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I really don't understand EC2, or whether it actually uses GRUB to boot my Ubuntu server, but trying to boot my instance gives the following log output:

Fri Oct 26 17:05:57 UTC 2012: shutting down for reboot [up 18892807s].
 * Stopping web server apache2       
 ... waiting 
    [74G[ OK ]
 * Stopping DenyHosts denyhosts       
    [74G[ OK ]
Stopping DomainKeys Filter: dk-filter.
Stopping OpenDKIM: opendkim.
ossec-monitord not running ..
ossec-logcollector not running ..
ossec-syscheckd not running ..
ossec-analysisd not running ..
ossec-maild not running ..
ossec-execd not running ..
OSSEC HIDS v2.6 Stopped
 * Stopping Postfix Mail Transport Agent postfix       
    [74G[ OK ]
 * Asking all remaining processes to terminate...       
    [74G[ OK ]
 * Killing all remaining processes...       
Rather than invoking init scripts through /etc/init.d, use the service(8)
utility, e.g. service S35networking stop
initctl: Unknown job: S35networking

Since the script you are attempting to invoke has been converted to an
Upstart job, you may also use the stop(8) utility, e.g. stop S35networking
 * Deactivating swap...       
    [74G[ OK ]
 * Unmounting local filesystems...       
    [80G umount2: Device or resource busy
Xen Minimal OS!
  start_info: 0x1110000(VA)
    nr_pages: 0xf0000
  shared_inf: 0xbf214000(MA)
     pt_base: 0x1113000(VA)
nr_pt_frames: 0xd
    mfn_list: 0x990000(VA)
   mod_start: 0x0(VA)
     mod_len: 0
       flags: 0x0
    cmd_line: root=/dev/sda1 ro 4
  stack:      0x94f860-0x96f860
MM: Init
      _text: 0x0(VA)
     _etext: 0x6000d(VA)
   _erodata: 0x78000(VA)
     _edata: 0x80b00(VA)
stack start: 0x94f860(VA)
       _end: 0x98fe68(VA)
  start_pfn: 1123
    max_pfn: f0000
Mapping memory range 0x1400000 - 0xf0000000
setting 0x0-0x78000 readonly
skipped 0x1000
MM: Initialise page allocator for 189c000(189c000)-f0000000(f0000000)
MM: done
Demand map pfns at f0001000-20f0001000.
Heap resides at 20f0002000-40f0002000.
Initialising timer interface
Initialising console ... done.
gnttab_table mapped at 0xf0001000.
Initialising scheduler
Thread "Idle": pointer: 0x20f0002010, stack: 0x2050000
Initialising xenbus
Thread "xenstore": pointer: 0x20f00027c0, stack: 0x2060000
Dummy main: start_info=0x96f960
Thread "main": pointer: 0x20f0002f70, stack: 0x2070000
"main" "root=/dev/sda1" "ro" "4" 
vbd 2049 is hd0
******************* BLKFRONT for device/vbd/2049 **********

backend at /local/domain/0/backend/vbd/445/2049
Failed to read /local/domain/0/backend/vbd/445/2049/feature-barrier.
Failed to read /local/domain/0/backend/vbd/445/2049/feature-flush-cache.
16777216 sectors of 512 bytes
vbd 2064 is hd1
******************* BLKFRONT for device/vbd/2064 **********

backend at /local/domain/0/backend/vbd/445/2064
Failed to read /local/domain/0/backend/vbd/445/2064/feature-barrier.
Failed to read /local/domain/0/backend/vbd/445/2064/feature-flush-cache.
838791168 sectors of 512 bytes
vbd 2128 is hd2
******************* BLKFRONT for device/vbd/2128 **********

backend at /local/domain/0/backend/vbd/445/2128
Failed to read /local/domain/0/backend/vbd/445/2128/feature-barrier.
Failed to read /local/domain/0/backend/vbd/445/2128/feature-flush-cache.
104857600 sectors of 512 bytes


    GNU GRUB  version 0.97  (3932160K lower / 0K upper memory)

       [ Minimal BASH-like line editing is supported.   For

         the   first   word,  TAB  lists  possible  command

         completions.  Anywhere else TAB lists the possible

         completions of a device/filename. ]


Why would it drop to a grub prompt, and what do I do about this to get it to boot again?

share|improve this question
What'd you change? –  ceejayoz Oct 26 '12 at 18:44
I upgraded to 12.10 from 12.04 - it asked me if I wanted to install grub on any of my partitions, but I thought grub wasn't used for EC2. –  yuttadhammo Oct 26 '12 at 18:47
Hope you took a snapshot before upgrading. –  EEAA Oct 26 '12 at 18:47
and if I didn't? (I don't actually have access to the AWS control panel, but could have asked the guy who does - next time...) –  yuttadhammo Oct 26 '12 at 18:49
If you don't get suggestions here, you might try over on AskUbuntu.com (also a StackExchange site). –  Eric Hammond Oct 26 '12 at 19:12

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