Increase the size of the /dev/mapper/centos_centos7-root

By | October 10, 2019

From our monitoring we received a disk full alert for our configuration backup server, which is a CentOS VM.

Nagios XI Alert
This is an escalated notification
Type: PROBLEM
Servicecheck:/ Disk Usage
Hostname: *CentOS_Server*
State: WARNING
service_output:
/: 95%used(25740MB/27091MB) (95%) : WARNING
service_long_output:

So we needed to increase the size of this volume. In our case the volume /dev/mapper/centos_centos7-root was on a physical disk with that has a total capacity of 60GB. A mere 26Gb was in use so there was more then 30GB of free space to be allocated:

The file system sits on top while the physical disk is the first tier if you will.
4. File system
3. Logical Volumes
2. Logical Volume group
1. Physical disk

[root@conf ~]# df -h
Filesystem                           Size  Used Avail Use% Mounted on
/dev/mapper/centos_centos7-root       27G   26G  1.4G  96% /
devtmpfs                             475M     0  475M   0% /dev
tmpfs                                487M     0  487M   0% /dev/shm
tmpfs                                487M   51M  437M  11% /run
tmpfs                                487M     0  487M   0% /sys/fs/cgroup
/dev/mapper/VolGroup01-VCSA--Backup  250G   18G  233G   8% /mnt/VCSA-Backup
/dev/sda1                            497M  229M  268M  47% /boot
tmpfs                                 98M     0   98M   0% /run/user/0
[root@conf ~]# lvs
  LV          VG             Attr       LSize    Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
  VCSA-Backup VolGroup01     -wi-ao---- <250.00g
  root        centos_centos7 -wi-ao----  <26.47g
  swap        centos_centos7 -wi-ao----    3.00g
[root@confbackup ~]# fdisk -l

Disk /dev/sda: 64.4 GB, 64424509440 bytes, 125829120 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: 0x000a5cdd

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *        2048     1026047      512000   83  Linux
/dev/sda2         1026048    62914559    30944256   8e  Linux LVM

Disk /dev/sdb: 268.4 GB, 268435456000 bytes, 524288000 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: 0x00000000

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1              63   524287999   262143968+  8e  Linux LVM

Disk /dev/mapper/centos_centos7-swap: 3221 MB, 3221225472 bytes, 6291456 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/centos_centos7-root: 28.4 GB, 28420603904 bytes, 55508992 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/VolGroup01-VCSA--Backup: 268.4 GB, 268431261696 bytes, 524279808 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

volume group display (vgdisplay) to see the size of the volume groups

[root@confbackup ~]# vgdisplay
  --- Volume group ---
  VG Name               VolGroup01
  System ID
  Format                lvm2
  Metadata Areas        1
  Metadata Sequence No  2
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                1
  Open LV               1
  Max PV                0
  Cur PV                1
  Act PV                1
  VG Size               <250.00 GiB
  PE Size               4.00 MiB
  Total PE              63999
  Alloc PE / Size       63999 / <250.00 GiB
  Free  PE / Size       0 / 0

  --- Volume group ---
  VG Name               centos_centos7
  System ID
  Format                lvm2
  Metadata Areas        1
  Metadata Sequence No  3
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                2
  Open LV               2
  Max PV                0
  Cur PV                1
  Act PV                1
  VG Size               <29.51 GiB
  PE Size               4.00 MiB
  Total PE              7554
  Alloc PE / Size       7544 / <29.47 GiB
  Free  PE / Size       10 / 40.00 MiB

Do a lvdisplay to list the size of the logical volumes, important is the root partition. You can see that the size is a mere 26GB (other lv’s on the list is filtered out)

[root@confbackup ~]# lvdisplay 
--- Logical volume ---
  LV Path                /dev/centos_centos7/root
  LV Name                root
  VG Name                centos_centos7
  LV Write Access        read/write
  LV Creation host, time localhost.localdomain, 2015-04-08 18:19:04 +0200
  LV Status              available
  # open                 1
  LV Size                <26.47 GiB
  Current LE             6776
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     8192
  Block device           253:1

