Update cheatsheets

tldr/linux/firejail

@@ -31,3 +31,11 @@ source: https://github.com/tldr-pages/tldr.git
 - Shutdown a running sandbox:
 
 `firejail --shutdown={{7777}}`
+
+- Run a restricted Firefox session to browse the internet:
+
+`firejail --seccomp --private --private-dev --private-tmp --protocol=inet firefox --new-instance --no-remote --safe-mode --private-window`
+
+- Use custom hosts file (overriding `/etc/hosts` file):
+
+`firejail --hosts-file={{~/myhosts}} {{curl http://mysite.arpa}}`

tldr/linux/showkey

@@ -0,0 +1,29 @@
+---
+syntax: markdown
+tags: [tldr, linux]
+source: https://github.com/tldr-pages/tldr.git
+---
+# showkey
+
+> Display the keycode of pressed keys on the keyboard, helpful for debugging keyboard-related issues and key remapping.
+> More information: <https://manned.org/showkey>.
+
+- View keycodes in decimal:
+
+`sudo showkey`
+
+- Display [s]cancodes in hexadecimal:
+
+`sudo showkey {{-s|--scancodes}}`
+
+- Display [k]eycodes in decimal (default):
+
+`sudo showkey {{-k|--keycodes}}`
+
+- Display keycodes in [a]SCII, decimal, and hexadecimal:
+
+`sudo showkey {{-a|--ascii}}`
+
+- Exit the program:
+
+`Ctrl + d`

tldr/linux/tunelp

@@ -0,0 +1,30 @@
+---
+syntax: markdown
+tags: [tldr, linux]
+source: https://github.com/tldr-pages/tldr.git
+---
+# tunelp
+
+> Set various parameters for parallel port devices for troubleshooting or for better performance.
+> Part of `util-linux`.
+> More information: <https://manned.org/tunelp>.
+
+- Check the [s]tatus of a parallel port device:
+
+`tunelp --status {{/dev/lp0}}`
+
+- [r]eset a given parallel port:
+
+`tunelp --reset {{/dev/lp0}}`
+
+- Use a given [i]RQ for a device, each one representing an interrupt line:
+
+`tunelp -i 5 {{/dev/lp0}}`
+
+- Try a given number of times to output a [c]haracter to the printer before sleeping for a given [t]ime:
+
+`tunelp --chars {{times}} --time {{time_in_centiseconds}} {{/dev/lp0}}`
+
+- Enable or disable [a]borting on error (disabled by default):
+
+`tunelp --abort {{on|off}}`