Add question about tracking system level files (#63)

_docs/110_faq.md

@@ -159,6 +159,31 @@ https://github.com/TheLocehiliosan/yadm/commits/git-crypt-support
 https://github.com/TheLocehiliosan/yadm/commit/efb7fd16612fe650b1286f0c696696f412772ab3
 ) in the commit messages of that branch for details.
 
+## Unconventional Cases
+
+### Can I use yadm to track system level files?
+
+yadm only manages files within the configured worktree (`$HOME` by default).
+Also, yadm will use the effective user for file ownership just like Git.
+However, if you want to bend yadm into managing system files, one method is:
+
+```
+# create an alias to run yadm for system files
+alias sysyadm="sudo yadm -Y /etc/yadm"
+
+# initialize the yadm repo using the worktree of "/"
+sysyadm init -w /
+
+# continue to use sysyadm for managing system files
+sysyadm add /etc/something.conf
+sysyadm commit -m 'Add something.conf'
+```
+
+Assuming you have "sudo" rights, the `sysyadm` alias will work as if root was using
+yadm, having the owner be "root", with the ability to manage any file under `/`.
+If you were only interested in managing files under `/etc`, you could use that as
+the worktree instead.
+
 ## Comparisons
 
 ### How does yadm differ from homeshick?