Update cheatsheets

tldr/gdm

@@ -0,0 +1,34 @@
+---
+syntax: markdown
+tags: [tldr, common]
+source: https://github.com/tldr-pages/tldr.git
+---
+# gdm
+
+> The GNOME Display Manager (GDM) is a replacement for the X Display Manager (XDM).
+> See also: `gdm-binary`, `gdmsetup`, `gdm-stop`, `gdm-restart`, `gdm-safe-restart`.
+> More information: <https://manned.org/gdm>.
+
+- Run the GNOME Display Manager application:
+
+`gdm`
+
+- Prevent `gdm` from being run as a daemon background process:
+
+`gdm --nodaemon`
+
+- Disable `gdm` management of local console X servers for headless or remote environments:
+
+`gdm --no-console`
+
+- Prevent sanitizing environment variables that start with `LD_`:
+
+`gdm --preserve-ld-vars`
+
+- Display help:
+
+`gdm --help`
+
+- Display version:
+
+`gdm --version`

tldr/grep

@@ -26,7 +26,7 @@ source: https://github.com/tldr-pages/tldr.git
 
 - Print 3 lines of [C]ontext around, [B]efore or [A]fter each match:
 
-`grep --{{context|before-context|after-context}} 3 "{{search_pattern}}" {{path/to/file}}`
+`grep {{--context|--before-context|--after-context}} 3 "{{search_pattern}}" {{path/to/file}}`
 
 - Print file name and line number for each match with color output:
 

tldr/nagios

@@ -0,0 +1,27 @@
+---
+syntax: markdown
+tags: [tldr, common]
+source: https://github.com/tldr-pages/tldr.git
+---
+# nagios
+
+> Legacy host/service/networking monitoring program.
+> Largely deprecated by `nagios4`.
+> See also: `nagios2`, `nagios3`, `nagios4`.
+> More information: <https://manned.org/nagios>.
+
+- Start `nagios`:
+
+`nagios /etc/nagios/nagios.cfg`
+
+- Start `nagios` in daemon mode:
+
+`nagios -d`
+
+- Start `nagios`, print service check scheduling information to `stdout`, then shutdown:
+
+`nagios -s`
+
+- Verify configuration file:
+
+`nagios -v`

tldr/nagios2

@@ -0,0 +1,27 @@
+---
+syntax: markdown
+tags: [tldr, common]
+source: https://github.com/tldr-pages/tldr.git
+---
+# nagios2
+
+> Legacy host/service/networking monitoring program.
+> Largely deprecated by `nagios4`.
+> See also: `nagios`, `nagios3`, `nagios4`.
+> More information: <https://manned.org/nagios>.
+
+- Start `nagios2`:
+
+`nagios2 /etc/nagios2/nagios.cfg`
+
+- Start `nagios2` in daemon mode:
+
+`nagios2 -d`
+
+- Start `nagios2`, print service check scheduling information to `stdout`, then shutdown:
+
+`nagios2 -s`
+
+- Verify configuration file:
+
+`nagios2 -v`

tldr/nagios3

@@ -0,0 +1,27 @@
+---
+syntax: markdown
+tags: [tldr, common]
+source: https://github.com/tldr-pages/tldr.git
+---
+# nagios3
+
+> Legacy host/service/networking monitoring program.
+> Largely deprecated by `nagios4`.
+> See also: `nagios`, `nagios2`, `nagios4`.
+> More information: <https://manned.org/nagios>.
+
+- Start `nagios3`:
+
+`nagios3 /etc/nagios3/nagios.cfg`
+
+- Start `nagios3` in daemon mode:
+
+`nagios3 -d`
+
+- Start `nagios3`, print service check scheduling information to `stdout`, then shutdown:
+
+`nagios3 -s`
+
+- Verify configuration file:
+
+`nagios3 -v`

tldr/nagios4

@@ -0,0 +1,26 @@
+---
+syntax: markdown
+tags: [tldr, common]
+source: https://github.com/tldr-pages/tldr.git
+---
+# nagios4
+
+> Legacy host/service/networking monitoring program.
+> See also: `nagios`, `nagios2`, `nagios3`.
+> More information: <https://manned.org/nagios>.
+
+- Start `nagios4`:
+
+`nagios4 /etc/nagios4/nagios.cfg`
+
+- Start `nagios4` in daemon mode:
+
+`nagios4 -d`
+
+- Start `nagios4`, print service check scheduling information to `stdout`, then shutdown:
+
+`nagios4 -s`
+
+- Verify configuration file:
+
+`nagios4 -v`

tldr/pgcli

@@ -0,0 +1,21 @@
+---
+syntax: markdown
+tags: [tldr, common]
+source: https://github.com/tldr-pages/tldr.git
+---
+# pgcli
+
+> A modern PostgreSQL CLI with auto-completion and syntax highlighting.
+> More information: <https://www.pgcli.com>.
+
+- Connect to a PostgreSQL database using a connection string:
+
+`pgcli postgresql://{{user}}@{{host}}/{{database}}`
+
+- Connect to a database using flags:
+
+`pgcli {{[-h|--host]}} {{host}} {{[-U|--username]}} {{username}} {{[-d|--dbname]}} {{database}}`
+
+- Display help:
+
+`pgcli --help`