Belajarlah berdiri dahulu sebelum cuba untuk berlari.

Definisi Encryption

Encryption adalah penukaran data ke dalam borang, disebut ciphertext.
iaitu bahasa yang tidak difahami oleh orang yang tidak sah.
Dencryption adalah proses menukarkan data yang di encrypt ke bentuk asal.
iaitu dari bahasa yang tidak difahami oleh org lain ke bahasa yang difahami.

Command for LINUX..

arch

arch is deprecated command since release util-linux 2.13.

Use uname -m.

On current Linux systems,

arch prints things such as "i386","i486","i586",

"alpha","sparc","arm","m68k","mips","ppc".

Apa itu LINUX..?

• Linux biasanya diucapkan dalam bahasa Bahasa Inggeris Amerika, juga diucapkan LIN-ooks  di Eropah) adalah keluarga sistem komputer operasi mirip UNIX yang menggunakan kernel Linux. 
• Linux boleh dipasang pada berbagai perkakasan komputer, mulai dari telefon, komputer tablet dan video game konsol, untuk mainframe dan supercomputer. Linux adalah Suatu sistem pelayan terkemuka operasi, dan menjalankan superkomputer tercepat di dunia.

Pembangunan Linux 

1. Nama "Linux" berasal dari kernel Linux, asalnya ditulis pada tahun 1991 oleh Linus Torvalds.
2. Pendukung utama pengguna aplikasi-aplikasi sistem ruangan dan perpustakaan dari projek GNU (diumumkan pada tahun 1983 oleh Richard Stallman) merupakan asas untuk nama pilihan Free Software Foundation GNU / Linux.
3. Adalah salah satu contoh yang paling menonjol dari kolaborasi free dan open source software, biasanya semua kod sumber boleh digunakan, tidak diubahsuai, dan disebarkan, baik komersil dan non-komersial, oleh siapapun di bawah lesen seperti GNU Lesen Awam Am.  
4. Biasanya Linux dikemas dalam format yang dikenali sebagai edaran Linux untuk kegunaan desktop dan server. Beberapa mainstream popular edaran Linux termasuk Debian (dan turunannya seperti Ubuntu), Fedora dan openSUSE. 
5. Linux termasuk kernel Linux dan peralatan penunjang dan perpustakaan untuk memenuhi digunakan edaran itu. 
6.  Sebuah pengedaran berorientasikan pada penggunaan desktop mungkin termasuk X Window System, GNOME dan KDE Plasma persekitaran desktop. 
7. Distro lain mungkin termasuk desktop sumber daya kurang intensif seperti LXDE atau XFCE untuk digunakan pada komputer lama atau kurang-kuat. Sebuah pengedaran bertujuan untuk berjalan sebagai pelayan mungkin menghilangkan persekitaran grafik dari pemasangan standard dan bukan termasuk perisian lain seperti Apache HTTP Server dan pelayan SSH seperti OpenSSH. 
8. Linux secara bebas disebarkan semula, adalah mungkin bagi siapa saja untuk membuat edaran untuk kegunaan yang dimaksudkan. Umumnya aplikasi yang digunakan oleh sistem Linux desktop termasuk Mozilla Firefox web browser, pejabat OpenOffice.org suite aplikasi dan editor gambar GIMP.

Command for LINUX

adduser

useradd [options] LOGIN

useradd -D

useradd -D [options]

DESCRIPTION

When invoked without the -D option, 

the useradd command creates a new user 

account using the values specified on 

the command line and the default 

values from the system. 

Depending on command line options, 

the useradd command will update system files 

and may also create the new user's 

home directory and copy initial files. 

The version provided with Red Hat Linux 

will create a group for each user 

added to the system by default.

OPTIONS

The options which apply to the useradd command are:

 -c, --comment COMMENT

  Any text string. It is generally a short description 

of the login,and is currently used as the field for 

the user's full name.

 -b, --base-dir BASE_DIR

  The default base directory for the system if  

-d dir is not specified.BASE_DIR is concatenated 

with the account name to define the home directory. 

If the -m option is not used, BASE_DIR must exist.

 -d, --home HOME_DIR

  The new user will be created using HOME_DIR as the 

value for the user's login directory. The default is 

to append the LOGIN name to BASE_DIR and use that as 

the login directory name. The directory HOME_DIR does 

not have to exist but will not be created if it is missing.

 -e, --expiredate EXPIRE_DATE

  The date on which the user account will be disabled. 

The date is specified in the format YYYY-MM-DD.

 -f, --inactive INACTIVE

  The number of days after a password expires until the 

account is permanently disabled. A value of 0 disables 

the account as soon as the password has expired,and a value 

of -1 disables the feature.The default value is -1.

