以下のような状況を想定．
% ls -Rla
.:
total 0
drwxr-xr-x 1 myn users 24 Jul 12 12:06 ./
drwxr-xr-x 1 myn users 2018 Jul 12 12:12 ../
drwxr-xr-x 1 myn users 8 Jul 12 12:13 low/
drwxr-xr-x 1 myn users 0 Jul 12 12:06 over/
drwxr-xr-x 1 myn users 16 Jul 12 12:14 up/
drwxr-xr-x 1 myn users 0 Jul 12 12:14 work/
./low:
total 0
drwxr-xr-x 1 myn users 8 Jul 12 12:13 ./
drwxr-xr-x 1 myn users 24 Jul 12 12:06 ../
drwxr-xr-x 1 myn users 18 Jul 12 12:08 dir0/
./low/dir0:
total 0
drwxr-xr-x 1 myn users 18 Jul 12 12:08 ./
drwxr-xr-x 1 myn users 8 Jul 12 12:13 ../
-rw-r--r-- 1 myn users 0 Jul 12 12:05 test
-rw-r--r-- 1 myn users 0 Jul 12 12:05 test1
./over:
total 0
drwxr-xr-x 1 myn users 0 Jul 12 12:06 ./
drwxr-xr-x 1 myn users 24 Jul 12 12:06 ../
./up:
total 0
drwxr-xr-x 1 myn users 16 Jul 12 12:14 ./
drwxr-xr-x 1 myn users 24 Jul 12 12:06 ../
c--------- 1 root root 0, 0 Jul 6 11:18 dir0
drwxr-xr-x 1 myn users 20 Jul 12 12:14 dir1/
./up/dir1:
total 0
drwxr-xr-x 1 myn users 20 Jul 12 12:14 ./
drwxr-xr-x 1 myn users 16 Jul 12 12:14 ../
-rw-r--r-- 1 myn users 0 Jul 12 12:09 file0
c--------- 1 root root 0, 0 Jul 6 11:18 file1
./work:
total 0
drwxr-xr-x 1 myn users 0 Jul 12 12:14 ./
drwxr-xr-x 1 myn users 24 Jul 12 12:06 ../ここで
% sudo mount -t overlay -olowerdir=low,upperdir=up,workdir=work overlay overで mount すると，
% ls -Rla over
over:
total 0
drwxr-xr-x 1 myn users 16 Jul 12 12:14 ./
drwxr-xr-x 1 myn users 26 Jul 12 12:16 ../
drwxr-xr-x 1 myn users 20 Jul 12 12:14 dir1/
over/dir1:
ls: cannot access 'over/dir1/file1': No such file or directory
total 0
drwxr-xr-x 1 myn users 20 Jul 12 12:14 ./
drwxr-xr-x 1 myn users 16 Jul 12 12:14 ../
-rw-r--r-- 1 myn users 0 Jul 12 12:09 file0
c????????? ? ? ? ? ? file1といった悲しい状況になる．upper 側で消すファイルが lower 側に存在せず，かつ，その directory が upper 側でのみ存在する場合に発生する様子(しかも起こったり起こらなかったり)．Linux の Version は 4.17.5．