Do a pvdisplay to list the size of the physical volume, in our case /dev/sda2 needs te be extended

[root@confbackup ~]# pvdisplay
  --- Physical volume ---
  PV Name               /dev/sdb1
  VG Name               VolGroup01
  PV Size               <250.00 GiB / not usable <3.97 MiB
  Allocatable           yes (but full)
  PE Size               4.00 MiB
  Total PE              63999
  Free PE               0
  Allocated PE          63999

  --- Physical volume ---
  PV Name               /dev/sda2
  VG Name               centos_centos7
  PV Size               29.51 GiB / not usable 3.00 MiB
  Allocatable           yes
  PE Size               4.00 MiB
  Total PE              7554
  Free PE               10
  Allocated PE          7544

Extend the partition

[root@confbackup ~]# 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): 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): p

Disk /dev/sda: 64.4 GB, 64424509440 bytes, 125829120 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: 0x000a5cdd

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *        2048     1026047      512000   83  Linux
/dev/sda2         1026048    62914559    30944256   8e  Linux LVM

Command (m for help): n
Partition type:
   p   primary (2 primary, 0 extended, 2 free)
   e   extended
Select (default p): p
Partition number (3,4, default 3):
First sector (62914560-125829119, default 62914560):
Using default value 62914560
Last sector, +sectors or +size{K,M,G} (62914560-125829119, default 125829119):
Using default value 125829119
Partition 3 of type Linux and of size 30 GiB is set

Command (m for help): p

Disk /dev/sda: 64.4 GB, 64424509440 bytes, 125829120 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: 0x000a5cdd

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *        2048     1026047      512000   83  Linux
/dev/sda2         1026048    62914559    30944256   8e  Linux LVM
/dev/sda3        62914560   125829119    31457280   83  Linux

Command (m for help): t
Partition number (1-3, default 3):
Hex code (type L to list all codes): 8e
Changed type of partition 'Linux' to 'Linux LVM'

Command (m for help): p

Disk /dev/sda: 64.4 GB, 64424509440 bytes, 125829120 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: 0x000a5cdd

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *        2048     1026047      512000   83  Linux
/dev/sda2         1026048    62914559    30944256   8e  Linux LVM
/dev/sda3        62914560   125829119    31457280   8e  Linux LVM

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.
[root@confbackup ~]# partprobe
[root@confbackup ~]# ls -l
total 0
[root@confbackup ~]# ls -l /dev/sd*
brw-rw----. 1 root disk 8,  0 Oct 10 12:24 /dev/sda
brw-rw----. 1 root disk 8,  1 Oct 10 12:24 /dev/sda1
brw-rw----. 1 root disk 8,  2 Oct 10 12:24 /dev/sda2
brw-rw----. 1 root disk 8,  3 Oct 10 12:24 /dev/sda3
brw-rw----. 1 root disk 8, 16 Oct 10 12:24 /dev/sdb
brw-rw----. 1 root disk 8, 17 Oct 10 12:24 /dev/sdb1
[root@confbackup ~]# pvcreate /dev/sda3
  Physical volume "/dev/sda3" successfully created.
[root@confbackup ~]# vgdisplay
  --- Volume group ---
  VG Name               VolGroup01
  System ID
  Format                lvm2
  Metadata Areas        1
  Metadata Sequence No  2
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                1
  Open LV               1
  Max PV                0
  Cur PV                1
  Act PV                1
  VG Size               <250.00 GiB
  PE Size               4.00 MiB
  Total PE              63999
  Alloc PE / Size       63999 / <250.00 GiB
  Free  PE / Size       0 / 0
  VG UUID               IN49ef-10HQ-5i4K-nvzA-zpzW-xn5U-ohesf0

