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Troubleshoot Amazon EC2 Linux instances with failed status checks - Amazon Elastic Compute Cloud
Review status check informationRetrieve the system logsTroubleshoot system log errors for Linux instancesOut of memory: kill processERROR: mmu_update failed (Memory management update failed)I/O error (block device failure)I/O ERROR: neither local nor remote disk (Broken distributed block device)request_module: runaway loop modprobe (Looping legacy kernel modprobe on older Linux versions)"FATAL: kernel too old" and "fsck: No such file or directory while trying to open /dev" (Kernel and AMI mismatch)"FATAL: Could not load /lib/modules" or "BusyBox" (Missing kernel modules)ERROR Invalid kernel (EC2 incompatible kernel)fsck: No such file or directory while trying to open... (File system not found)General error mounting filesystems (failed mount)VFS: Unable to mount root fs on unknown-block (Root filesystem mismatch)Error: Unable to determine major/minor number of root device... (Root file system/device mismatch)XENBUS: Device with no driver...... days without being checked, check forced (File system check required)fsck died with exit status... (Missing device)GRUB prompt (grubdom>)Bringing up interface eth0: Device eth0 has different MAC address than expected, ignoring. (Hard-coded MAC address)Unable to load SELinux Policy. Machine is in enforcing mode. Halting now. (SELinux misconfiguration)XENBUS: Timeout connecting to devices (Xenbus timeout)

Troubleshoot Amazon EC2 Linux instances with failed status checks

The following information can help you troubleshoot issues if your Linux instance fails a status check. First determine whether your applications are exhibiting any problems. If you verify that the instance is not running your applications as expected, review the status check information and the system logs.

For examples of problems that can cause status checks to fail, see Status checks for Amazon EC2 instances.

Review status check information

To investigate impaired instances using the Amazon EC2 console

  1. Open the Amazon EC2 console at https://console.aws.amazon.com/ec2/.

  2. In the navigation pane, choose Instances, and then select your instance.

  3. Select the Status and alarms tab to see the individual results for all System status checks, Instance status checks, and Attached EBS status checks.

If a status check has failed, you can try one of the following options:

Retrieve the system logs

If an instance status check fails, you can reboot the instance and retrieve the system logs. The logs may reveal an error that can help you troubleshoot the issue. Rebooting clears unnecessary information from the logs.

To reboot an instance and retrieve the system log

  1. Open the Amazon EC2 console at https://console.aws.amazon.com/ec2/.

  2. In the navigation pane, choose Instances, and select your instance.

  3. Choose Instance state, Reboot instance. It might take a few minutes for your instance to reboot.

  4. Verify that the problem still exists; in some cases, rebooting may resolve the problem.

  5. When the instance is in the running state, choose Actions, Monitor and troubleshoot, Get system log.

  6. Review the log that appears on the screen, and use the list of known system log error statements below to troubleshoot your issue.

  7. If your issue is not resolved, you can post your issue to AWS re:Post.

Troubleshoot system log errors for Linux instances

For Linux instances that have failed an instance status check, such as the instance reachability check, verify that you followed the steps above to retrieve the system log. The following list contains some common system log errors and suggested actions you can take to resolve the issue for each error.

Memory Errors

Device Errors

Kernel Errors

File System Errors

Operating System Errors

Out of memory: kill process

An out-of-memory error is indicated by a system log entry similar to the one shown below.

[115879.769795] Out of memory: kill process 20273 (httpd) score 1285879
or a child 
[115879.769795] Killed process 1917 (php-cgi) vsz:467184kB, anon-
rss:101196kB, file-rss:204kB

Potential cause

Exhausted memory

Suggested actions

For this instance type Do this

Amazon EBS-backed

Do one of the following:

  • Stop the instance, and modify the instance to use a different instance type, and start the instance again. For example, a larger or a memory-optimized instance type.

  • Reboot the instance to return it to a non-impaired status. The problem will probably occur again unless you change the instance type.

Instance store-backed

Do one of the following:

  • Terminate the instance and launch a new instance, specifying a different instance type. For example, a larger or a memory-optimized instance type.

  • Reboot the instance to return it to an unimpaired status. The problem will probably occur again unless you change the instance type.

ERROR: mmu_update failed (Memory management update failed)

Memory management update failures are indicated by a system log entry similar to the following:

...
Press `ESC' to enter the menu... 0   [H[J  Booting 'Amazon Linux 2011.09 (2.6.35.14-95.38.amzn1.i686)'


root (hd0)

 Filesystem type is ext2fs, using whole disk

kernel /boot/vmlinuz-2.6.35.14-95.38.amzn1.i686 root=LABEL=/ console=hvc0 LANG=

en_US.UTF-8 KEYTABLE=us

initrd /boot/initramfs-2.6.35.14-95.38.amzn1.i686.img

ERROR: mmu_update failed with rc=-22

Potential cause

Issue with Amazon Linux

Suggested action

Post your issue to AWS re:Post or contact Support.

