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Old 11-11-2016, 06:12 AM   #1
sahruk
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Unhappy home partition doesn't mount after resizing using lvreduce - can't read superblock


Hello,

I reduced home partition using command below:
Code:
[root@sfvm08 mapper]# lvreduce -L 70G /dev/mapper/centos_sfvm03-home
  WARNING: Reducing active and open logical volume to 70.00 GiB
  THIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce home? [y/n]: y
  Size of logical volume centos_sfvm03/home changed from 97.45 GiB (24946 extents) to 70.00 GiB (17920 extents).
  Logical volume home successfully resized.
and as seems I get success message.

after that I increased root partition using command below:
Code:
[root@sfvm08 mapper]# lvextend -r -l+100%FREE /dev/mapper/centos_sfvm03-root
  Size of logical volume centos_sfvm03/root changed from 50.00 GiB (12800 extents) to 77.51 GiB (19842 extents).
  Logical volume root successfully resized.
meta-data=/dev/mapper/centos_sfvm03-root isize=256    agcount=4, agsize=3276800 blks
         =                       sectsz=512   attr=2, projid32bit=1
         =                       crc=0        finobt=0
data     =                       bsize=4096   blocks=13107200, imaxpct=25
         =                       sunit=0      swidth=0 blks
naming   =version 2              bsize=4096   ascii-ci=0 ftype=0
log      =internal               bsize=4096   blocks=6400, version=2
         =                       sectsz=512   sunit=0 blks, lazy-count=1
realtime =none                   extsz=4096   blocks=0, rtextents=0
data blocks changed from 13107200 to 20318208
everything seemed to be fine, but then my home partition died. After reboot, I get into centos rescue mode and per my check, home partition couldn't be mounted.

Tried to repair using command below in rescue mode:
Code:
xfs_repair /dev/mapper/centos_sfvm03-home
but it can't find secondary super block.


unfortunately I don't have any backup and my data is important

Same problem on another threat is as below:

http://www.linuxquestions.org/questions/linux-newbie-8/after-lvreduce-reboot-now-can't-read-superblock-4175576100/

But I need more detailed guide for my case. This is a Virtual Machine and I have access to virtualization environment so I can increase hard disk over VMWare ESXi. Does it harm hard disk? as far as I read over the similar threat, I should increase reduced LV, can someone help me more detail on how to do that?
 
Old 11-11-2016, 08:15 AM   #2
BW-userx
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do you use UUID's in fstab (most Sys do now) ? they made may have been changed do to you changing its size. it is worth checking.
 
Old 11-11-2016, 08:20 AM   #3
sahruk
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Quote:
Originally Posted by BW-userx View Post
do you use UUID's in fstab (most Sys do now) ? they made may have been changed do to you changing its size. it is worth checking.
how if I say I don't have any idea about what you said? would you please tell it in detail?
As far as I know, one of sda sdb is XFS and another is Logical Volume
 
Old 11-11-2016, 08:30 AM   #4
Emerson
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Quote:
Originally Posted by man lvreduce
lvreduce allows you to reduce the size of a logical volume. Be careful when reducing a logical volume's size, because data in the reduced part is lost!!!
You should therefore ensure that any filesystem on the volume is resized before running lvreduce so that the extents that are to be removed are not in use.
You may have a slim chance to have something back if you undo both actions with lvreduce/lvextend.

Hard drives can die any time. Not having backups is asking for data loss.

Last edited by Emerson; 11-11-2016 at 08:31 AM.
 
Old 11-11-2016, 08:32 AM   #5
goumba
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Quote:
Originally Posted by sahruk View Post
unfortunately I don't have any backup and my data is important
Code:
  WARNING: Reducing active and open logical volume to 70.00 GiB
  THIS MAY DESTROY YOUR DATA (filesystem etc.)
Was a hint: do not do this if you care about your data and haven't made a backup.

That secondary superblock xfs_repair can't find was perhaps in the part of the FS that got chopped off when you resized.

Unfortunately that other thread you linked to holds your answer. There is no good way to resize an existing xfs filesystem, and you're likely going to have to get into some data recovery methods now to get that "important" data back. And the results of those methods are far from a guaranteed success.

