Shell and Kernel
Basically, the kernel is the center of the operating system that manages everything. The shell is just a particular program, a friendly interface that translates your commands into some low-level calls to the kernel. The shell is actually interfaced between user and kernel.
It will run on the first Virtual Console in Red Hat Enterprise Linux 7 five additional text login prompts are available on consoles access a text login prompt on a virtual console be holding Ctrl+Alt and pressing a function key F2 to F6 press Ctrl+Alt+F1/F7 to return to the first virtual console (Graphic Desktop)
Select Applications –> Utilities –> Terminal
|Options||=||To adjust the behavior of the command|
|Arguments||=||Which are typically targets of the command|
# pass[press TAB] [completion]
# pass[press 2 time TAB] [shows possible matches]
[NOTE: Remember All commands are lower-case]
1. The authorization is given to users that enables them to access specific resources on the network, such as data files
– For example, a person who works for a company’s customer service department may be privileged to view a customer’s information otherwise blocked to other employees.
ACLs (Access Control Lists) ACLs allow us to grant permissions for a user, group and any group of any users which are not in the group list of a user.
As a System Admin, our first priority will be to protect and secure data from unauthorized access.
We all are aware of the permissions that we set using some helpful Linux commands like chmod, chown, chgrp… etc. However, these default permission sets have some limitation and sometimes may not work as per our needs. For example, we cannot set up different permission sets for different users on same directory or file. Thus, Access Control Lists (ACLs) were implemented.
Port No. 123
Introduce in 1985.
NTP stands for Network Time Protocol, and it is an internet protocol used to synchronize the clocks of computers to some time reference.
Port forwarding is the process of forwarding requests for a specific port to another host, network, or port. it is considered a type of NAT operation.
NIC Channel Bonding/Teaming
NIC teaming allows multiple network cards to act as one network card.
NIC teaming allowing increased bandwidth and redundancy.
NIC Teaming as Active Backup will provide you redundancy in case of any one of NIC is failed still end user can access services from server. We also call it has Fail-Over mechanism.
What is Kdump?
Starting in Red Hat Enterprise Linux 5, kernel crash dumps are captured using the kdump mechanism. Kexec is used to start another complete copy of the Linux kernel in a reserved area of memory. This secondary kernel takes over and copies the memory pages to the crash dump location.
The Linux “tar” stands for tape archive, The tar command used to rip a collection of files and directories into highly compressed archive file. The tar is most widely used command to create compressed archive files and that can be moved easily from one disk to another disk or machine to machine.
scp and rsync difference
difference is what happens during a transfer retry. While SCP will ignore any partially transferred set of files and overwrite them on the receiving end, rsync is more clever than that. Rsync will check the destination for any files present and if their signature matches that of the files on the sender side
it will not retransmit these files
The MBR (Master Boot Record) is 512 bytes.
– 446 bytes Bootloader
– 64 bytes (4 * 16 bytes) Partition Tables
– 2 bytes Magic Number
sudo = super user do
sudo allows a permitted user to execute a command as the superuser or another user.
Lightweight Directory Access Protocol
Port No:- 389
LDAP is an internet protocol that email and other programs use to look up information from a
server LDAP is mostly used by medium-to-large organization.
– Centralized Authentication
– Network User Login