use ssh key file

code/backup_rsync_git.env.example

@@ -8,5 +8,11 @@ RSYNC_TARGET_DIR="/path/to/backup-repo"
 # Prefix for commit message (timestamp is appended automatically)
 COMMIT_MESSAGE_PREFIX="backup: rsync sync"
 
-# Optional: custom SSH command for rsync (leave empty if not needed)
+# SSH key file used by rsync/ssh
+SSH_KEY_FILE="/root/.ssh/backup_rsync"
+
+# Optional extra SSH options
+# SSH_OPTIONS="-o IdentitiesOnly=yes -o StrictHostKeyChecking=yes"
+
+# Optional full custom SSH command for rsync (overrides SSH_KEY_FILE/SSH_OPTIONS)
 # RSYNC_RSH="ssh -i /path/to/key -o StrictHostKeyChecking=yes"