Problem: Disk space on the Host machine is filling up.
- The total used disk space is @ 94%, disk space on the server need to be freed up
(prod)root@host:/var/lib/libvirt/images/maas-01.prod.setup# df -h
Filesystem Size Used Avail Use% Mounted on
udev 252G 39G 214G 16% /dev
tmpfs 51G 1.4M 51G 1% /run
/dev/dm-0 413G 367G 25G 94% /
none 4.0K 0 4.0K 0% /sys/fs/cgroup
none 5.0M 0 5.0M 0% /run/lock
none 252G 12K 252G 1% /run/shm
none 100M 0 100M 0% /run/user
/dev/sda1 237M 77M 148M 35% /bootAnalysis: The host machine has Multiple VM’s which are occupying large amount of disk space than the disk space actually used.
- List all the running VM’s
(prod)root@host:/var/lib/libvirt/images/maas-01.prod.setup# virsh list --all
Id Name State
----------------------------------------------------
2 oracle-01.prod.setup running
3 centos-01.prod.setup running
8 sql-01.prod.setup running
10 ntp-01.prod.setup running
11 config-01.prod.setup running
12 dns-01.prod.setup running
23 maas-01.prod.setup running- Using the disk usage command on /var/lib/libvirt/images, I was able to narrow down down on a VM disk image which was occupying substantial amount of disk space.
(prod)root@host:/var/lib/libvirt/images/maas-01.prod.setup# ls -lh
total 145G
-rw-r--r-- 1 root root 145G Sep 20 15:46 system.qcow2(prod)root@host:/var/lib/libvirt/images/maas-01.prod.setup# qemu-img info system.qcow2
image: system.qcow2
file format: qcow2
virtual size: 146G (157286400000 bytes)
disk size: 11G
cluster_size: 65536
Format specific information:
compat: 1.1
lazy refcounts: false- Actual disk utilization inside the VM is 2.4GB out of 145GB.
amold@maas-01:~$ df -h
Filesystem Size Used Avail Use% Mounted on
udev 3.9G 0 3.9G 0% /dev
tmpfs 799M 8.6M 790M 2% /run
/dev/vda1 145G 2.4G 136G 2% /
tmpfs 3.9G 12K 3.9G 1% /dev/shm
tmpfs 5.0M 0 5.0M 0% /run/lock
tmpfs 3.9G 0 3.9G 0% /sys/fs/cgroupSolution: Shrink the disk image to appropriate size on the Host machine and reclaim the free disk space.
- Mark the empty disk space in the guest VM - maas-01 by filling the free disk space with zero’s using multiple zero files.
dd if=/dev/zero of=zero-file bs=1M count=50000
dd if=/dev/zero of=zero-file2 bs=1M count=60000
dd if=/dev/zero of=zero-file2 bs=1M count=10000- Delete the zero files after creation
amold@maas-01:~$ rm -fv zero-file2 zero-file3 zero-file-
Logout of the VM & back to the KVM nodes
-
Shutdown the maas-01 VM
(prod)root@host: virsh stop maas-01.prod.setup- Rename the original disk image for the VM
(prod)root@host:/var/lib/libvirt/images/maas-01.prod.setup# mv system.qcow2 system.qcow2.original(prod)root@host:/var/lib/libvirt/images/maas-01.prod.setup# ls -lh
total 150G
-rw-r--r-- 1 root root 140G Sep 19 22:40 system.qcow2.original- Use qemu-img command to ceate a new disk image
(prod)root@host:/var/lib/libvirt/images/maas-01.prod.setup# qemu-img convert -O qcow2 system.qcow2.original system.qcow2(prod)root@host:/var/lib/libvirt/images/maas-01.prod.setup# ls -lh
total 150G
-rw-r--r-- 1 root root 11G Sep 20 15:46 system.qcow2
-rw-r--r-- 1 root root 140G Sep 19 22:40 system.qcow2.original(prod)root@host:/var/lib/libvirt/images/maas-01.prod.setup# qemu-img info system.qcow2
image: system.qcow2
file format: qcow2
virtual size: 146G (157286400000 bytes)
disk size: 11G
cluster_size: 65536
Format specific information:
compat: 1.1
lazy refcounts: falseThe new disk image is the resized/shrunk qcow2 file for the maas-01 VM. The new disk image has discarded all the zero disk data and considered the only the non zero bits.
