Update cheatsheets

linux/hwclock

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+---
+syntax: markdown
+tags: [tldr, linux]
+source: https://github.com/tldr-pages/tldr.git
+---
+# hwclock
+
+> Read or change the hardware clock. Usually requires root.
+> More information: <https://manned.org/hwclock>.
+
+- Display the current time as reported by the hardware clock:
+
+`hwclock`
+
+- Write the current software clock time to the hardware clock (sometimes used during system setup):
+
+`hwclock --systohc`
+
+- Write the current hardware clock time to the software clock:
+
+`hwclock --hctosys`