Re: [Qemu-discuss] Issue related to mounting /dev/nbd0p1

[Jan Schermer]

Partigion is missing :-)
try:
kpartx -a /dev/ndb0


> On 4 Dec 2018, at 11:35, ramakanth varala <address@hidden> wrote:
> 
> Hi Pascal..
> 
> yes its RW ...
> 
> address@hidden ~]# fdisk -l /dev/nbd0
> 
> Disk /dev/nbd0: 21.4 GB, 21474836480 bytes
> 255 heads, 63 sectors/track, 2610 cylinders
> Units = cylinders of 16065 * 512 = 8225280 bytes
> 
>     Device Boot      Start         End      Blocks   Id  System
> /dev/nbd0p1               1          13      104391   83  Linux
> /dev/nbd0p2            2610        2610        8032+  83  Linux
> 
> address@hidden ~]# ls -ltr /dev/nbd0*
> brw-r----- 1 root disk 43, 0 Dec  4 11:06 /dev/nbd0
> 
> address@hidden ~]# mount /dev/nbd0p1 /home/test/test.3.5.1b.debug/mnt/boot/
> mount: special device /dev/nbd0p1 does not exist
> 
> address@hidden ~]# cat /proc/partitions
> major minor  #blocks  name
> 
>   8     0   62914560 sda
>   8     1     104391 sda1
>   8     2   62806117 sda2
> 253     0   56655872 dm-0
> 253     1    6127616 dm-1
> 253     2     104391 dm-2
> 253     3   20860402 dm-3
> 
> 
> --Not sure..what's missing..
> 
> Thanks
> Rama Kanth
> 
> On Tue, Dec 4, 2018 at 3:07 PM Pascal <address@hidden> wrote:
> 
>> hi,
>> 
>> you left fdisk without saving the changes (w before q), so there can't be
>> two partitions.
>> on the other hand, we should find the existing partition...
>> there is a strange warning when fdisk starts: what is on the over side of
>> nbd0 ?
>> is /dev/nbd0 rw ?
>> if you can't re-read the partitions table, can you disconnect /dev/nbd0 and
>> then reconnect it ?
>> 
>> 
>> Le lun. 3 déc. 2018 à 16:17, ramakanth varala <address@hidden>
>> a écrit :
>> 
>>> Hi ,
>>> 
>>> I tried below steps .. still with some errors..
>>> 
>>> 
>>> address@hidden ~]# fdisk /dev/nbd0
>>> 
>>> The number of cylinders for this disk is set to 2610.
>>> There is nothing wrong with that, but this is larger than 1024,
>>> and could in certain setups cause problems with:
>>> 1) software that runs at boot time (e.g., old versions of LILO)
>>> 2) booting and partitioning software from other OSs
>>>   (e.g., DOS FDISK, OS/2 FDISK)
>>> 
>>> Command (m for help): n
>>> Command action
>>>   e   extended
>>>   p   primary partition (1-4)
>>> p
>>> Partition number (1-4): 1
>>> Partition 1 is already defined.  Delete it before re-adding it.
