linux - 即使是 root 也不允许读取文件操作

Question

我下载了一个OctoPi并将文件解压缩到我的本地文件系统 (EXT4) 中:

$ unzip 2014-09-09-wheezy-octopi-0.10.0.zip

只有一个文件被解压:

-rwxrwxr-x 1 user  user  3276800000 Oct 27 14:46 2014-09-09-wheezy-octopi-0.10.0.img

现在我想为 SD 卡使用图像，但即使 cat 文件写入错误(现在作为 root，我之前与用户试过):

# cat 2014-09-09-wheezy-octopi-0.10.0.img 
cat: 2014-09-09-wheezy-octopi-0.10.0.img: Operation not permitted

我尝试将它解压缩到另一个位置(不同的文件系统、USB 内存棒)，但它具有相同的行为。 我也试过 strace:

# strace cat 2014-09-09-wheezy-octopi-0.10.0.img 
execve("/bin/cat", ["cat", "2014-09-09-wheezy-octopi-0.10.0."...], [/* 27 vars */]) = 0
brk(0)                                  = 0x718000
access("/etc/ld.so.nohwcap", F_OK)      = -1 ENOENT (No such file or directory)
mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f1fb2a65000
access("/etc/ld.so.preload", R_OK)      = -1 ENOENT (No such file or directory)
open("/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=166255, ...}) = 0
mmap(NULL, 166255, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7f1fb2a3c000
close(3)                                = 0
access("/etc/ld.so.nohwcap", F_OK)      = -1 ENOENT (No such file or directory)
open("/lib/x86_64-linux-gnu/libc.so.6", O_RDONLY|O_CLOEXEC) = 3
read(3, "\177ELF\2\1\1\3\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\320\37\2\0\0\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0755, st_size=1844160, ...}) = 0
mmap(NULL, 3949184, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f1fb2480000
mprotect(0x7f1fb263a000, 2097152, PROT_NONE) = 0
mmap(0x7f1fb283a000, 24576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1ba000) = 0x7f1fb283a000
mmap(0x7f1fb2840000, 17024, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7f1fb2840000
close(3)                                = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f1fb2a3b000
mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f1fb2a39000
arch_prctl(ARCH_SET_FS, 0x7f1fb2a39740) = 0
mprotect(0x7f1fb283a000, 16384, PROT_READ) = 0
mprotect(0x60b000, 4096, PROT_READ)     = 0
mprotect(0x7f1fb2a67000, 4096, PROT_READ) = 0
munmap(0x7f1fb2a3c000, 166255)          = 0
brk(0)                                  = 0x718000
brk(0x739000)                           = 0x739000
open("/usr/lib/locale/locale-archive", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=3165552, ...}) = 0
mmap(NULL, 3165552, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7f1fb217b000
close(3)                                = 0
fstat(1, {st_mode=S_IFCHR|0600, st_rdev=makedev(136, 1), ...}) = 0
open("2014-09-09-wheezy-octopi-0.10.0.img", O_RDONLY) = -1 EPERM (Operation not permitted)
write(2, "cat: ", 5cat: )                    = 5
write(2, "2014-09-09-wheezy-octopi-0.10.0."..., 352014-09-09-wheezy-octopi-0.10.0.img) = 35
open("/usr/share/locale/locale.alias", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=2570, ...}) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f1fb2a64000
read(3, "# Locale name alias data base.\n#"..., 4096) = 2570
read(3, "", 4096)                       = 0
close(3)                                = 0
munmap(0x7f1fb2a64000, 4096)            = 0
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)
open("/usr/share/locale-langpack/en_US.UTF-8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale-langpack/en_US.utf8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale-langpack/en_US/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale-langpack/en.UTF-8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale-langpacsudo k/en.utf8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale-langpack/en/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
write(2, ": Operation not permitted", 25: Operation not permitted) = 25
write(2, "\n", 1
)                       = 1
close(1)                                = 0
close(2)                                = 0
exit_group(1)                           = ?
+++ exited with 1 +++

在不同的系统上(只检查了一个)我能够阅读它。

我有最新更新的 Kubuntu 14.10 x64。 Linux mycomp 3.16.0-28-generic#38-Ubuntu SMP Fri Dec 12 17:37:40 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux

实际上我通过管道写图像(它有效):

unzip -p ... | pv | dd ...

但我想知道，为什么文件不可读以及我哪里弄错了。

....

后来我对rapsbian也有同样的经历:

wget -O 2014-12-24-wheezy-raspbian.zip http://downloads.raspberrypi.org/raspbian_latest

Answer 1

重命名

mv 2014-09-09-wheezy-octopi-0.10.0.img initrd.gz

然后解压