====== Linux Commands ======

===== tmux =====


<code>
tmux new -s build
tmux detach            # or Ctrl+b d
tmux ls
tmux attach -t 0
tmux kill-session -t 0
tmux switch -t 0
tmux rename-session -t 0 <new_name>
</code>

To create a new tab, ''Ctrl+b c''.

Switch between tabs, ''Ctrl+b <tab_number>''.

===== Copy =====

copy "new" folder to the "old" folder, and cover all files in "old".

  cp -frap new/* old/

  * ''-f'' is force
  *  ''-r'' means recursive, include any folder
  * ''-a'' make a backup. Don't rely on it!
  * ''-p'' Keep the properties of this file.

===== Systemd =====

A sample service file:

<code - gitea.service>
[Unit]
Description=Gitea (Git with a cup of tea)
After=syslog.target
After=network.target
#After=mysqld.service
#After=postgresql.service
#After=memcached.service
#After=redis.service

[Service]
#LimitMEMLOCK=infinity
#LimitNOFILE=65535
RestartSec=2s
Type=simple
User=git
Group=git
WorkingDirectory=/home/git
ExecStart=/usr/local/bin/gitea web -c /etc/gitea/app.ini
Restart=always
#Environment=USER=git HOME=/home/git GITEA_WORK_DIR=/home/git

[Install]
WantedBy=multi-user.target
</code>

So, the right way to implement ''Environment'' is to run ''systemctl edit myservice''.

In normal installations this will create a directory ''/etc/systemd/system/myservice.service.d'', and inside that directory create a file whose name ends in ''.conf'' (typically, ''override.conf''), and in this file you can add to or override any part of the unit shipped by the distribution.

For instance, in a file /etc/systemd/system/myservice.service.d/myenv.conf:

<code>
[Service]
Environment="USER=git"
Environment="HOME=/home/git"
Environment="GITEA_WORK_DIR=/home/git"
</code>

Also note that if the directory exists and is empty, your service will be disabled! If you don't intend to put something in the directory, ensure that it does not exist.

[[https://serverfault.com/questions/413397/how-to-set-environment-variable-in-systemd-service|Copied from here]].