linux – 为什么mkfs在Ubuntu 12.04上的RAID分区上覆盖LVM上的LU

我正在尝试设置几个LUKS加密分区,以便在启动时安装到新的Ubuntu服务器上,该服务器在软件RAID之上安装了LVM.运行cryptsetup luksFormat后,LUKS标头在卷上清晰可见.在运行任何类型的mkfs之后,将覆盖标头(在没有LVM的情况下设置的其他系统上不会发生这种情况),并且cryptsetup将不再将该设备识别为LUKS设备.

# cryptsetup -y --cipher aes-cbc-essiv:sha256 --key-size 256 luksFormat /dev/dm-1
WARNING!
========
This will overwrite data on /dev/dm-1 irrevocably.

Are you sure? (Type uppercase yes): YES
Enter LUKS passphrase: 
Verify passphrase:
# hexdump -C /dev/dm-1|head -n5
00000000  4c 55 4b 53 ba be 00 01  61 65 73 00 00 00 00 00  |LUKS....aes.....|
00000010  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000020  00 00 00 00 00 00 00 00  63 62 63 2d 65 73 73 69  |........cbc-essi|
00000030  76 3a 73 68 61 32 35 36  00 00 00 00 00 00 00 00  |v:sha256........|
00000040  00 00 00 00 00 00 00 00  73 68 61 31 00 00 00 00  |........sha1....|
# cryptsetup luksOpen /dev/dm-1 web2-var
# mkfs.ext4 /dev/mapper/web2-var
[..snip..]
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done   
# hexdump -C /dev/dm-1|head -n5
# cryptsetup luksClose /dev/mapper/web2-var
00000000  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00000400  00 40 5d 00 00 88 74 01  66 a0 12 00 17 f2 6d 01  |.@]...t.f.....m.|
00000410  f5 3f 5d 00 00 00 00 00  02 00 00 00 02 00 00 00  |.?].............|
00000420  00 80 00 00 00 80 00 00  00 20 00 00 00 00 00 00  |......... ......|
# cryptsetup luksOpen /dev/dm-1 web2-var
Device /dev/dm-1 is not a valid LUKS device.

我也尝试过mkfs.ext2,结果相同.基于我在Debian和Ubuntu(但不是LVM或Ubuntu 12.04)上成功完成的设置,很难理解为什么会失败.

cryptsetup luksOpen /dev/dm-1 web2-var_crypt