create/update 'blog - fun with find.md' file

blog - fun with find.md

@@ -45,3 +45,18 @@ find /var/log/hbase -type f -iname "*log*" -mtime +360 -delete
 Replace `hbase` with the log directory you want to search.  If you don't need to save the archives anywhere, skip step two.
 
 [Reference](https://www.cyberciti.biz/faq/linux-unix-find-tar-files-into-tarball-command/)
+
+---
+
+## Find files by group and mode
+
+Note: *from Teachingbooks web directory permission fix.* at OverDrive
+
+Find files that have `group: www-data` and current `permissions: 644`, then update the permissions to 664
+
+```bash
+find <directory> -type f -group www-data -perm 644 -exec ls -al {} \;
+find <directory> -type f -group www-data -perm 644 -exec chmod g+w {} \;
+```
+
+[Reference](https://ostechnix.com/find-files-based-permissions/)