简短版本：rackspace (xen) VM 上的 ext3 根文件系统在启动时检测到中止的日志并以只读方式挂载。我尝试按照我读过的许多文章中的规定从救援环境中修复此问题tune2fs，e2fsck但错误仍然发生。
更新: 所以基于本文我将“barrier=0”添加到/etc/fstab该文件系统的条目中，并在下次启动时以读写方式正常安装。我相信这是一个半虚拟化的事情，但如果有人完全理解这里发生的事情并能够解释的话，我会很高兴。
长版：
Rackspace VM 刚刚从 Ubuntu 11.10 升级到 12.04.2
dmesg 输出错误：
[ 14.701446] blkfront: barrier: empty write xvda op failed
[ 14.701452] blkfront: xvda: barrier or flush: disabled
[ 14.701460] end_request: I/O error, dev xvda, sector 28175816
[ 14.701473] end_request: I/O error, dev xvda, sector 28175816
[ 14.701487] Aborting journal on device xvda1.
[ 14.704186] EXT3-fs (xvda1): error: ext3_journal_start_sb: Detected aborted journal
[ 14.704199] EXT3-fs (xvda1): error: remounting filesystem read-only
[ 14.940734] init: dmesg main process (763) terminated with status 7
[ 18.425994] init: mongodb main process (769) terminated with status 1
[ 21.940032] eth1: no IPv6 routers present
[ 23.612044] eth0: no IPv6 routers present
[ 27.147759] [UFW BLOCK] IN=eth0 OUT= MAC=40:40:73:00:ea:12:c4:71:fe:f1:e1:3f:08:00 SRC=98.143.36.192 DST=50.56.240.11 LEN=40 TOS=0x00 PREC=0x00 TTL=242 ID=37934 DF PROTO=TCP SPT=30269 DPT=8123 WINDOW=512 RES=0x00 SYN URGP=0
[ 31.025920] [UFW BLOCK] IN=eth0 OUT= MAC=40:40:73:00:ea:12:c4:71:fe:f1:e1:3f:08:00 SRC=116.6.60.9 DST=50.56.240.11 LEN=40 TOS=0x00 PREC=0x00 TTL=101 ID=256 PROTO=TCP SPT=6000 DPT=1433 WINDOW=16384 RES=0x00 SYN URGP=0
[ 493.974612] EXT3-fs (xvda1): error: ext3_remount: Abort forced by user
[ 505.887555] EXT3-fs (xvda1): error: ext3_remount: Abort forced by user
在救援操作系统中，我尝试过：
tune2sf -O ^has_journal /dev/xdbb1 #Device is xvdb1 in rescue, but xvdba1 in real OS
e2fsck -f /dev/xvdb1
tune2sf -j /dev/xvdb1
我也跑过e2fsck -p、e2fsck -f、 和tune2fs -e continue。这是 的输出tune2fs -l。
tune2fs 1.41.14 (22-Dec-2010)
Filesystem volume name: <none>
Last mounted on: <not available>
Filesystem UUID: 68910771-4026-4588-a62a-54eb992f4c6e
Filesystem magic number: 0xEF53
Filesystem revision #: 1 (dynamic)
Filesystem features: has_journal ext_attr resize_inode dir_index filetype sparse_super large_file
Filesystem flags: signed_directory_hash
Default mount options: (none)
Filesystem state: clean
Errors behavior: Continue
Filesystem OS type: Linux
Inode count: 1245184
Block count: 4980480
Reserved block count: 199219
Free blocks: 2550830
Free inodes: 1025001
First block: 0
Block size: 4096
Fragment size: 4096
Reserved GDT blocks: 606
Blocks per group: 32768
Fragments per group: 32768
Inodes per group: 8192
Inode blocks per group: 512
Filesystem created: Thu Oct 20 21:34:53 2011
Last mount time: Mon Apr 8 23:01:13 2013
Last write time: Mon Apr 8 23:08:09 2013
Mount count: 0
Maximum mount count: 29
Last checked: Mon Apr 8 23:04:49 2013
Check interval: 15552000 (6 months)
Next check after: Sat Oct 5 23:04:49 2013
Reserved blocks uid: 0 (user root)
