wiki

Grep command per paragraph

cp /usr/share/zoneinfo/Europe/Riga /etc/localtime

Add:

echo loop > /etc/modules-load.d/loop.conf

systemctl enable cron.service 

install the basic desktop on CentOS:

yum groupinstall basic-desktop

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)

$ tmux

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

$ tmux ls
0: 1 windows (created Sat Aug 27 20:54:58 2022)

Connect to session number 0 (or maybe attach-session ?)

$ tmux attach -t 0

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

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:

$ 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

Another example

# 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

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

# screen -S session_name

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:

# 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.

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

screen -r 10835

You can easily limit CPU usage with cpulimit command like:

# cpulimit -l 10 -- /usr/bin/clamscan -r / --exclude-dir=/sys/ --quiet --infected > /var/log/clamscan/clamscan.$(date +%Y%m%d).log