=====Linux - Red Hat=====

=====Linux CentOS 6.5=====

  * To check what package to install: <code>yum whatprovides "*/scp"</code>
  * GB = 1,000 Megabytes
  * GiB  = 1,024 Megabytes
  * /var = install location
  * /home = user's home directories
  * / = root file system, 10 GiB
  * swap = temp files, 1 GiB
  * Install SNMP Utils<code>yum install -y net-snmp.x86_64 
yum install -y net-snmp-utils.x86_64</code>

====Enable SSH====
<code>chkconfig sshd on</code>

====Start SSH Service====
<code>service sshd restart</code>

====Add new user====
<code>useradd tst
passwd tst
password123
password123</code>

====Allow user root permissions====
<code>visudo</code>
  - Search for line that says ##Allow root to run any commands anywhere
  - Copy root line and change username

====Allow user sudo permissions====
  - For this, add a user to a group called wheel
<code>usermod -aG wheel tst</code>
  - Modify visudo to enable wheel group
<code>visudo</code>
   - Change line
<code>## Allows people in group wheel to run all commands
# %wheel  ALL=(ALL)  ALL</code>
   - Delete the comment in front to %wheel and the new line will look like
<code>%wheel  ALL=(ALL)  ALL</code>
=====Linux RHEL 6.5=====
  * Register with Red Hat Subscription Manager
<code>subscription-manager register
Username: 
Password: 
The system has been registered with ID: XXXXX</code>

=====Linux CentOS 7=====

  * 802.1X Authentication Tutorial
  * Index all files
<code>updatedb</code>
  * Change laptop lid closing behavior
<code>nano /etc/systemd/logind.conf</code>
    * Change **HandleLidSwitch** to:
      * **lock** to lock the screen
      * **ignore** to do nothing
      * **poweroff** to power off the pc
    * Preserve the settings upon reboot
<code>systemctl restart systemd-logind.service</code>
=====Red Hat Linux 7.3=====
  * GB = 1,000 Megabytes
  * GiB  = 1,024 Megabytes
  * /var = install location
  * /home = user's home directories
  * / = root file system, 10 GiB
  * swap = temp files, 1 GiB
  * <CTRL> + <l> (L) to wipe screen
  * mandb
    * man -k user
      * (List man pages with text 'user')
    * man -k user | wc (word count)
      * lines, words, characters
    * man -k user | grep 8
    * man -k user | grep 8 | grep create
  * Start vim->Command Mode->Insert mode
    * press 'a', 'i', 'o', or <INS> to go from Command Mode to Insert Mode
    * rest of commands are like vi
    * modes:
      * i = insert
      * o = open new line
      * a = add
      * <ESC> = go back to Command Mode
      * :wq = write, quit
      * ZZ = write, quit
    * Editing
      * dd = remove a line (cut)
      * yy = copy a link (copy)
      * dd and yy are written to a buffer
      * p = paste from buffer (paste)
    * Managing
      * u = undo
      * <CTRL> + <r> = redo
      * v + arrow keys = select characters
      * :q! = quit without saving
    * Useful
      * :%s/old/new/g = look for text 'old' and replace with 'new'
        * %s = substitue
        * g = replace with
      * G = goto end of document

=====Linux CentOS 8=====

[[https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/installation_guide/data-size-appendix|DATA SIZE TERMINOLOGY REFERENCE TABLE]]


====Backlinks====
[[:linux|Linux]]