Linux Sys Admin

systemd

What is systemd? systemd consists of these components: systemd, which is the system and service manager systemctl, a command line tool to interact with systemd journald, a unified logging framework logind, a daemon that handles user logins and seats resolved, timesyncd, and networkd, which are responsible for network connection, domain name resolution and synchronizing time with internet resources Managing existing services A service is essentially a process, running in the background and managed/provisioned by systemd.

July 6, 2021 Read

Grub

About Virtually, all x86-based Linux systems (outside the embedded sphere) today use GRUB (GRand Unified Bootloader) to handle the early phases of system startup. Other platforms may have other equivalents, such as ELILO used on EFI systems such as IA64 (Itanium), and Das U-BOOT used on many embedded configurations. Some important features of GRUB are: Alternative operating systems can be chosen at boot time. Alternative kernels and/or initial ramdisks can be chosen at boot time for a given operating system.

April 23, 2021 Read

Kernel

About Linux is only the kernel of the operating system, which includes many other components, such as libraries and applications that interact with the kernel. The kernel is the essential central component that connects the hardware to the software and manages system resources, such as memory and CPU time allocation among competing applications and services. It handles all connected devices using device drivers, and makes the devices available for operating system use.

April 23, 2021 Read

Boot Process

In this post we will take about the boot process of linux OS Stages There are 4 Stages and they are: The Firmware Phase (BIOS and UEFI integrity check) (POST) The Bootloader Phase The Kernel Phase (initialization) Starting Systemd, the parent of all processes Firmware Phase The firmware is the BIOS (Basic Input/Output System) or the UEFI (Unified Extensible Firmware Interface) code that is stored in flash memory on the mother board.

April 22, 2021 Read

Lab Setup

This Post we will focus on building our lab to practice Sys-Admin Tasks. There are multiple ways of setting up the lab with different distro’s. Cloud (AWS,GCP etc) Free tier. Hypervisor (virtual box, Vmware etc) Vagrant (which would use an hypervisor but convenient for ready to use boxs) many more. I will choose Hypervisor(Virtual Box) with my host OS as Kubuntu. Download VirtualBox virtualbox-link select the distribution of your choice and download it.

April 21, 2021 Read

Encryption

Why Use Encryption? Encryption should be used wherever sensitive data is being stored and transmitted. Configuring and using block device level encryption provides one of the strongest protections against harm caused by loss or compromise of data contained in hard drives and other media. Modern Linux distributions offer the choice of encrypting all or some of your disk partitions during installation. It is also straightforward to create and format encrypted partitions at a later time, but you cannot encrypt an already existing partition in place without a data copying operation.

April 18, 2021 Read

Logical Volume Manager

About Logical Volume Manager One or more physical volumes (disk partitions) are grouped together into a volume group. Then, the volume group is subdivided into logical volumes, which mimic to the system nominal physical disk partitions and can be formatted to contain mountable filesystems. Logical volumes are created by putting all the devices into a large pool of disk space (the volume group), and then allocating space from the pool to create a logical volume.

April 18, 2021 Read

Quotas

Filesystem Quotas Linux can use and enforce quotas on filesystems. Disk quotas allow administrators to control the maximum space particular users (or groups) are allowed. Considerable flexibility is allowed and quotas can be assigned on a per filesystem basis. Protection is provided against a subset of users exhausting collective resources. Utilities quotacheck quotacheck generates and updates quota accounting files. quotaon quotaon enables quota accounting. quotaoff quotaoff disables quota accounting.

April 18, 2021 Read

RAID

About RAID Three essential features of RAID are: mirroring: writing the same data to more than one disk striping: splitting of data to more than one disk parity: extra data is stored to allow problem detection and repair, yielding fault tolerance. Thus, use of RAID can improve both performance and reliability. mdadm is used to create and manage RAID devices. Once created, the array name, /dev/mdX, can be used just like any other device, such as /dev/sdb1.

April 18, 2021 Read

swap

About Swap Linux employs a virtual memory system, in which the operating system can function as if it had more memory than it really does. This kind of memory overcommission functions in two ways: Many programs do not actually use all the memory they are given permission to use. Sometimes, this is because child processes inherit a copy of the parent’s memory regions utilizing a COW (Copy On Write) technique, in which the child only obtains a unique copy (on a page-by-page basis) when there is a change.

April 18, 2021 Read

Disk Partition

How to many utilities are available to partition disks , we will be using fdisk to make partitions on disk. # list disks [s0x45ker--_(+_+)_--SysAdmin ~]$ lsblk NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT sda 8:0 0 21.3G 0 disk ├─sda1 8:1 0 1G 0 part /boot └─sda2 8:2 0 20.3G 0 part ├─cl-root 253:0 0 18.3G 0 lvm / └─cl-swap 253:1 0 2.1G 0 lvm [SWAP] sdb 8:16 0 2G 0 disk sr0 11:0 1 1024M 0 rom sr1 11:1 1 1024M 0 rom we will be using /dev/sdb in this tutorial

April 17, 2021 Read

Disk Types

SATA (Serial Advanced Technology Attachment) SATA disks were designed to replace the old IDE drives. They offer a smaller cable size (7 pins), native hot swapping, and faster and more efficient data transfer. They are seen as SCSI devices. SCSI (Small Computer Systems Interface) SCSI disks range from narrow (8 bit bus) to wide (16 bit bus), with a transfer rate between 5 MB per second (narrow, standard SCSI) and 160 MB per second (Ultra-Wide SCSI-3).

April 17, 2021 Read