Some further reading: http://blog.endpoint.com/2015/01/shr...-possible.html
 
Old 11-11-2016, 08:34 AM   #6
BW-userx
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Quote:
Originally Posted by sahruk View Post
how if I say I don't have any idea about what you said? would you please tell it in detail?
As far as I know, one of sda sdb is XFS and another is Logical Volume
Code:
blkid 

userx@SlackDaddy~>> sudo blkid
/dev/sda1: UUID="fa98942f-4219-4f0c-a9b1-0c3e2eda77e8" TYPE="ext4" PARTUUID="0f3f3740-01"
/dev/sda2: UUID="1bf3ce11-f34a-4e76-aab8-35d821739122" TYPE="ext4" PARTUUID="0f3f3740-02"
/dev/sda3: LABEL="ssdData" UUID="361c2abd-5393-4f12-af4d-6ef881f99a48" TYPE="ext4" PARTUUID="0f3f3740-03"
/dev/sdb1: LABEL="System Reserved" UUID="16BE1703BE16DAD7" TYPE="ntfs" PARTUUID="0004ed67-01"
/dev/sdb2: UUID="6602CF6F02CF42B3" TYPE="ntfs" PARTUUID="0004ed67-02"
/dev/sdb3: UUID="5550a765-506a-4ca6-aedc-b1c660dbb486" TYPE="ext4" PARTUUID="0004ed67-03"
/dev/sdb4: UUID="2cbaed98-039f-45d4-bf0d-4eb200009ec4" TYPE="ext4" PARTUUID="0004ed67-04"
/dev/sdc1: LABEL="WD3TB" UUID="89f35fb4-9578-42ca-9244-0f4b5ef1604d" TYPE="ext4"
in fstab, the UUIDs are put replacing the the old way, slack still uses the old way.
Code:
userx@SlackDaddy~>> cat /etc/fstab
/dev/sda1        /                ext4        defaults         1   1
/dev/sdb4        /home            ext4        defaults         1   2
#ssd data
/dev/sda3       /media/data       ext4        defaults         1   3 
/dev/sdb1        /media/windows10 ntfs-3g     fmask=111,dmask=000 1   0

#/dev/cdrom      /mnt/cdrom       auto        noauto,owner,ro,comment=x-gvfs-show 0   0
/dev/fd0         /mnt/floppy      auto        noauto,owner     0   0
devpts           /dev/pts         devpts      gid=5,mode=620   0   0
proc             /proc            proc        defaults         0   0
tmpfs            /dev/shm         tmpfs       defaults         0   0
an fstab that uses UUID's looks like this,

Code:
# /etc/fstab: static file system information.
#
# Use 'blkid' to print the universally unique identifier for a
# device; this may be used with UUID= as a more robust way to name devices
# that works even if disks are added and removed. See fstab(5).
#
# <file system> <mount point>   <type>  <options>       <dump>  <pass>
# / was on /dev/sdb3 during installation
UUID=5550a765-506a-4ca6-aedc-b1c660dbb486 /               ext4    errors=remount-ro 0       1
# /home was on /dev/sdb4 during installation
UUID=2cbaed98-039f-45d4-bf0d-4eb200009ec4 /home           ext4    defaults        0       2
if your fstab uses UUID's they may have changed on your partitions due to the change you made. a quick cat to your fstab and blkid in your terminal will give you ca quick look to see if that is a true statement or not. Thus eliminating that possibility if it is a false. If true then change them in your fstab to reflect the new UUID's.
 
Old 11-11-2016, 08:35 AM   #7
sahruk
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Quote:
Originally Posted by Emerson View Post
You may have a slim chance to have something back if you undo both actions with lvreduce/lvextend.

Hard drives can die any time. Not having backups is asking for data loss.
Yes I see that my chance is slim in this way, but even so, what exactly I should do?
I decreased home and increased root as you can see in first post.(whole disk was 150GB) Now I have chance to change hard disk from 150GB to 200GB over VMWare. Is it better to do so without doing exactly reverse by just increasing home again? and if yes, how shall I do it, what commands do I need I mean?
 
Old 11-11-2016, 08:38 AM   #8
BW-userx
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Quote:
Originally Posted by sahruk View Post
Yes I see that my chance is slim in this way, but even so, what exactly I should do?
I decreased home and increased root as you can see in first post.(whole disk was 150GB) Now I have chance to change hard disk from 150GB to 200GB over VMWare. Is it better to do so without doing exactly reverse by just increasing home again? and if yes, how shall I do it, what commands do I need I mean?
I don't know the commands but the restore should be part of it and not resize to put that back.
 
Old 11-11-2016, 08:46 AM   #9
sahruk
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Quote:
Originally Posted by goumba View Post
Code:
  WARNING: Reducing active and open logical volume to 70.00 GiB
  THIS MAY DESTROY YOUR DATA (filesystem etc.)
Was a hint: do not do this if you care about your data and haven't made a backup.

That secondary superblock xfs_repair can't find was perhaps in the part of the FS that got chopped off when you resized.

Unfortunately that other thread you linked to holds your answer. There is no good way to resize an existing xfs filesystem, and you're likely going to have to get into some data recovery methods now to get that "important" data back. And the results of those methods are far from a guaranteed success.