- Start the maas-01 VM with the newly created disk image.
(prod)root@host: virsh start maas-01.prod.setup- Login to the maas-01 VM, the disk size reflected is as earlier.
amold@maas-01:~$ df -h
Filesystem Size Used Avail Use% Mounted on
udev 3.9G 0 3.9G 0% /dev
tmpfs 799M 8.6M 790M 2% /run
/dev/vda1 145G 2.3G 136G 2% /
tmpfs 3.9G 12K 3.9G 1% /dev/shm
tmpfs 5.0M 0 5.0M 0% /run/lock
tmpfs 3.9G 0 3.9G 0% /sys/fs/cgroupThis need to be resized as per actual disk usage.
- Shutdown the VM from host
(prod)root@host: virsh destroy maas-01.prod.setup- Use virt-df to view the VM’s disk filesystem details
(prod)root@host:/var/lib/libvirt/images/maas-01.prod.setup# virt-df system.qcow2
Filesystem 1K-blocks Used Available Use%
system.qcow2:/dev/sda1 1451481468 2405216 46935740 5%- Use guestfish to modify the guest VM’s filesystem.
This is an amazing tool to tweak the guest VM filesystem, to view - modify files, run commands, remove packages inside the disk image. It is advisible to shutdown the VM before trying any write operation to the disk image to avoid data corruption. More on guestfish @ http://libguestfs.org/guestfish.1.html
I am using the guestfish shell to perform disk resize for maas-01, same can be done using guestfish command.
(prod)root@host:/var/lib/libvirt/images/maas-01.prod.setup# guestfish -a system.qcow2
Welcome to guestfish, the guest filesystem shell for
editing virtual machine filesystems and disk images.
Type: 'help' for help on commands
'man' to read the manual
'quit' to quit the shell
><fs>run
><fs>e2fsck-f /dev/sda1
><fs>resize2fs-size /dev/sda1 20G
><fs>quit- Start the maas-01 VM
(prod)root@host: virsh start maas-01.prod.setup- View the resized disk changes inside the VM
amold@maas-01:~$ df -h
Filesystem Size Used Avail Use% Mounted on
udev 3.9G 0 3.9G 0% /dev
tmpfs 799M 8.6M 790M 2% /run
/dev/vda1 20G 2.3G 17G 13% /
tmpfs 3.9G 12K 3.9G 1% /dev/shm
tmpfs 5.0M 0 5.0M 0% /run/lock
tmpfs 3.9G 0 3.9G 0% /sys/fs/cgroupWhile working on resizing the disk image file, I though to reverse the process for expanding the disk image to increase the disk space to an adequate size in the VM.
- Shutdown the VM
(prod)root@host: virsh destroy maas-01.prod.setup- Use guestfish shell to execute resize2fs on the VM partition
(prod)root@host:/var/lib/libvirt/images/maas-01.prod.setup# guestfish -a system.qcow2
Welcome to guestfish, the guest filesystem shell for
editing virtual machine filesystems and disk images.
Type: 'help' for help on commands
'man' to read the manual
'quit' to quit the shell
><fs>run
><fs>e2fsck-f /dev/sda1
><fs>resize2fs-size /dev/sda1 50G
><fs>quit- Start VM & view the expanded partition
(prod)root@host: virsh start maas-01.prod.setup(prod)root@host:/var/lib/libvirt/images/maas-01.prod.setup# virt-df system.qcow2
Filesystem 1K-blocks Used Available Use%
system.qcow2:/dev/sda1 51481468 2405216 46935740 5%- SSH to the VM and verify the partition
amold@maas-01:~$ df -h
Filesystem Size Used Avail Use% Mounted on
udev 3.9G 0 3.9G 0% /dev
tmpfs 799M 8.6M 790M 2% /run
/dev/vda1 50G 2.3G 45G 5% /
tmpfs 3.9G 12K 3.9G 1% /dev/shm
tmpfs 5.0M 0 5.0M 0% /run/lock
tmpfs 3.9G 0 3.9G 0% /sys/fs/cgroup