Linux权限问题：“权限被拒绝”

Question

我正在TinyCore64机器上配置postgresql服务器，有一些文件和文件夹是postgres用户无法访问的，尽管我已经更改了所有内容的权限、所有权和组。以下是命令和文件夹结构：

sudo -u postgres ls /etc/ssl/
# success
# Permissions: drwxr-xr-x   6 root root

sudo -u postgres ls /etc/ssl/private
# ls: cannot open directory /etc/ssl/private/: Permission denied
# Permissions: drwxr-xr-x   2 postgres postgres

我被难住了。我做错了什么？

编辑：

贴出了确切的成绩单。

root@121e7b1cdaa4:~# sudo -u postgres ls -al /etc/ssl
total 28
drwxr-xr-x   6 root     root      4096 Jun 12 08:33 .
drwxr-xr-x 161 root     root      4096 Jun 12 08:33 ..
drwxr-xr-x   2 root     root      4096 Jun 12 08:33 certs
-rw-r--r--   1 root     root     10835 May  2 20:29 openssl.cnf
drwxr-xr-x   2 postgres postgres  4096 Jun 12 08:33 private
root@121e7b1cdaa4:~# sudo -u postgres ls -al /etc/ssl/private/
ls: cannot open directory /etc/ssl/private/: Permission denied

编辑：

发布了strace输出：

root@121e7b1cdaa4:~# strace -f sudo -u postgres ls -al /etc/ssl/private/
....
[pid  4270] close(3)                    = 0
[pid  4270] openat(AT_FDCWD, "/etc/ssl/private/", O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC) = -1 EACCES (Permission denied)
[pid  4270] write(2, "ls: ", 4ls: )         = 4
[pid  4270] write(2, "cannot open directory /etc/ssl/p"..., 39cannot open directory /etc/ssl/private/) = 39
[pid  4270] write(2, ": Permission denied", 19: Permission denied) = 19
[pid  4270] write(2, "\n", 1
)           = 1
....

Answer 1

检查"/etc/ssl“目录的权限-您系统上的'postgres‘用户似乎在目标系统的完整路径上没有'rx’权限。

它应该像这样：

kaa@aknb5:~$ ls -l /etc/ |grep ssl
drwxr-xr-x  4 root root     4096 Jun 13 11:00 ssl
kaa@aknb5:~$ uname -a
Linux aknb5 3.2.0-61-generic-pae #93-Ubuntu SMP Fri May 2 21:46:08 UTC 2014 i686 i686 i386 GNU/Linux
kaa@aknb5:~$