-g, --gid GROUP

  The group name or number of the user's initial login group. 

The group name must exist. A group number must refer to an 

already existing group. 

 /etc/default/useradd.

 -G, --groups GROUP1[,GROUP2,...[,GROUPN]]]

  files contained in SKEL_DIR will be copied to the home 

directory if the -k option is used, otherwise the files 

contained in /etc/skel will be used instead.Any directories 

contained in SKEL_DIR or /etc/skel will be created in the 

user's home directory as well. The -k option is only valid 

in conjunction with the -m option. The default is to not 

create the directory and to not copy any files.

 -l Do not add the user to the last login log file. 

This is an option added by Red Hat.

 -n A group having the same name as the user being 

added to the system will be created by default. 

This option will turn off this Red Hat Linux 

specific behavior. When this option is used, 

users by default will be placed in 

whatever group is specified in /etc/default/useradd. 

If no default group is defined, group 1 will be used.

 -K, --key KEY=VALUE

  Overrides /etc/login.defs defaults(UID_MIN,UID_MAX,UMASK,

PASS_MAX_DAYS and others).

 Example: -K PASS_MAX_DAYS=-1 can be used when 

creating system account to turn off password ageing, 

even though system account has no password at all. 

Multiple -K options can be specified, 

e.g.: -K

    UID_MIN=100

    -K UID_MAX=499

Note: -K UID_MIN=10,UID_MAX=499 doesn't work yet.

 -o, --non-unique

  Allow the creation of a user account with a duplicate 

(non-unique)UID.

 -p, --password PASSWORD

  The encrypted password, as returned by crypt(3). 

The default is to disable the account.

 -r This flag is used to create a system account. 

That is, a user with a UID lower than the value of 

UID_MIN defined in /etc/login.defs and whose password 

does not expire. Note that useradd will not create a 

home directory for such an user, regardless of the 

default setting in /etc/login.defs. You have to specify  

-m option if you want a home directory for a system 

account to be created. This is an option added by Red Hat

 -s, --shell SHELL

  The name of the user's login shell. The default is to

leave this field blank, which causes the system to select 

the default login shell.

 -u, --uid UID

  The numerical value of the user's ID. This value must be unique.

 -b HOME_DIR

  The initial path prefix for a new user's home directory. 

The user's name will be affixed to the end of HOME_DIR to 

create the new directory name if the -d option is not used 

when creating a new account.

 -e EXPIRE_DATE

  The date on which the user account is disabled.

-f INACTIVE

  The number of days after a password has expired before the account 

will be disabled.

 -g, --gid GROUP

  The group name or ID for a new user's initial group. 

The named group must exist, and a numerical group ID must 

have an existing entry.

 -s, --shell SHELL

  The name of the new user's login shell. 

The named program will be used for all future new user accounts.

If no options are specified, useradd displays the current default

values.

NOTES

The system administrator is responsible for placing 

the default user files in the /etc/skel/ directory.

This version of useradd was modified by Red Hat to suit 

Red Hat user/group conventions.

CAVEATS

You may not add a user to a NIS group. 

This must be performed on the NIS server.Similarly,

if the username already exists in an external user database 

such as NIS, useradd will deny the user account creation request.

FILES

       /etc/passwd

          User account information.

       /etc/shadow

          Secure user account information.

       /etc/group

          Group account information.

       /etc/gshadow

          Secure group account information.

       /etc/default/useradd

       2  invalid command syntax

       3  invalid argument to option

       4  UID already in use (and no -o)

       6  specified group doesn't exist

       9  username already in use

       10 can't update group file

       12 can't create home directory

       13 can't create mail spool

ari nie kiter blj remote control yer.....

remote destop control ni kt guna utk kawal pc yg lain selain komputer kt sendiri..

how operation remote destop control

- memaparkan skrin komputer lain melalui internet dlm kawasan local pd paparan komputer sendiri.
- blh gunakan mouse dan keyboard utk control komputer lain dr jarak jauh.
- kt blh b'kerja pd komputer remote, seolah2 berada didepan komputer tersebut.
- cth:- xdpt pergi kerja krn sakit, kita blh siapkan kerja dirumah..asalkn remote destop control pd komputer pejabat 'ON'.

Just untuk pengetahuan jer....

TCP/IP

- Transmission Control Protokol/ Internet Protokol
- ia diguna dlm komunikasi sbg bahasa pengantaraan, tatacara
- terdapat 4 peringkat TCP/IP

•   Aplikasi
• Host to Host
• Network
• Link Interface 

- IP Address terbahagi kpd 2

• IPV4- 32 bit
• IPV6- 128 bit