update-initramfs: add page (#17552)

Co-authored-by: Fazle Arefin <fazlearefin@users.noreply.github.com>

pages/linux/update-initramfs.md

@@ -0,0 +1,16 @@
+# update-initramfs
+
+> Manage initramfs.
+> More information: <https://manned.org/update-initramfs>.
+
+- Create a new initramfs (use `all` for all installed kernel versions):
+
+`sudo update-initramfs -c -k {{kernel_version}}`
+
+- Update an existing initramfs:
+
+`sudo update-initramfs -u`
+
+- Remove an existing initramfs (be careful when using `all` for `kernel_version`):
+
+`sudo update-initramfs -d -k {{kernel_version}}`