Update cheatsheets

tldr/linux/dd

@@ -27,7 +27,7 @@ source: https://github.com/tldr-pages/tldr.git
 
 - Create a system backup, save it into an IMG file (can be restored later by swapping `if` and `of`), and show the progress:
 
-`dd if={{/dev/drive_device}} of={{path/to/file.img}} status=progress`
+`sudo dd if={{/dev/drive_device}} of={{path/to/file.img}} status=progress`
 
 - Check the progress of an ongoing `dd` operation (run this command from another shell):
 

tldr/linux/envycontrol

@@ -12,9 +12,9 @@ source: https://github.com/tldr-pages/tldr.git
 
 `sudo envycontrol {{[-s|--switch]}} {{nvidia|integrated|hybrid}}`
 
-- Specify your display manager manually:
+- Specify your [d]isplay [m]anager manually:
 
-`envycontrol --dm`
+`envycontrol --dm {{gdm|gdm3|sddm|lightdm}}`
 
 - Check current GPU mode:
 

tldr/linux/head

@@ -6,6 +6,7 @@ source: https://github.com/tldr-pages/tldr.git
 # head
 
 > Output the first part of files.
+> See also: `tail`.
 > More information: <https://www.gnu.org/software/coreutils/manual/html_node/head-invocation.html>.
 
 - Show first 10 lines in a file:

tldr/linux/natural-selection-2

@@ -0,0 +1,37 @@
+---
+syntax: markdown
+tags: [tldr, linux]
+source: https://github.com/tldr-pages/tldr.git
+---
+# Natural Selection 2
+
+> Start a headless Natural Selection 2 server.
+> More information: <https://naturalselection.fandom.com/wiki/Dedicated_Server>.
+
+- Start a server with the default settings:
+
+`{{path/to/server_linux}}`
+
+- Give a server a custom name that shows in the server browser:
+
+`{{path/to/server_linux}} -name '{{server_name}}'`
+
+- Specify a connection port for the server:
+
+`{{path/to/server_linux}} -port {{27015}}`
+
+- Specify maximum player count:
+
+`{{path/to/server_linux}} -limit {{2..24}}`
+
+- Specify the initial map the server starts on:
+
+`{{path/to/server_linux}} -map {{ns2_summit}}`
+
+- Limit access to the server with a password:
+
+`{{path/to/server_linux}} -password {{password}}`
+
+- Start a server with webui admin interface:
+
+`{{path/to/server_linux}} -webadmin -webport {{8080}}`

tldr/linux/sleep

@@ -23,3 +23,11 @@ source: https://github.com/tldr-pages/tldr.git
 - Execute a specific command after 20 [m]inutes delay:
 
 `sleep 20m && {{command}}`
+
+- Delay forever:
+
+`sleep {{[inf|infinity]}}`
+
+- Display help:
+
+`sleep --help`