Reserved blocks gid: 0 (group root)
First inode: 11
Inode size: 256
Required extra isize: 28
Desired extra isize: 28
Journal inode: 8
Default directory hash: half_md4
Directory Hash Seed: 1e07317a-6301-41d9-8885-0e3e837f2a38
Journal backup: inode blocks
/var/log/syslog我还用 grep 了救援模式下的一些行以及一些额外的错误信息：
Apr 8 19:47:06 dev kernel: [26504959.895754] blkfront: barrier: empty write xvda op failed
Apr 8 19:47:06 dev kernel: [26504959.895763] blkfront: xvda: barrier or flush: disabled
Apr 8 20:19:33 dev kernel: [ 0.000000] Command line: root=/dev/xvda1 console=hvc0 ro quiet splash
Apr 8 20:19:33 dev kernel: [ 0.000000] Kernel command line: root=/dev/xvda1 console=hvc0 ro quiet splash
Apr 8 20:19:33 dev kernel: [ 0.240303] blkfront: xvda: barrier: enabled
Apr 8 20:19:33 dev kernel: [ 0.249960] xvda: xvda1
Apr 8 20:19:33 dev kernel: [ 0.250356] xvda: detected capacity change from 0 to 20401094656
Apr 8 20:19:33 dev kernel: [ 5.684101] EXT3-fs (xvda1): mounted filesystem with ordered data mode
Apr 8 20:19:33 dev kernel: [ 140.547468] blkfront: barrier: empty write xvda op failed
Apr 8 20:19:33 dev kernel: [ 140.547477] blkfront: xvda: barrier or flush: disabled
Apr 8 20:19:33 dev kernel: [ 140.709985] EXT3-fs (xvda1): using internal journal
Apr 8 21:18:12 dev kernel: [ 0.000000] Command line: root=/dev/xvda1 console=hvc0 ro quiet splash
Apr 8 21:18:12 dev kernel: [ 0.000000] Kernel command line: root=/dev/xvda1 console=hvc0 ro quiet splash
Apr 8 21:18:12 dev kernel: [ 1.439023] blkfront: xvda: barrier: enabled
Apr 8 21:18:12 dev kernel: [ 1.454307] xvda: xvda1
Apr 8 21:18:12 dev kernel: [ 6.799014] EXT3-fs (xvda1): recovery required on readonly filesystem
Apr 8 21:18:12 dev kernel: [ 6.799020] EXT3-fs (xvda1): write access will be enabled during recovery
Apr 8 21:18:12 dev kernel: [ 6.839498] blkfront: barrier: empty write xvda op failed
Apr 8 21:18:12 dev kernel: [ 6.839505] blkfront: xvda: barrier or flush: disabled
Apr 8 21:18:12 dev kernel: [ 6.854814] EXT3-fs (xvda1): warning: ext3_clear_journal_err: Filesystem error recorded from previous mount: IO failure
Apr 8 21:18:12 dev kernel: [ 6.854820] EXT3-fs (xvda1): warning: ext3_clear_journal_err: Marking fs in need of filesystem check.
Apr 8 21:18:12 dev kernel: [ 6.855247] EXT3-fs (xvda1): recovery complete
Apr 8 21:18:12 dev kernel: [ 6.855902] EXT3-fs (xvda1): mounted filesystem with ordered data mode
Apr 8 21:18:12 dev kernel: [ 143.505890] EXT3-fs (xvda1): using internal journal
答案1
此时我认为这很可能是一个例子Debian 错误 637234。由于这是一个云虚拟机，虚拟机管理程序内核不在我的控制范围内。解决方法是使用barrier=0in/etc/fstab作为根文件系统。长期解决方案是将盒子重建为下一代机架空间云实例，而不是第一代基于 Xen 的实例。
答案2
/etc/fstab 中的“barrier=0”可能为时已晚（并且在文件系统在稍后的引导阶段挂载 RW 后才开始发挥作用）。
“barrier=off”作为附加内核参数应该更早更好地工作。
尝试一下。如果您的 DomU 是由 pygrub 从 Dom0 启动的（这是“通常”方式），您可以将其放入 DomU 中的 grub-kernel-configuration-line 中。