Saturday 28 March 2020

Bad magic number in super-block while trying to open /dev/rhel/root

While running an oracle upgrade i ran into file system space issues, in Rhel 7 without any downtime, how we can extend the volumes please check here, There are some steps that we have to follow :

1. Present a new physical disk to the server

2. Adding the new physical disk to an exisiting Volume Group.

3. Expanding a logical volume within that Volume Group to use the new disk space.

4. Notify the operating system about the change in size.

[oracle@rhel7 ~]$ su -
Password:
Last login: Sat Mar 28 21:11:53 IST 2020 on pts/3
[root@rhel7 ~]# fdisk -l

Disk /dev/sda: 128.8 GB, 128849018880 bytes, 251658240 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0x000b49f1

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *        2048     2050047     1024000   83  Linux
/dev/sda2         2050048   100370431    49160192   8e  Linux LVM

Disk /dev/mapper/rhel-root: 41.9 GB, 41943040000 bytes, 81920000 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes


Disk /dev/mapper/rhel-swap: 8388 MB, 8388608000 bytes, 16384000 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes

Step 1: Present the new physical disk to the server.

And Step 2: Add the new physical disk to an existing Volume Group.

[root@rhel7 ~]# fdisk /dev/sda
Welcome to fdisk (util-linux 2.23.2).

Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.


Command (m for help): n
Partition type:
   p   primary (2 primary, 0 extended, 2 free)
   e   extended
Select (default p): e
Partition number (3,4, default 3):
First sector (100370432-251658239, default 100370432):
Using default value 100370432
Last sector, +sectors or +size{K,M,G} (100370432-251658239, default 251658239): +40G
Partition 3 of type Extended and of size 40 GiB is set

Command (m for help): m
Command action
   a   toggle a bootable flag
   b   edit bsd disklabel
   c   toggle the dos compatibility flag
   d   delete a partition
   g   create a new empty GPT partition table
   G   create an IRIX (SGI) partition table
   l   list known partition types
   m   print this menu
   n   add a new partition
   o   create a new empty DOS partition table
   p   print the partition table
   q   quit without saving changes
   s   create a new empty Sun disklabel
   t   change a partition's system id
   u   change display/entry units
   v   verify the partition table
   w   write table to disk and exit
   x   extra functionality (experts only)

Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.

WARNING: Re-reading the partition table failed with error 16: Device or resource busy.
The kernel still uses the old table. The new table will be used at
the next reboot or after you run partprobe(8) or kpartx(8)
Syncing disks.

# Now run the partprobe command to sync the changes

[root@rhel7 ~]# partprobe
[root@rhel7 ~]# fdisk -l

Disk /dev/sda: 128.8 GB, 128849018880 bytes, 251658240 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0x000b49f1

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *        2048     2050047     1024000   83  Linux
/dev/sda2         2050048   100370431    49160192   8e  Linux LVM
/dev/sda3       100370432   184256511    41943040    5  Extended

Disk /dev/mapper/rhel-root: 41.9 GB, 41943040000 bytes, 81920000 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes


Disk /dev/mapper/rhel-swap: 8388 MB, 8388608000 bytes, 16384000 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes


[root@rhel7 ~]# vgdisplay
  --- Volume group ---
  VG Name               rhel
  System ID           
  Format                lvm2
  Metadata Areas        3
  Metadata Sequence No  5
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                2
  Open LV               2
  Max PV                0
  Cur PV                3
  Act PV                3
  VG Size               86.87 GiB
  PE Size               4.00 MiB
  Total PE              22239
  Alloc PE / Size       12000 / 46.88 GiB
  Free  PE / Size       10239 / 40.00 GiB
  VG UUID               NvVNw2-XR30-7oS3-eGkz-81ZP-YziW-G238Kw

Step 3: Expand the logical volume to use the new space
 
[root@rhel7 ~]# lvdisplay
  --- Logical volume ---
  LV Path                /dev/rhel/root
  LV Name                root
  VG Name                rhel
  LV UUID                QibbKI-Hu0u-5I16-nYhe-VRXI-a14N-JgyX8N
  LV Write Access        read/write
  LV Creation host, time localhost, 2020-03-28 20:23:37 +0530
  LV Status              available
  # open                 1
  LV Size                39.06 GiB
  Current LE             10000
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     8192
  Block device           253:0
 
  --- Logical volume ---
  LV Path                /dev/rhel/swap
  LV Name                swap
  VG Name                rhel
  LV UUID                ATHN2H-ycQ6-Z0az-pkxp-jCvF-2JBd-OWs7KG
  LV Write Access        read/write
  LV Creation host, time localhost, 2020-03-28 20:23:37 +0530
  LV Status              available
  # open                 2
  LV Size                7.81 GiB
  Current LE             2000
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     8192
  Block device           253:1
 
[root@rhel7 ~]# lvextend -L+30G /dev/rhel/root
  Extending logical volume root to 69.06 GiB
  Logical volume root successfully resized


[root@rhel7 ~]# lvextend -L+8G /dev/rhel/root
  Extending logical volume root to 77.06 GiB
  Logical volume root successfully resized

# I ran into an issue with below command, the fix for that is given below,
# this is step 4 Step 4: Update the filesystem to use the new space

[root@rhel7 ~]# resize2fs /dev/rhel/root
resize2fs 1.42.9 (28-Dec-2013)
resize2fs: Bad magic number in super-block while trying to open /dev/rhel/root
Couldn't find valid filesystem superblock.

Check the space is still low :

[root@rhel7 ~]# df -h
Filesystem             Size  Used Avail Use% Mounted on
/dev/mapper/rhel-root   40G   37G  2.4G  95% /
devtmpfs               6.0G     0  6.0G   0% /dev
tmpfs                  6.0G  148K  6.0G   1% /dev/shm
tmpfs                  6.0G  8.9M  6.0G   1% /run
tmpfs                  6.0G     0  6.0G   0% /sys/fs/cgroup
/dev/sda1              997M  126M  872M  13% /boot



[root@rhel7 ~]# xfs_growfs /dev/rhel/root
meta-data=/dev/mapper/rhel-root  isize=256    agcount=4, agsize=2560000 blks
         =                       sectsz=512   attr=2, projid32bit=1
         =                       crc=0
data     =                       bsize=4096   blocks=10240000, imaxpct=25
         =                       sunit=0      swidth=0 blks
naming   =version 2              bsize=4096   ascii-ci=0 ftype=0
log      =internal               bsize=4096   blocks=5000, version=2
         =                       sectsz=512   sunit=0 blks, lazy-count=1
realtime =none                   extsz=4096   blocks=0, rtextents=0
data blocks changed from 10240000 to 20201472


# Now check the space, its 78 GB now

[root@rhel7 ~]# df -h
Filesystem             Size  Used Avail Use% Mounted on
/dev/mapper/rhel-root   78G   37G   41G  48% /
devtmpfs               6.0G     0  6.0G   0% /dev
tmpfs                  6.0G  148K  6.0G   1% /dev/shm
tmpfs                  6.0G  8.9M  6.0G   1% /run
tmpfs                  6.0G     0  6.0G   0% /sys/fs/cgroup
/dev/sda1              997M  126M  872M  13% /boot


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