  --- Volume group ---
  VG Name               centos_centos7
  System ID
  Format                lvm2
  Metadata Areas        1
  Metadata Sequence No  3
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                2
  Open LV               2
  Max PV                0
  Cur PV                1
  Act PV                1
  VG Size               <29.51 GiB
  PE Size               4.00 MiB
  Total PE              7554
  Alloc PE / Size       7544 / <29.47 GiB
  Free  PE / Size       10 / 40.00 MiB
  VG UUID               Mlwe8D-BeAr-wV8v-e332-vXpX-LmdD-DBsvWo

[root@confbackup ~]# vgextend centos_centos7 /dev/sda3
  Volume group "centos_centos7" successfully extended
[root@confbackup ~]# vgdisplay
  --- Volume group ---
  VG Name               VolGroup01
  System ID
  Format                lvm2
  Metadata Areas        1
  Metadata Sequence No  2
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                1
  Open LV               1
  Max PV                0
  Cur PV                1
  Act PV                1
  VG Size               <250.00 GiB
  PE Size               4.00 MiB
  Total PE              63999
  Alloc PE / Size       63999 / <250.00 GiB
  Free  PE / Size       0 / 0
  VG UUID               IN49ef-10HQ-5i4K-nvzA-zpzW-xn5U-ohesf0

  --- Volume group ---
  VG Name               centos_centos7
  System ID
  Format                lvm2
  Metadata Areas        2
  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                2
  Act PV                2
  VG Size               59.50 GiB
  PE Size               4.00 MiB
  Total PE              15233
  Alloc PE / Size       7544 / <29.47 GiB
  Free  PE / Size       7689 / <30.04 GiB
  VG UUID               Mlwe8D-BeAr-wV8v-e332-vXpX-LmdD-DBsvWo

Now extend the volume with 10GB

[root@confbackup ~]# lvextend /dev/centos_centos7/root -L +10G
  Size of logical volume centos_centos7/root changed from <26.47 GiB (6776 
  extents) to <36.47 GiB (9336 extents).
  Logical volume centos_centos7/root successfully resized.

Resize the file system

[root@confbackup ~]# resize2fs /dev/centos_centos7/root
resize2fs 1.42.9 (28-Dec-2013)
resize2fs: Bad magic number in super-block while trying to open /dev/centos_centos7/root
Couldn't find valid filesystem superblock.
[root@confbackup ~]# mount
sysfs on /sys type sysfs (rw,nosuid,nodev,noexec,relatime,seclabel)
proc on /proc type proc (rw,nosuid,nodev,noexec,relatime)
[root@confbackup ~]# xfs_growfs /
meta-data=/dev/mapper/centos_centos7-root isize=256    agcount=4, agsize=1734656 blks
         =                       sectsz=512   attr=2, projid32bit=1
         =                       crc=0        finobt=0 spinodes=0
data     =                       bsize=4096   blocks=6938624, imaxpct=25
         =                       sunit=0      swidth=0 blks
naming   =version 2              bsize=4096   ascii-ci=0 ftype=0
log      =internal               bsize=4096   blocks=3388, version=2
         =                       sectsz=512   sunit=0 blks, lazy-count=1
realtime =none                   extsz=4096   blocks=0, rtextents=0
data blocks changed from 6938624 to 9560064

/dev/mapper/centos_centos7-root is increased with 10GB to 37GB

[root@confbackup ~]# df -h
Filesystem                           Size  Used Avail Use% Mounted on
/dev/mapper/centos_centos7-root       37G   26G   12G  69% /
devtmpfs                             475M     0  475M   0% /dev
tmpfs                                487M     0  487M   0% /dev/shm
tmpfs                                487M   51M  437M  11% /run
tmpfs                                487M     0  487M   0% /sys/fs/cgroup
/dev/mapper/VolGroup01-VCSA--Backup  250G   18G  233G   8% /mnt/VCSA-Backup
/dev/sda1                            497M  229M  268M  47% /boot
tmpfs                                 98M     0   98M   0% /run/user/0

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