Patch Cord Cable

Cable Configuration


Straight : B-Core
1 2 3 4 5 6 7 8
OW Ora GW Blue BW G BrownWh Brown

Straight : A-Core
1 2 3 4 5 6 7 8
GW Green OW Blue BW Orange BW Brown


Note:
OW -> Orange White
GW -> Green White
BW -> Blue White


Method:
Nowadays B-B type straight cable are using
A-A type not in field
Cross:
A - B
B - A

Linux File System

File Permission

File Permission
File

• Owner

• Group

• Other user

Permission mode

• Symbolic

• Absolute

Permissions Symbolic absolute

read r 4

write w 2

execute x 1

readwrite rw 6

readexec rx 5

writeexec wx 3

readwriteexec rwx 7

no access - 0

File Permission Structure

1 2 3 4 5 6 7 8 9 10 These are fields

Type of file --> 1

Owner permission --> 2, 3, 4

Group permission --> 5, 6, 7

Other user permission --> 8, 9, 10

Commands

Syntax

1. #useradd --> if you want to make a user with desire uid, gid etc

(or) #useradd –u -g

-G -d -s

-C loginname

2. #groupadd

(or)

# groupadd –g

3. #passwd

(or)

#passwd –d

Explanation

/etc/group :

If

Backup : x : 502 : secondary users specification

If u create a user with useradd, it will generate 7 fields auto.

Ex: for useradd

#user add –u 1000 –g backup –G print, flag

-d/raj -c “supersuer “ raj

The above line create what our desire user with name of raj

• If u create a userid with 500 means, next one is 502

• Then it will check to create next one means, It will choose the largest group id & make to add +1

Commands

#id sai --> give gid & uid

#finger sai --> It will show all details about user sai

#user del sai --> remove all details frm /etc/group, shadow & passwd… But

/home/sai & /var files are existing

#user del -r sai --> delete sai from entire file system

#passwd sai--> set password (/etc/shadow)

#passwd –d sai --> remove password ’’

#pwconv --> It updates detail from /etc/passwd to /etc/shadow, /etc/shadow is read-only

#passwd –l sai --> To lock a passwd for sai

#passwd –u sai --> To unlock a passwd for sai

#usermode –s /bin/nologin sai --> to change the shell lever from default one /bin/bash to /bin/nologin. Then sai will not login into system. He blocked

No Login

To lock (ie) nologin to all user except root to make file

To create

# touch /etc/nologin

To remove

# rm –rf /etc/nologin

[Note: If you want to protect particular user, go to /etc/passwd file and enter “exclamation mark” at end of that particular user.]

Benefit for Boot loader passwd

If u want to change root’s passwd, you cant enter into linux with single user mode and change it

Steps:

1. Switch on the system

2. press ’e’ (i.e.) it shows on the screen

3. Enter into kernel………. Like ths

But you set bootloader (Grub) passwd, you will not enter inot root’s section directly.

Do it first

#grub –mds-crypt --> This makes encryptions files.

• Boot passwd also available (or) grub

• OS passwd also available

How to set OS passwd?

It’s set only after the Installed,

Go to #/boot/grub/grub.conf

Enter the OS passwd below the title menu

• If you want to set encrypted passwd to grub or OS, you can use

#grub-mds-crypt file & copy the result set to grub

Password=msd-result of crypt

{ Below the splash ing }

Password—mds result of crypt for grub passwd

Linux Basic

Introduction level & commands

Commands

Vi Editor or Emacs Editor (Which is powerful one)

User administration

File permission

Bash configuration

Printer Configuration

Managing process

Find -Methods

Linux File Sysytem Indepth

Net work Clients

USER ADMINISTRATION

Commands
useradd

userdel

user mod

groupadd

groupmod

passwd

pwconv

id

finger

Files

1. /etc/passwd

2. /etc/group

3. /etc/shadow

User Account Information

• User id

• Login name

• Group id (primary and secondary)

• Password

• Home dir path

• Shell

• Comment

Linus Torvalds Quotes

"Any program is only as good as it is useful"

Talk is cheap. Show me the code.

Richard Matthew Stallman's Quote

"Once GNU is written, everyone will be able to obtain good system software free, just like air."


"People said I should accept the world. Bullshit! I don't accept the world."


"I'm always happy when I'm protesting"

"Playfully doing something difficult, whether useful or not, that is hacking"