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==== linux grep per paragraph ====

[[linux:linux_grepp|Grep command per paragraph]]

==== Wrong TimeZone on OpenSuse ====

  cp /usr/share/zoneinfo/Europe/Riga /etc/localtime
  
==== Opensuse 12.3 ====

=== Loop back not working ===

Add:
  echo loop > /etc/modules-load.d/loop.conf
  
=== Crontab isn't working even if sevice seems working ===

  systemctl enable cron.service 
  
===== VNC blank screen =====

install the basic desktop on CentOS:
  yum groupinstall basic-desktop
  
===== Screen =====

Screen is deprecated into Redhat, now replaced by **TMUX**

https://www.redhat.com/sysadmin/introduction-tmux-linux

TMUX is a terminal using a background session, so you can run long process without being disconnected from TIMEOUT (TMOUT)
<cli prompt='$'>
$ tmux
</cli>

{{linux:tmux01.png?500}}

**For HELP**
  You can now run your first Tmux command. For example, to get a list of all commands, you would type:
  Ctrl+b ?

To start using tmux, type tmux on your terminal. This command launches a tmux server, creates a default session (number 0) with a single window, and attaches to it.

You can detach from your tmux session by pressing **Ctrl+B** then **D**. Tmux operates using a series of keybindings (keyboard shortcuts) triggered by pressing the "prefix" combination. By default, the prefix is Ctrl+B. After that, press D to detach from the current session.

List you background sessions
<cli prompt='$'>
$ tmux ls
0: 1 windows (created Sat Aug 27 20:54:58 2022)
</cli>

Connect to session number 0 (or maybe attach-session ?)
<cli prompt='$'>
$ tmux attach -t 0
</cli>
As you can see, the command continued to run and print messages on the screen. You can type Ctrl+C to cancel it.

Satart a session with specific name
  tmux new -s Session1

TMUX options
  * Ctrl+B D — Detach from the current session.
  * Ctrl+B % — Split the window into two panes horizontally.
  * Ctrl+B " — Split the window into two panes vertically.
  * Ctrl+B Arrow Key (Left, Right, Up, Down) — Move between panes.
  * Ctrl+B X — Close pane.
  * Ctrl+B C — Create a new window.
  * Ctrl+B N or P — Move to the next or previous window.
  * Ctrl+B 0 (1,2...) — Move to a specific window by number.
  * Ctrl+B : — Enter the command line to type commands. Tab completion is available.
  * Ctrl+B ? — View all keybindings. Press Q to exit.
  * Ctrl+B W — Open a panel to navigate across windows in multiple sessions.

then toggle the mouse on (or off) with the command set -g mouse.

Using colors:
  Change the status bar background color: set -g status-bg cyan
  Change inactive window color: set -g window-status-style bg=yellow
  Change active window color: set -g window-status-current-style bg=red,fg=white

=== Configure tmux ===

You can change the tmux configuration permanently by modifying the tmux configuration file. By default, this file is located at $HOME/.tmux.conf.

For example, the default prefix key combination is Ctrl+B, but sometimes this combination is a little awkward to press, and it requires both hands. You can change it to something different by editing the configuration file. I like to set the prefix key to Ctrl+A. To do this, create a new configuration file and add these lines to it:
<cli prompt='$'>
$ cat $HOME/.tmux.conf
# Set the prefix to Ctrl+a
set -g prefix C-a
# Remove the old prefix
unbind C-b
# Send Ctrl+a to applications by pressing it twice
bind C-a send-prefix
</cli>

Another example
<code>
# Improve colors
set -g default-terminal 'screen-256color'

# Set scrollback buffer to 10000
set -g history-limit 10000

# Customize the status line
set -g status-fg  green
set -g status-bg  black
</code>

=== Screen ===

//Only for historic info//

Screen (command) is a background terminal, you can start applications in background, quit your windows and recall your session.

Start a sceen session using a specific name
<cli prompt='#'>
# screen -S session_name
</cli>

Help
  Ctrl+a ?
  
Below are some most common commands for managing Linux Screen Windows:

  * Ctrl+a c Create a new window (with shell).
  * Ctrl+a " List all windows.
  * Ctrl+a 0 Switch to window 0 (by number).
  * Ctrl+a A Rename the current window.
  * Ctrl+a S Split current region horizontally into two regions.
  * Ctrl+a | Split current region vertically into two regions.
  * Ctrl+a tab Switch the input focus to the next region.
  * Ctrl+a Ctrl+a Toggle between the current and previous windows
  * Ctrl+a Q Close all regions but the current one.
  * Ctrl+a X Close the current region.

You can detach from the screen session at any time by typing:
  Ctrl+a d

Reattach to a Linux Screen:
  screen -r

To find the session ID list the current running screen sessions with:
<cli prompt='#'>
# screen -ls

There are screens on:
    10835.pts-0.linuxize-desktop   (Detached)
    10366.pts-0.linuxize-desktop   (Detached)
2 Sockets in /run/screens/S-linuxize.
</cli>

If you want to restore screen 10835.pts-0, then type the following command:
  screen -r 10835

===== limit a process =====

You can easily limit CPU usage with cpulimit command like:
<cli prompt='#'> 
# cpulimit -l 10 -- /usr/bin/clamscan -r / --exclude-dir=/sys/ --quiet --infected > /var/log/clamscan/clamscan.$(date +%Y%m%d).log
</cli>
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