>>> 
>>> Command (m for help): d
>>> Partition number (1-4): 1
>>> 
>>> Command (m for help): d
>>> Selected partition 2
>>> 
>>> Command (m for help): p
>>> 
>>> Disk /dev/nbd0: 21.4 GB, 21474836480 bytes
>>> 255 heads, 63 sectors/track, 2610 cylinders
>>> Units = cylinders of 16065 * 512 = 8225280 bytes
>>> 
>>>     Device Boot      Start         End      Blocks   Id  System
>>> 
>>> Command (m for help): n
>>> Command action
>>>   e   extended
>>>   p   primary partition (1-4)
>>> p
>>> Partition number (1-4): 1
>>> First cylinder (1-2610, default 1):
>>> Using default value 1
>>> Last cylinder or +size or +sizeM or +sizeK (1-2610, default 2610): 4
>>> 
>>> Command (m for help): n
>>> Command action
>>>   e   extended
>>>   p   primary partition (1-4)
>>> p
>>> Partition number (1-4): 2
>>> First cylinder (5-2610, default 5):
>>> Using default value 5
>>> Last cylinder or +size or +sizeM or +sizeK (5-2610, default 2610):
>>> Using default value 2610
>>> 
>>> Command (m for help): p
>>> 
>>> Disk /dev/nbd0: 21.4 GB, 21474836480 bytes
>>> 255 heads, 63 sectors/track, 2610 cylinders
>>> Units = cylinders of 16065 * 512 = 8225280 bytes
>>> 
>>>     Device Boot      Start         End      Blocks   Id  System
>>> /dev/nbd0p1               1           4       32098+  83  Linux
>>> /dev/nbd0p2               5        2610    20932695   83  Linux
>>> 
>>> Command (m for help): q
>>> 
>>> address@hidden ~]# blockdev --rereadpt /dev/nbd0
>>> BLKRRPART: Invalid argument
>>> address@hidden ~]# ls /dev/nbd0
>>> /dev/nbd0
>>> address@hidden ~]# ls /dev/nbd0*
>>> /dev/nbd0
>>> 
>>> 
>>> 
>>> Thanks
>>> Rama Kanth
>>> 
>>> On Fri, Nov 30, 2018 at 6:48 PM Pascal <address@hidden> wrote:
>>> 
>>>> do not create nodes manually but with fdisk on nbd0 :
>>>> 
>>>> # fdisk /dev/nbd0
>>>> ## now create your partitions in fdisk
>>>> ## use w to write changes and q to quit fdisk
>>>> 
>>>> # blocdev --rereadpt /dev/nbd0
>>>> 
>>>> # ls /dev/nbd0*
>>>> ## you will now have /dev/nbd0, /dev/nbd0p1 and /dev/nbd0p2
>>>> 
>>>> if this is not the case while the fdisk command ended without error :
>>>> 
>>>> # sync
>>>> # qemu-nbd -d /dev/nbd0
>>>> # qemu-nbd -c /dev/nbd0 /the/target
>>>> 
>>>> 
>>>> Le ven. 30 nov. 2018 à 14:04, ramakanth varala <
>>>> address@hidden>
>>>> a écrit :
>>>> 
>>>>> Hi Pascal & Jakob,
>>>>> 
>>>>> I started from first .
>>>>> 
>>>>> I created manully the partitions as below
>>>>> 
>>>>>   27  mknod /dev/nbd0p1 b 1 4
>>>>>   28  mknod /dev/nbd0p2 b 1 4
>>>>> 
>>>>> still in /proc/partitions i don't see any info , it shows as below
>>>>> 
>>>>> address@hidden ~]# cat /proc/partitions
>>>>> major minor  #blocks  name
>>>>> 
>>>>>   8     0   62914560 sda
>>>>>   8     1     104391 sda1
>>>>>   8     2   62806117 sda2
>>>>> 253     0   56655872 dm-0
>>>>> 253     1    6127616 dm-1
>>>>> 
>>>>> address@hidden ~]# fdisk  -l /dev/nbd0
>>>>> 
>>>>> Disk /dev/nbd0: 21.4 GB, 21474836480 bytes
>>>>> 255 heads, 63 sectors/track, 2610 cylinders
>>>>> Units = cylinders of 16065 * 512 = 8225280 bytes
>>>>> 
>>>>>     Device Boot      Start         End      Blocks   Id  System
>>>>> /dev/nbd0p1   *           1          13      104391   83  Linux
>>>>> /dev/nbd0p2              14        2610    20860402+  8e  Linux LVM
>>>>> 
>>>>> 
>>>>> when i try for mount , i see below error
>>>>> 
>>>>> 
>>>>> address@hidden ~]# mount /dev/nbd0p1
>>>>> /home/test/test.3.5.1b.debug/mnt/boot
>>>>> mount: you must specify the filesystem type
>>>>> 
>>>>> i tried to give file system type as below, still issues.
>>>>> 
>>>>> address@hidden ~]# mount -t ext3 /dev/nbd0p1
>>>>> /home/test/test.3.5.1b.debug/mnt/boot
>>>>> mount: wrong fs type, bad option, bad superblock on /dev/nbd0p1,
>>>>>       missing codepage or other error
>>>>>       In some cases useful info is found in syslog - try
>>>>>       dmesg | tail  or so
>>>>> 
>>>>> 
>>>>> Any inputs would be really helpfull..
>>>>> 
>>>>> 
>>>>> Thanks
>>>>> Rama Kanth
>>>>> 
>>>>> On Fri, Nov 30, 2018 at 1:50 PM Pascal <address@hidden> wrote:
>>>>> 
>>>>>> restart from zero if possible...
