Update cheatsheets

tldr/linux/nft-monitor

@@ -0,0 +1,25 @@
+---
+syntax: markdown
+tags: [tldr, linux]
+source: https://github.com/tldr-pages/tldr.git
+---
+# nft monitor
+
+> Show real-time changes happening inside the Linux firewall `nftables`.
+> More information: <https://manned.org/nft#head21>.
+
+- Monitor all nftables events:
+
+`sudo nft monitor`
+
+- Monitor only rule updates (add, delete, replace):
+
+`sudo nft monitor rules`
+
+- Monitor set and element updates:
+
+`sudo nft monitor sets`
+
+- Monitor events and print JSON output:
+
+`sudo nft {{[-j|--json]}} monitor`

tldr/linux/systemctl-kexec

@@ -0,0 +1,17 @@
+---
+syntax: markdown
+tags: [tldr, linux]
+source: https://github.com/tldr-pages/tldr.git
+---
+# systemctl kexec
+
+> Reboot the system via kexec.
+> More information: <https://www.freedesktop.org/software/systemd/man/systemctl.html#kexec>.
+
+- Fast reboot using kexec (if kernel is pre-loaded):
+
+`systemctl kexec`
+
+- Force normal reboot even if kexec is available:
+
+`systemctl kexec {{[-f|--force]}}`