Some further reading: http://blog.endpoint.com/2015/01/shr...-possible.html

Yes, I understand what stupid thing I did. I'm just duplicating my virtual disk of Virtual machine to have chance on my tests I will go on. So the link you shared is about what I could do before I did this horrible thing, right?
 
Old 11-11-2016, 08:52 AM   #10
goumba
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Quote:
Originally Posted by sahruk View Post
Yes, I understand what stupid thing I did. I'm just duplicating my virtual disk of Virtual machine to have chance on my tests I will go on. So the link you shared is about what I could do before I did this horrible thing, right?
Yes. And next time around, if you think you will ever need to resize that volume, consider using a filesystem that can be resized.

As Emerson suggested, undo the resize, assuming no data had been written, and the repair attempt did not make things worse - this may give you a chance at getting your data back.

However, be warned, you have to put things EXACTLY as they were. The same number of extents, and everything has to be exactly where it was. Same starting sector, same starting extent, same ending extent, etc.
 
Old 11-11-2016, 08:59 AM   #11
sahruk
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Quote:
Originally Posted by goumba View Post
Yes. And next time around, if you think you will ever need to resize that volume, consider using a filesystem that can be resized.

As Emerson suggested, undo the resize, assuming no data had been written, and the repair attempt did not make things worse - this may give you a chance at getting your data back.

However, be warned, you have to put things EXACTLY as they were. The same number of extents, and everything has to be exactly where it was. Same starting sector, same starting extent, same ending extent, etc.
As far as I'm not a pro linux user, I thing I need to get some pro's hand on this issue.
 
Old 11-11-2016, 09:24 AM   #12
BW-userx
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Quote:
Originally Posted by sahruk View Post
As far as I'm not a pro linux user, I thing I need to get some pro's hand on this issue.
Quote:
XFS can handle file systems of up to 18 exabytes, with a maximum file size of 9 exabytes. There is no limit on the number of files.
are you even dealing with HARD DRIVES this big? seems over kill to me to even have such a file system if not. MOOC

Quote:
In 2009, version 5.4 of 64-bit Red Hat Enterprise Linux (RHEL) Linux distribution contained the necessary kernel support for the creation and usage of XFS file systems, but lacked the corresponding command-line tools. The tools available from CentOS could operate for that purpose, and they were previously also provided[by whom?] to RHEL customers on request.[13] RHEL 6.0, released in 2010, includes XFS support for a fee as part of Red Hat's "scalable file system add-on".[14] Oracle Linux 6, released in 2011, also includes an option for using XFS.[15]

RHEL 7.0, released in June 2014, uses XFS as its default file system, including support for using XFS for the /boot partition.[16]

Linux 4.8 added a new large feature, "reverse mapping". The foundation of a set of new features as snapshots, copy-on-write (COW) data, data deduplication, online data and metadata scrubbing, highly accurate bad sector/data loss reporting and significantly improved reconstruction of damaged or corrupted filesystems.[17]
go to the source would be my suggestion

Last edited by BW-userx; 11-11-2016 at 09:40 AM.
 
Old 11-11-2016, 09:32 AM   #13
sahruk
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Quote:
Originally Posted by BW-userx View Post
are you even dealing with HARD DRIVES this big? seems over kill to me to even have such a file system if not. MOOC
Nope, The server we are talking about is just a simple CPanel/WHM Centos 7 running OS server hosting 200-300 websites. Strictly I'm not sure why this type of partition chosen (default suggested or whatever) but I'm just managing the server, not the first creator.

I will try with doing reverse tasks to see if I can have my home partition back or not, if not I will go with data recovery steps (I don't have any idea about this on linux, I should read more) to recover home directory and MySQL data storage which are critical for me to have them back.
 
Old 11-11-2016, 09:45 AM   #14
BW-userx
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Quote:
Originally Posted by sahruk View Post
Nope, The server we are talking about is just a simple CPanel/WHM Centos 7 running OS server hosting 200-300 websites. Strictly I'm not sure why this type of partition chosen (default suggested or whatever) but I'm just managing the server, not the first creator.

I will try with doing reverse tasks to see if I can have my home partition back or not, if not I will go with data recovery steps (I don't have any idea about this on linux, I should read more) to recover home directory and MySQL data storage which are critical for me to have them back.
ah oh boy are you in trouble not your toys to play with? I moded my post, wiki said something about the 4.8 kernel having reverse mapping and red hat / Centos having tools to deal with your file system. GO red hat ... !!! woop woop woop !!! good luck ...
 
Old 11-11-2016, 09:48 AM   #15
BW-userx
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some googled links that might help

key words restore xfs partition

http://www.reclaime.com/library/xfs-recovery.aspx


http://serverfault.com/questions/469...ck-read-failed

http://docs.cray.com/books/S-2377-22...bhdyq9i26.html
 
  


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