>>>>>> 
>>>>>> # qemu-nbd -d /dev/nbd0
>>>>>> # modprobe -rv nbd
>>>>>> 
>>>>>> # modprobe nbd
>>>>>> # qemu-nbd -c /dev/nbd0 /the/file
>>>>>> # blockdev --rereadpt /dev/nbd0
>>>>>> # fdisk -l /dev/nbd0
>>>>>> # mount /dev/nbd0p1 /mount/point
>>>>>> 
>>>>>> Le jeu. 29 nov. 2018 à 17:32, Jakob Bohm <address@hidden> a
>>>>>> écrit :
>>>>>> 
>>>>>>> Check
>>>>>>> 
>>>>>>>    cat /proc/partitions
>>>>>>> 
>>>>>>> If the partitions are not listed there, the kernel does not
>>>>>>> recognize them, perhaps the kernel doesn't recognize that
>>>>>>> nbd0 is a "partitionable disk", and thus does not create the
>>>>>>> internal nbd0p1 and ndb0p2 devices.
>>>>>>> 
>>>>>>> If the partitions are listed there, you just need to create the
>>>>>>> actual /dev/nbd0p1 and /dev/nbd0p2 file names with mknod or
>>>>>>> figure out why your "/dev/" management software (maybe udev,
>>>>>>> maybe something better) doesn't do that for you.
>>>>>>> 
>>>>>>> On 29/11/2018 12:46, ramakanth varala wrote:
>>>>>>>> Still with some errors..
>>>>>>>> 
>>>>>>>> address@hidden ~]# kpartx -a /dev/nbd0
>>>>>>>> read error, sector 0
>>>>>>>> read error, sector 1
>>>>>>>> read error, sector 29
>>>>>>>> address@hidden ~]# ls /dev/nbd
>>>>>>>> nbd0   nbd1   nbd10  nbd11  nbd12  nbd13  nbd14  nbd15  nbd2
>> nbd3
>>>>>>> nbd4
>>>>>>>>  nbd5   nbd6   nbd7   nbd8   nbd9
>>>>>>>> 
>>>>>>>> 
>>>>>>>> 
>>>>>>>> On Thu, Nov 29, 2018 at 4:22 PM Nerijus Baliūnas <
>>>>>>>> address@hidden> wrote:
>>>>>>>> 
>>>>>>>>> Please try kpartx -a /dev/nbd0
>>>>>>>>> 
>>>>>>>>> 2018-11-29 12:38, ramakanth varala rašė:
>>>>>>>>>> thanks for the reply ..
>>>>>>>>>> 
>>>>>>>>>> But i get below error when i do ..
>>>>>>>>>> 
>>>>>>>>>> 
>>>>>>>>>> address@hidden ~]# partx -a /dev/nbd0
>>>>>>>>>> HDIO_GETGEO: Inappropriate ioctl for device
>>>>>>>>>> 
>>>>>>>>>> On Thu, Nov 29, 2018 at 4:04 PM Nerijus Baliūnas <
>>>>>>>>>> address@hidden> wrote:
>>>>>>>>>> 
>>>>>>>>>>> 2018-11-29 12:10, ramakanth varala rašė:
>>>>>>>>>>>> address@hidden ~]# mount /dev/nbd0p1
>>>>>> /home/test.1.3.debug/mnt/boot
>>>>>>>>>>>> mount: special device /dev/nbd0p1 does not exist
>>>>>>>>>>> partx -a /dev/nbd0
>>>>>>>>>>> 
>>>>>>> 
>>>>>>> 
>>>>>>> Enjoy
>>>>>>> 
>>>>>>> Jakob
>>>>>>> --
>>>>>>> Jakob Bohm, CIO, Partner, WiseMo A/S.  https://www.wisemo.com
>>>>>>> Transformervej 29, 2860 Søborg, Denmark.  Direct +45 31 13 16 10
>>>>>>> This public discussion message is non-binding and may contain
>> errors.
>>>>>>> WiseMo - Remote Service Management for PCs, Phones and Embedded
>>>>>>> 
>>>>>>> 
>>>>>>> 
>>>>>> 
>>>>> 
>>>> 
>>> 
>>