I/O error (block device failure)

An input/output error is indicated by a system log entry similar to the following example:

[9943662.053217] end_request: I/O error, dev sde, sector 52428288
[9943664.191262] end_request: I/O error, dev sde, sector 52428168
[9943664.191285] Buffer I/O error on device md0, logical block 209713024
[9943664.191297] Buffer I/O error on device md0, logical block 209713025
[9943664.191304] Buffer I/O error on device md0, logical block 209713026
[9943664.191310] Buffer I/O error on device md0, logical block 209713027
[9943664.191317] Buffer I/O error on device md0, logical block 209713028
[9943664.191324] Buffer I/O error on device md0, logical block 209713029
[9943664.191332] Buffer I/O error on device md0, logical block 209713030
[9943664.191339] Buffer I/O error on device md0, logical block 209713031
[9943664.191581] end_request: I/O error, dev sde, sector 52428280
[9943664.191590] Buffer I/O error on device md0, logical block 209713136
[9943664.191597] Buffer I/O error on device md0, logical block 209713137
[9943664.191767] end_request: I/O error, dev sde, sector 52428288
[9943664.191970] end_request: I/O error, dev sde, sector 52428288
[9943664.192143] end_request: I/O error, dev sde, sector 52428288
[9943664.192949] end_request: I/O error, dev sde, sector 52428288
[9943664.193112] end_request: I/O error, dev sde, sector 52428288
[9943664.193266] end_request: I/O error, dev sde, sector 52428288
...

Potential causes

Instance type Potential cause

Amazon EBS-backed

A failed Amazon EBS volume

Instance store-backed

A failed physical drive

Suggested actions

For this instance type Do this

Amazon EBS-backed

Use the following procedure:

  1. Stop the instance.

  2. Detach the volume.

  3. Attempt to recover the volume.

    Note

    It's good practice to snapshot your Amazon EBS volumes often. This dramatically decreases the risk of data loss as a result of failure.

  4. Re-attach the volume to the instance.

  5. Start the instance.

Instance store-backed

Terminate the instance and launch a new instance.

Note

Data cannot be recovered. Recover from backups.

Note

It's a good practice to use either Amazon S3 or Amazon EBS for backups. Instance store volumes are directly tied to single host and single disk failures.

I/O ERROR: neither local nor remote disk (Broken distributed block device)

An input/output error on the device is indicated by a system log entry similar to the following example:

...
block drbd1: Local IO failed in request_timer_fn. Detaching...

Aborting journal on device drbd1-8.

block drbd1: IO ERROR: neither local nor remote disk

Buffer I/O error on device drbd1, logical block 557056

lost page write due to I/O error on drbd1

JBD2: I/O error detected when updating journal superblock for drbd1-8.

Potential causes

Instance type Potential cause

Amazon EBS-backed

A failed Amazon EBS volume

Instance store-backed

A failed physical drive

Suggested action

Terminate the instance and launch a new instance.

For an Amazon EBS-backed instance you can recover data from a recent snapshot by creating an image from it. Any data added after the snapshot cannot be recovered.

request_module: runaway loop modprobe (Looping legacy kernel modprobe on older Linux versions)

This condition is indicated by a system log similar to the one shown below. Using an unstable or old Linux kernel (for example, 2.6.16-xenU) can cause an interminable loop condition at startup.

Linux version 2.6.16-xenU (builder@xenbat.amazonsa) (gcc version 4.0.1 
20050727 (Red Hat 4.0.1-5)) #1 SMP Mon May 28 03:41:49 SAST 2007

BIOS-provided physical RAM map:

 Xen: 0000000000000000 - 0000000026700000 (usable)

0MB HIGHMEM available.
...

request_module: runaway loop modprobe binfmt-464c

request_module: runaway loop modprobe binfmt-464c

request_module: runaway loop modprobe binfmt-464c

request_module: runaway loop modprobe binfmt-464c

request_module: runaway loop modprobe binfmt-464c

Suggested actions

For this instance type Do this

Amazon EBS-backed

Use a newer kernel, either GRUB-based or static, using one of the following options:

Option 1: Terminate the instance and launch a new instance, specifying the -kernel and -ramdisk parameters.

Option 2:

  1. Stop the instance.

  2. Modify the kernel and ramdisk attributes to use a newer kernel.

  3. Start the instance.

Instance store-backed

Terminate the instance and launch a new instance, specifying the -kernel and -ramdisk parameters.

