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AndyM
Asked: 2018-01-20 14:40:05 +0800 CST

Cloud-growpart what am I doing wrong with partitioning

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I'm preparing a Centos7.4 cloud image and I have install cloud-init cloud-utils and cloud-growpart.

When I import into Openstack as a qcow2 image it doesn't resize my root if I create an instance with a bigger disk than the orginal image. If I use normal disks with no LVM and a single partition it works .

For some reason it doesnt like a 2 partition set up where /boot is partition1 and / is partition 2. All the docs seems to say that cloud-utils-growpart will work with lvm and ext4 if the root partition is the last partition. Any ideas ?

fstab

# /etc/fstab
# Created by anaconda on Fri Jan 19 16:49:58 2018
#
# Accessible filesystems, by reference, are maintained under '/dev/disk'
# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
# /dev/mapper/centos-root /                  ext4    defaults        1 1 UUID=aa806546-2582-411d-9eba-7217376a8aa3 /boot  ext3    defaults        1 2

and fdisk -l

[root@localhost ~]# fdisk -l

    Disk /dev/vda: 9234 MB, 9234180096 bytes, 18035508 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: 0x000b5cce

    Device Boot         Start         End      Blocks   Id  System
    /dev/vda1   *        2048      616447      307200   83  Linux
    /dev/vda2          616448    18034687     8709120   8e  Linux LVM

    Disk /dev/mapper/centos-root: 8917 MB, 8917090304 bytes, 17416192
    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
centos

1 Answers

  1. Best Answer

    I have the same problem - the reason is LVM. If you take a look at /var/log/cloud-init.log you will see entries like:

    cc_growpart.py[DEBUG]: '/' SKIPPED: device_part_info(/dev/mapper/centos_lxopce64v070-root) failed: /dev/mapper/centos_lxopce64v070-root not a partition

    So the answer is either to make your root partition a physical disk or to put in your own grow logic. I actually prefer to have my own logic as it makes expanding a root disk after the fact very easy without requiring an OpenStack resize (which requires rebuild of the VM). You simply attach a block volume, and then add the block volume to the LVM.

    So here is my code (very similar code if you are adding a block volume and growing the LVM). Your code probably differs only in the name of the root volume group (the_root_vgname):

    the_root_device='/dev/vda'
the_dynamic_partition='3'
the_dynamic_partition_path="${the_root_device}${the_dynamic_partition}"
the_root_vgname='centos_lxopce64v070'
the_root_lvname='root'
the_root_lvpath="/dev/${the_root_vgname}/${the_root_lvname}"
(echo n; echo p; echo $the_dynamic_partition; echo ; echo; echo t; echo $the_dynamic_partition; echo 8e; echo w) | fdisk ${the_root_device}
sync; sync; sync
partprobe
sync; sync; sync
pvcreate $the_dynamic_partition_path
sync; sync; sync
vgextend $the_root_vgname $the_dynamic_partition_path
sync; sync; sync
lvextend $the_root_lvpath $the_dynamic_partition_path
sync; sync; sync
xfs_growfs $the_root_lvpath
sync; sync; sync
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