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如何知道为什么我有读取文件的权限？

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如何知道为什么我有读取文件的权限？

这是我刚刚在 CentOS SSH 帐户上注意到的内容：

统计输出 
$ stat /dev/kvm   
  File: `/dev/kvm'
  Size: 0               Blocks: 0          IO Block: 4096   character special file
Device: 5h/5d   Inode: 39768216    Links: 1     Device type: a,e8
Access: (0666/crw-rw-rw-)  Uid: (    0/    root)   Gid: (    0/    root)
Access: 2014-07-12 13:50:33.015216048 +0200
Modify: 2014-07-12 13:50:33.015216048 +0200
Change: 2014-07-12 13:50:33.015216048 +0200
身份信息 
$ id
uid=502(jacek) gid=502(jacek) groups=502(jacek)
跟踪输出 
$ strace -e open cat /dev/kvm
open("/etc/ld.so.cache", O_RDONLY)      = 3
open("/lib64/libc.so.6", O_RDONLY)      = 3
open("/usr/lib/locale/locale-archive", O_RDONLY) = 3
open("/dev/kvm", O_RDONLY)              = 3
cat: /dev/kvmopen("/usr/share/locale/locale.alias", O_RDONLY) = 4
open("/usr/share/locale/en_US.UTF-8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale/en_US.utf8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale/en_US/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale/en.UTF-8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale/en.utf8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale/en/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
: Invalid argument
访问控制列表信息 
$ getfacl /dev/kvm
getfacl: Removing leading '/' from absolute path names
# file: dev/kvm
# owner: root
# group: root
user::rw-
group::rw-
other::rw-

为什么open在这里成功了？除了 ACL 之外，还有什么机制可以用来判断用户是否可以打开文件？我可以使用哪些命令来查询它们？

答案1

我缺少什么？/dev/kvm从它的权限中可以看出，它是世界可读（和可写）的：

user::rw-
group::rw-
other::rw-

您没有理由不能阅读它。你指的是别的东西吗？

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