structure of Linux:

The directory structure of Linux looks like a tree. Base of the Linux begins at the root. The directory separator in Linux is the forward slash(/).

1. /-Root

Every file starts from the root itself. Only root user has written privilege under this directory.

2. /bin-user binaries:

It contains binary executables. Common Linux commands used fall under this directory.

3. /sbin-system binaries:

It also contains binary executables. Linux commands located under this directory are used typically by system administrator.

4. /Dev-Device files:

Contains device files. These include terminal devices, usb or any device attached to the system.

5. /proc-process information:

Contains information about system process. It is a virtual file system with text information about system resources.

It is also a pseudo file system contains information about running process.

6. /var-variable files:

Content of the files which are expected to grow fall under this directory.

This includes system log files, packages and database files, emails, print queues, lock files.

These are some of the basic file system examples in the Linux directory structure.