Ygthkb

I have a folder with -wx permissions called folder1 and another folder inside it called folder2 with rwx permissions.

I tried to delete folder1 using this command:

rm -r folder1

But I got the following error:

rm: cannot remove 'folder1': Permission denied

The reason I think I got this error is because the rm program needs to first get the content of folder1 (get the names of the files and folders inside folder1 that is) in order to be able to delete that content (because you can't delete a file or folder without knowing its name I think), and then the rm program can delete folder1 itself.

But since folder1 doesn't have the read permission, then the rm program can't get its content, and hence it can't delete its content, and since it can't delete its content, then it can't delete it.

Am I correct?

I think your analysis is correct: you cannot delete the directory since its non-empty, and you cannot empty it since you cannot see its contents.

EDIT: I just gave it a try:

$ mkdir -p folder1/folder2

$ chmod -r folder1

$ rm -rf folder1

rm: cannot remove 'folder1': Permission denied

$ rmdir folder1/folder2

$ rm -rf folder1

$ 

EDIT 2: When I wrote “you”, I meant any program you may run. Your rm -r command first sees that folder1 is a directory, so it tries to discover its contents to empty it, but fails for missing read permission, then it tries to delete it but fails because it’s non-empty. The “Permission denied” is misleading; I think “Directory not empty” (like rmdir reports) would be more appropriate.)

For deletion to occur the system must be able to read the contents and identify what has to be deleted.

I've tried simulating what you are attempting :

[vagrant@desktop1 ~]$ sudo rm -rf folder1/ && mkdir -pv folder1/folder2 && sudo chmod 333 -v folder1/ && sudo chmod 777 -v folder1/folder2

mkdir: created directory 'folder1'

mkdir: created directory 'folder1/folder2'

mode of 'folder1/' changed from 0775 (rwxrwxr-x) to 0333 (-wx-wx-wx)

mode of 'folder1/folder2' changed from 0775 (rwxrwxr-x) to 0777 (rwxrwxrwx)

[vagrant@desktop1 ~]$ ls -lh

total 0

d-wx-wx-wx. 3 vagrant vagrant 21 Feb 24 10:40 folder1

[vagrant@desktop1 ~]$ 

If we try deleting without read permissions it fails:

[vagrant@desktop1 ~]$ rm -r folder1/

rm: cannot remove 'folder1/': Permission denied

[vagrant@desktop1 ~]$ sudo chmod +r folder1/

[vagrant@desktop1 ~]$ rm -r folder1/

[vagrant@desktop1 ~]$ 

In an strace for the two attempts the difference is that the directory contents cannot be read (getdents):

newfstatat(AT_FDCWD, "folder1/", {st_mode=S_IFDIR|0333, st_size=21, ...}, AT_SYMLINK_NOFOLLOW) = 0

openat(AT_FDCWD, "folder1/", O_RDONLY|O_NOCTTY|O_NONBLOCK|O_DIRECTORY|O_NOFOLLOW) = -1 EACCES (Permission denied)

geteuid()                               = 1000

newfstatat(AT_FDCWD, "folder1/", {st_mode=S_IFDIR|0333, st_size=21, ...}, AT_SYMLINK_NOFOLLOW) = 0

faccessat(AT_FDCWD, "folder1/", W_OK)   = 0

openat(AT_FDCWD, "folder1/", O_RDONLY|O_NOCTTY|O_NONBLOCK|O_DIRECTORY|O_NOFOLLOW) = -1 EACCES (Permission denied)

newfstatat(AT_FDCWD, "folder1/", {st_mode=S_IFDIR|0333, st_size=21, ...}, AT_SYMLINK_NOFOLLOW) = 0

With read permissions:

newfstatat(AT_FDCWD, "folder1/", {st_mode=S_IFDIR|0777, st_size=21, ...}, AT_SYMLINK_NOFOLLOW) = 0

openat(AT_FDCWD, "folder1/", O_RDONLY|O_NOCTTY|O_NONBLOCK|O_DIRECTORY|O_NOFOLLOW) = 3

fstat(3, {st_mode=S_IFDIR|0777, st_size=21, ...}) = 0

fcntl(3, F_GETFL)                       = 0x38800 (flags O_RDONLY|O_NONBLOCK|O_LARGEFILE|O_DIRECTORY|O_NOFOLLOW)

fcntl(3, F_SETFD, FD_CLOEXEC)           = 0

getdents(3, /* 3 entries */, 32768)     = 80

close(3)                                = 0

geteuid()                               = 1000

To conclude even if you own a directory and it has the executable bit, you still need read permissions so that you may see its contents and delete the folder. It's not the same for a file though.

Kind regards,

Taran.