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为什么“rm -r”无法删除该文件夹？

tag-icon • tag-icon linux permissions rm
为什么“rm -r”无法删除该文件夹？

我有一个-wx名为“权限”的文件夹folder1，其中的另一个文件夹名为folder2“rwx权限”。

我尝试folder1使用以下命令删除：

rm -r folder1

但我收到以下错误：

rm: cannot remove 'folder1': Permission denied

我认为我收到此错误的原因是因为程序rm需要首先获取内容folder1（获取其中的文件和文件夹的名称folder1）以便能够删除该内容（因为您无法删除文件或文件夹，我认为不知道其名称），然后rm程序可以folder1自行删除。

但由于folder1没有权限read，那么rm程序无法获取其内容，因此无法删除其内容，并且由于无法删除其内容，因此也无法删除它。

我对么？

答案1

我认为你的分析是正确的：你不能删除该目录，因为它非空，并且你不能清空它，因为你看不到它的内容。

我刚刚尝试了一下：

$ mkdir -p folder1/folder2
$ chmod -r folder1
$ rm -rf folder1
rm: cannot remove 'folder1': Permission denied
$ rmdir folder1/folder2
$ rm -rf folder1
$

当我写“你”时，我指的是你可以运行的任何程序。您的rm -r命令首先看到这folder1是一个目录，因此它尝试发现其内容以清空它，但由于缺少读取权限而失败，然后它尝试删除它但失败，因为它不为空。 “许可被拒绝”具有误导性；我认为“目录不为空”（如rmdir报告）会更合适。）

答案2

为了进行删除，系统必须能够读取内容并识别必须删除的内容。

我尝试模拟你正在尝试的事情：

[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 ~]$

如果我们尝试在没有读取权限的情况下删除，则会失败：

[vagrant@desktop1 ~]$ rm -r folder1/
rm: cannot remove 'folder1/': Permission denied
[vagrant@desktop1 ~]$ sudo chmod +r folder1/
[vagrant@desktop1 ~]$ rm -r folder1/
[vagrant@desktop1 ~]$

在两次尝试的 strace 中，区别在于无法读取目录内容（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

具有读取权限：

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

总而言之，即使您拥有一个目录并且它具有可执行位，您仍然需要读取权限，以便您可以查看其内容并删除该文件夹。但对于文件来说并不相同。

答案3

好吧，我没有足够的声誉来评论 ttaran7 的答案，所以它看起来像是一个必须的答案。由于声誉较低，我的赞成票也不公开可见。我对这个答案投了赞成票，因为它实际上包含了系统调用跟踪，而不仅仅是猜测。

回答OP的问题：是的，你的推理是正确的：你因无法读取目录而被阻止

我对他们（ttaran7）所做的进行了类似的跟踪，因为我怀疑同样的推理：rm由于无法读取目录，调用将失败，这将是结束，没有机会抱怨目录为空。在再次查看我所获取的跟踪后，我注意到进行了系统调用以尝试取消链接所提供的文件名：

newfstatat(AT_FDCWD, "folder1", {st_mode=S_IFDIR|0311, st_size=4096, ...}, AT_SYMLINK_NOFOLLOW) = 0
openat(AT_FDCWD, "folder1", O_RDONLY|O_NOCTTY|O_NONBLOCK|O_NOFOLLOW|O_DIRECTORY) = -1 EACCES (Permission denied)
openat(AT_FDCWD, "folder1", O_RDONLY|O_NOCTTY|O_NONBLOCK|O_NOFOLLOW|O_CLOEXEC|O_DIRECTORY) = -1 EACCES (Permission denied)
unlinkat(AT_FDCWD, "folder1", AT_REMOVEDIR) = -1 ENOTEMPTY (Directory not empty)
openat(AT_FDCWD, "/usr/share/locale/locale.alias", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=2995, ...}) = 0
read(3, "# Locale name alias data base.\n#"..., 4096) = 2995
read(3, "", 4096)                       = 0
close(3)                                = 0
openat(AT_FDCWD, "/usr/share/locale/en_AU/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/usr/share/locale/en/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/usr/share/locale-langpack/en_AU/LC_MESSAGES/coreutils.mo", O_RDONLY) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=45256, ...}) = 0
mmap(NULL, 45256, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7f8db25ca000
close(3)                                = 0
openat(AT_FDCWD, "/usr/share/locale- langpack/en/LC_MESSAGES/coreutils.mo", O_RDONLY) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=578, ...}) = 0
mmap(NULL, 578, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7f8db25c9000
close(3)                                = 0
write(2, "rm: ", 4rm: )                     = 4
write(2, "cannot remove 'folder1'", 23cannot remove 'folder1') = 23
openat(AT_FDCWD, "/usr/share/locale/en_AU/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/usr/share/locale/en/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/usr/share/locale-langpack/en_AU/LC_MESSAGES/libc.mo", O_RDONLY) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=2893, ...}) = 0
mmap(NULL, 2893, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7f8db25c8000
close(3)                                = 0
openat(AT_FDCWD, "/usr/share/locale-langpack/en/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
write(2, ": Permission denied", 19: Permission denied)     = 19
write(2, "\n", 1
lseek(0, 0, SEEK_CUR)                   = -1 ESPIPE (Illegal seek)
close(0)                                = 0
close(1)                                = 0
close(2)                                = 0
exitgroup(1)

看第四行：unlinkat... 失败，因为目录不为空。现在这就是我认为的意外行为，事实上它尝试完全删除该目录，尽管没有读取权限。

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