"FATAL: kernel too old" and "fsck: No such file or directory while trying to open /dev" (Kernel and AMI mismatch)

This condition is indicated by a system log similar to the one shown below.

Linux version 2.6.16.33-xenU (root@dom0-0-50-45-1-a4-ee.z-2.aes0.internal) 
(gcc version 4.1.1 20070105 (Red Hat 4.1.1-52)) #2 SMP Wed Aug 15 17:27:36 SAST 2007
...
FATAL: kernel too old
Kernel panic - not syncing: Attempted to kill init!

Potential causes

Incompatible kernel and userland

Suggested actions

For this instance type Do this

Amazon EBS-backed

Use the following procedure:

  1. Stop the instance.

  2. Modify the configuration to use a newer kernel.

  3. Start the instance.

Instance store-backed

Use the following procedure:

  1. Create an AMI that uses a newer kernel.

  2. Terminate the instance.

  3. Start a new instance from the AMI you created.

"FATAL: Could not load /lib/modules" or "BusyBox" (Missing kernel modules)

This condition is indicated by a system log similar to the one shown below.

[    0.370415] Freeing unused kernel memory: 1716k freed 
Loading, please wait...
WARNING: Couldn't open directory /lib/modules/2.6.34-4-virtual: No such file or directory
FATAL: Could not open /lib/modules/2.6.34-4-virtual/modules.dep.temp for writing: No such file or directory
FATAL: Could not load /lib/modules/2.6.34-4-virtual/modules.dep: No such file or directory
Couldn't get a file descriptor referring to the console
Begin: Loading essential drivers... ...
FATAL: Could not load /lib/modules/2.6.34-4-virtual/modules.dep: No such file or directory
FATAL: Could not load /lib/modules/2.6.34-4-virtual/modules.dep: No such file or directory
Done.
Begin: Running /scripts/init-premount ...
Done.
Begin: Mounting root file system... ...
Begin: Running /scripts/local-top ...
Done.
Begin: Waiting for root file system... ...
Done.
Gave up waiting for root device.  Common problems:
 - Boot args (cat /proc/cmdline)
   - Check rootdelay= (did the system wait long enough?)
   - Check root= (did the system wait for the right device?)
 - Missing modules (cat /proc/modules; ls /dev)
FATAL: Could not load /lib/modules/2.6.34-4-virtual/modules.dep: No such file or directory
FATAL: Could not load /lib/modules/2.6.34-4-virtual/modules.dep: No such file or directory
ALERT! /dev/sda1 does not exist. Dropping to a shell!


BusyBox v1.13.3 (Ubuntu 1:1.13.3-1ubuntu5) built-in shell (ash)
Enter 'help' for a list of built-in commands.

(initramfs)

Potential causes

One or more of the following conditions can cause this problem:

  • Missing ramdisk

  • Missing correct modules from ramdisk

  • Amazon EBS root volume not correctly attached as /dev/sda1

Suggested actions

For this instance type Do this

Amazon EBS-backed

Use the following procedure:

  1. Select corrected ramdisk for the Amazon EBS volume.

  2. Stop the instance.

  3. Detach the volume and repair it.

  4. Attach the volume to the instance.

  5. Start the instance.

  6. Modify the AMI to use the corrected ramdisk.

Instance store-backed

Use the following procedure:

  1. Terminate the instance and launch a new instance with the correct ramdisk.

  2. Create a new AMI with the correct ramdisk.

ERROR Invalid kernel (EC2 incompatible kernel)

This condition is indicated by a system log similar to the one shown below.

...
root (hd0)

 Filesystem type is ext2fs, using whole disk

kernel /vmlinuz root=/dev/sda1 ro

initrd /initrd.img

ERROR Invalid kernel: elf_xen_note_check: ERROR: Will only load images 
built for the generic loader or Linux images
xc_dom_parse_image returned -1

Error 9: Unknown boot failure

  Booting 'Fallback'
  
root (hd0)

 Filesystem type is ext2fs, using whole disk

kernel /vmlinuz.old root=/dev/sda1 ro

Error 15: File not found

Potential causes

One or both of the following conditions can cause this problem:

  • Supplied kernel is not supported by GRUB

  • Fallback kernel does not exist

Suggested actions

For this instance type Do this

Amazon EBS-backed

Use the following procedure:

  1. Stop the instance.

  2. Replace with working kernel.

  3. Install a fallback kernel.

  4. Modify the AMI by correcting the kernel.

Instance store-backed

Use the following procedure:

  1. Terminate the instance and launch a new instance with the correct kernel.

  2. Create an AMI with the correct kernel.

  3. (Optional) Seek technical assistance for data recovery using Support.

fsck: No such file or directory while trying to open... (File system not found)

This condition is indicated by a system log similar to the one shown below.

