$ du -a /opt|sort -n ... 19120408 /opt/app/oracle/admin/orcl/work/dump/exp_orcl_20100203123851.dmp 19120536 /opt/app/oracle/admin/orcl/work/dump/exp_orcl_20100203150412.dmp 19789772 /opt/app/oracle/oradata/orcl/temp07.dbf 19811300 /opt/app/oracle/oradata/orcl/temp06.dbf 19848200 /opt/app/oracle/oradata/orcl/temp05.dbf 19910724 /opt/app/oracle/oradata/orcl/temp04.dbf 19995800 /opt/app/oracle/oradata/orcl/temp03.dbf 49660280 /opt/app/oracle/admin/orcl/work/dump 160065180 /opt/app/oracle/admin/orcl/work/imp_schema/scott_201002_TEMP.dmp 160066044 /opt/app/oracle/admin/orcl/work/imp_schema 223956496 /opt/app/oracle/admin/orcl/work 232741724 /opt/app/oracle/admin/orcl 232741728 /opt/app/oracle/admin 1691683176 /opt/app/oracle/oradata/orcl 1691683180 /opt/app/oracle/oradata 1925968816 /opt/app/oracle 1925968820 /opt/app 1925969804 /opt
関連
追記(2016/02/21):
容量をくってるベスト100を表示
du -ma | sort -rn | head -100ディレクトリのみを検索する場合はこちら
du -m | sort -rn | head -100linux ファイル容量降順にソート - Qiita