fwupdtool: add page, fwupdmgr: refer to fwupdtool and add example (#16577)

Co-authored-by: Sebastiaan Speck <12570668+sebastiaanspeck@users.noreply.github.com>

pages/linux/fwupdmgr.md

@@ -1,9 +1,10 @@
 # fwupdmgr
 
 > Update device firmware, including UEFI, using `fwupd`.
-> More information: <https://fwupd.org/>.
+> See also: `fwupdtool`.
+> More information: <https://github.com/fwupd/fwupd/blob/main/src/fwupdmgr.md>.
 
-- Display all devices detected by fwupd:
+- Display all devices detected by `fwupd`:
 
 `fwupdmgr get-devices`
 
@@ -18,3 +19,7 @@
 - Install firmware updates:
 
 `fwupdmgr update`
+
+- Remount `/boot` with more privileges if update complains about a read-only filesystem:
+
+`sudo mount {{[-o|--options]}} uid=1000,gid=1000,umask=0022 {{/dev/sdX}} /boot`

pages/linux/fwupdtool.md

@@ -0,0 +1,17 @@
+# fwupdtool
+
+> Update device firmware manually or manipulate firmware files.
+> See also: `fwupdmgr`.
+> More information: <https://github.com/fwupd/fwupd/blob/main/src/fwupdtool.md>.
+
+- Display all devices detected by `fwupd`:
+
+`fwupdtool get-devices`
+
+- Install firmware from a file:
+
+`fwupdtool install {{path/to/firmware}}`
+
+- Display help:
+
+`fwupdtool {{[-h|--help]}}`