		Welcome to Fedora 
		Press 'I' to enter interactive startup.
Setting clock : Wed Oct 26 05:52:05 EDT 2011 [  OK  ]

Starting udev: [  OK  ]

Setting hostname localhost:  [  OK  ]

No devices found
Setting up Logical Volume Management: File descriptor 7 left open
  No volume groups found
[  OK  ]

Checking filesystems
Checking all file systems.
[/sbin/fsck.ext3 (1) -- /] fsck.ext3 -a /dev/sda1 
/dev/sda1: clean, 82081/1310720 files, 2141116/2621440 blocks
[/sbin/fsck.ext3 (1) -- /mnt/dbbackups] fsck.ext3 -a /dev/sdh 
fsck.ext3: No such file or directory while trying to open /dev/sdh

/dev/sdh: 
The superblock could not be read or does not describe a correct ext2
filesystem.  If the device is valid and it really contains an ext2
filesystem (and not swap or ufs or something else), then the superblock
is corrupt, and you might try running e2fsck with an alternate superblock:
    e2fsck -b 8193 <device>

[FAILED]


*** An error occurred during the file system check.
*** Dropping you to a shell; the system will reboot
*** when you leave the shell.
Give root password for maintenance
(or type Control-D to continue):

Potential causes

  • A bug exists in ramdisk filesystem definitions /etc/fstab

  • Misconfigured filesystem definitions in /etc/fstab

  • Missing/failed drive

Suggested actions

For this instance type Do this

Amazon EBS-backed

Use the following procedure:

  1. Stop the instance, detach the root volume, repair/modify /etc/fstab the volume, attach the volume to the instance, and start the instance.

  2. Fix ramdisk to include modified /etc/fstab (if applicable).

  3. Modify the AMI to use a newer ramdisk.

The sixth field in the fstab defines availability requirements of the mount – a nonzero value implies that an fsck will be done on that volume and must succeed. Using this field can be problematic in Amazon EC2 because a failure typically results in an interactive console prompt that is not currently available in Amazon EC2. Use care with this feature and read the Linux man page for fstab.

Instance store-backed

Use the following procedure:

  1. Terminate the instance and launch a new instance.

  2. Detach any errant Amazon EBS volumes and the reboot instance.

  3. (Optional) Seek technical assistance for data recovery using Support.

General error mounting filesystems (failed mount)

This condition is indicated by a system log similar to the one shown below.

Loading xenblk.ko module 
xen-vbd: registered block device major 8

Loading ehci-hcd.ko module
Loading ohci-hcd.ko module
Loading uhci-hcd.ko module
USB Universal Host Controller Interface driver v3.0

Loading mbcache.ko module
Loading jbd.ko module
Loading ext3.ko module
Creating root device.
Mounting root filesystem.
kjournald starting.  Commit interval 5 seconds

EXT3-fs: mounted filesystem with ordered data mode.

Setting up other filesystems.
Setting up new root fs
no fstab.sys, mounting internal defaults
Switching to new root and running init.
unmounting old /dev
unmounting old /proc
unmounting old /sys
mountall:/proc: unable to mount: Device or resource busy
mountall:/proc/self/mountinfo: No such file or directory
mountall: root filesystem isn't mounted
init: mountall main process (221) terminated with status 1

General error mounting filesystems.
A maintenance shell will now be started.
CONTROL-D will terminate this shell and re-try.
Press enter for maintenance
(or type Control-D to continue):

Potential causes

Instance type Potential cause

Amazon EBS-backed

  • Detached or failed Amazon EBS volume.

  • Corrupted filesystem.

  • Mismatched ramdisk and AMI combination (such as Debian ramdisk with a SUSE AMI).

Instance store-backed

  • A failed drive.

  • A corrupted file system.

  • A mismatched ramdisk and combination (for example, a Debian ramdisk with a SUSE AMI).

Suggested actions

For this instance type Do this

Amazon EBS-backed

Use the following procedure:

  1. Stop the instance.

  2. Detach the root volume.

  3. Attach the root volume to a known working instance.

  4. Run filesystem check (fsck -a /dev/...).

  5. Fix any errors.

  6. Detach the volume from the known working instance.

  7. Attach the volume to the stopped instance.

  8. Start the instance.

  9. Recheck the instance status.

Instance store-backed

Try one of the following:

  • Start a new instance.

  • (Optional) Seek technical assistance for data recovery using Support.

VFS: Unable to mount root fs on unknown-block (Root filesystem mismatch)

This condition is indicated by a system log similar to the one shown below.