How I extended disk size, volume group

My Spacewalk server which I run in the VirtualBox extended limit in root mount point. This is the situation right now:

[root@spacewalk ~]# df -h
Filesystem                         Size  Used Avail Use% Mounted on
/dev/mapper/centos_spacewalk-root   50G   50G   20K 100% /
devtmpfs                           913M     0  913M   0% /dev
tmpfs                              920M     0  920M   0% /dev/shm
tmpfs                              920M  8.3M  912M   1% /run
tmpfs                              920M     0  920M   0% /sys/fs/cgroup
/dev/mapper/centos_spacewalk-home  148G   33M  148G   1% /home
/dev/sda1                          497M   89M  409M  18% /boot
tmpfs                              184M     0  184M   0% /run/user/0

Now I powered off this machine and added new disk:

The new disk is 40GB big.

Once the system is booted I checked again if the disk is listed as device:

# fdisk -l | grep "^Disk /"
Disk /dev/sdb: 42.9 GB, 42949672960 bytes, 83886080 sectors
Disk /dev/sda: 214.7 GB, 214748364800 bytes, 419430400 sectors
Disk /dev/mapper/centos_spacewalk-root: 53.7 GB, 53687091200 bytes, 104857600 sectors
Disk /dev/mapper/centos_spacewalk-swap: 2147 MB, 2147483648 bytes, 4194304 sectors
Disk /dev/mapper/centos_spacewalk-home: 158.3 GB, 158318198784 bytes, 309215232 sectors

Yes! indeed there is new device /dev/sdb

Now it will get complicated. Lets check volume group situation. Mainly I need to look only above "Physical volumes" section:

# vgdisplay -v
    Using volume group(s) on command line.
  --- Volume group ---
  VG Name               centos_spacewalk
  System ID
  Format                lvm2
  Metadata Areas        1
  Metadata Sequence No  4
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                3
  Open LV               3
  Max PV                0
  Cur PV                1
  Act PV                1
  VG Size               199.51 GiB
  PE Size               4.00 MiB
  Total PE              51074
  Alloc PE / Size       51058 / 199.45 GiB
  Free  PE / Size       16 / 64.00 MiB
  VG UUID               nVGa5O-D3xL-b9au-vdy3-0Lvc-UHqd-BuulcE

  --- Logical volume ---
  LV Path                /dev/centos_spacewalk/swap
  LV Name                swap
  VG Name                centos_spacewalk
  LV UUID                llyVnR-J92n-4Ccu-QSnO-cWJt-HE0D-3cRyCB
  LV Write Access        read/write
  LV Creation host, time spacewalk.pro, 2016-09-29 11:46:42 -0400
  LV Status              available
  # open                 2
  LV Size                2.00 GiB
  Current LE             512
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     8192
  Block device           253:1

  --- Logical volume ---
  LV Path                /dev/centos_spacewalk/home
  LV Name                home
  VG Name                centos_spacewalk
  LV UUID                1YfWDN-gjDn-SFV1-NvCd-Yfj3-yXna-GKUMgI
  LV Write Access        read/write
  LV Creation host, time spacewalk.pro, 2016-09-29 11:46:42 -0400
  LV Status              available
  # open                 1
  LV Size                147.45 GiB
  Current LE             37746
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     8192
  Block device           253:2

  --- Logical volume ---
  LV Path                /dev/centos_spacewalk/root
  LV Name                root
  VG Name                centos_spacewalk
  LV UUID                MJVsOj-WB6q-RAP6-8iKI-LxPF-Ca6o-8PyQou
  LV Write Access        read/write
  LV Creation host, time spacewalk.pro, 2016-09-29 11:46:43 -0400
  LV Status              available
  # open                 1
  LV Size                50.00 GiB
  Current LE             12800
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     8192
  Block device           253:0

  --- Physical volumes ---
  PV Name               /dev/sda2
  PV UUID               syRcb1-52G9-epzE-gVJX-aN97-RRR0-Aw12vC
  PV Status             allocatable
  Total PE / Free PE    51074 / 16

I note down volume group base name which is this case is /dev/centos_spacewalk
Another thing is Free PE which means how much free space are unused. In very tight situations this can be 0 which means that every block is in production

Lets add the new disk to be managed by volume group. /dev/sdb do not need any partitions. This is weird and cool in same time :)

# vgextend /dev/centos_spacewalk /dev/sdb
  Physical volume "/dev/sdb" successfully created
  /etc/lvm/backup/centos_spacewalk.tmp: write error failed: No space left on device
  Backup of volume group centos_spacewalk metadata failed.
  Volume group "centos_spacewalk" successfully extended

I received "No space left on device" which looks like very bad.
Some success messages also appears.

I decided to clean some log files before I continue.
This will save something like 1 megabyte to operate in next commands:

> /var/log/cobbler/cobbler.log
> /var/log/messages

I have to work very quickly cause /var/log/messages are empty right now but it will fill full very quickly.

I run again vgdisplay -v to see that I have new blocks to use in environment :)

 --- Physical volumes ---
  PV Name               /dev/sda2
  PV UUID               syRcb1-52G9-epzE-gVJX-aN97-RRR0-Aw12vC
  PV Status             allocatable
  Total PE / Free PE    51074 / 16

  PV Name               /dev/sdb
  PV UUID               odzNaM-CBf4-PFpD-todW-sLoD-IDUP-dQrBNb
  PV Status             allocatable
  Total PE / Free PE    10239 / 10239

Lets give some unallocated space for /dev/centos_spacewalk/root which is the partition which desperately needs some free space:

lvextend /dev/centos_spacewalk/root /dev/sdb
  Size of logical volume centos_spacewalk/root changed from 50.00 GiB (12800 extents) to 90.00 GiB (23039 extents).
  Logical volume root successfully resized.

The final step is to let actual file system eat all the unallocated space:

resize2fs /dev/centos_spacewalk/root

resize2fs: Bad magic number in super-block while trying to open /dev/centos_spacewalk/root
Couldn't find valid filesystem superblock.

WTFloppy?

Turns out for xfs file system I need to use:

# xfs_growfs /dev/centos_spacewalk/root
meta-data=/dev/mapper/centos_spacewalk-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 23591936

Now I have successfully extended root mount point :)

# df -h
Filesystem                         Size  Used Avail Use% Mounted on
/dev/mapper/centos_spacewalk-root   90G   50G   40G  56% /
devtmpfs                           913M     0  913M   0% /dev
tmpfs                              920M     0  920M   0% /dev/shm
tmpfs                              920M  8.3M  912M   1% /run
tmpfs                              920M     0  920M   0% /sys/fs/cgroup
/dev/mapper/centos_spacewalk-home  148G   33M  148G   1% /home
/dev/sda1                          497M   89M  409M  18% /boot
tmpfs                              184M     0  184M   0% /run/user/0

echo "- - -" > /sys/class/scsi_host/host0/scan
echo "- - -" > /sys/class/scsi_host/host1/scan
echo "- - -" > /sys/class/scsi_host/host2/scan

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How I extended disk size, volume group