20 01 2015
Update an OpenStack image
talset | glance, linux, openstack |
Quick presentation about 4 methodes (guestfish, guestmount, virt-* tools, qemu nbd) to update glance image. Add, remove, update files and install package before upload into glance.
Summary
- guestfish : Image is not mount directly on you file system. It provides you a shell with bases bash commandes (touch, edit, rm, chmod …)
- guestmount : Allows you to mount the image’s file system directly on your local file system
- virt-* tools : tools or modification directly in the image
- qemu nbd : mount filesystem without libguestfs
Examples
Get your image from glance
http://docs.openstack.org/image-guide/content/ch_modifying_images.html
List images into glance
glance image-list
+--------------------------------------+------------------------------------------------------------------+-------------+------------------+------------+--------+
| ID | Name | Disk Format | Container Format | Size | Status |
+--------------------------------------+------------------------------------------------------------------+-------------+------------------+------------+--------+
| 00d14bc2-7f43-4b3c-aed5-9cde8a694efb | CentOS 6.3 x86_64 final | qcow2 | bare | 755957760 | active |
glance image-list
Download your image
glance image-download 00d14bc2-7f43-4b3c-aed5-9cde8a694efb > CentOS.6.3.final.qcow2
guestfish
Run a virtual machin (don’t forget run)
guestfish --rw -a CentOS.6.3.final.qcow2
Welcome to guestfish, the libguestfs filesystem interactive shell for
editing virtual machine filesystems.
Type: 'help' for help on commands
'man' to read the manual
'quit' to quit the shell
><fs>
run
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Find and mount the logical volume root
<fs> list-filesystems
/dev/vda1: ext4
<fs> mount /dev/vda1 /
Make your changes
ls /etc/udev/rules.d/
60-raw.rules
70-persistent-cd.rules
70-persistent-net.rules
91-drm-modeset.rules
<fs> rm /etc/udev/rules.d/70-persistent-net.rules
Exit
guestmount
Package
apt-get install libguestfs-toolsbash
Mount/Umount glance image
guestmount -a CentOS.6.3.final.qcow2 -i --rw /mnt/
ls /mnt/
bin boot cgroup dev etc home lib lib64 lost+found media mnt opt proc root sbin selinux srv sys tmp usr var
Package install
To install packages like a running instance, you have to mount this
mount -t dev -o bind /dev /mnt/dev
mount --bind /dev/pts /mnt/dev/pts
mount -t proc -o bind /proc /mnt/proc
mount -t sys -o bind /sys /mnt/sys
Run chroot to enter into your image
Fix resolv.conf and do your stuff
echo 'nameserver 8.8.8.8' > /etc/resolv.conf
apt-get install
#or
yum install
#...
If you have not enough disk space, please refer to virt-resize section below
Clean your image
Manually
Clean
#Debian
apt-get autoremove
apt-get autoclean
apt-get clean
#Redhat
yum clean all
#tmp files
rm -rf /tmp/*
#user log
rm -f /var/log/wtmp /var/log/btmp
history -c
#... udev-persistent-net, .ssh ...
/sbin/shutdown -h now
Umount
umount /mnt/dev/pts
umount /mnt/dev
umount /mnt/proc
umount /mnt/sys
umount /mnt
Automatically
Or simply use virt-sysprep. This is a list of operation done by virt-sysprep
virt-sysprep --list-operations
bash-history * Remove the bash history in the guest
blkid-tab * Remove blkid tab in the guest
ca-certificates Remove CA certificates in the guest
cron-spool * Remove user at-jobs and cron-jobs
dhcp-client-state * Remove DHCP client leases
dhcp-server-state * Remove DHCP server leases
dovecot-data * Remove Dovecot (mail server) data
flag-reconfiguration Flag the system for reconfiguration
hostname * Change the hostname of the guest
kerberos-data Remove Kerberos data in the guest
logfiles * Remove many log files from the guest
mail-spool * Remove email from the local mail spool directory
net-hwaddr * Remove HWADDR (hard-coded MAC address) configuration
package-manager-cache * Remove package manager cache
pam-data * Remove the PAM data in the guest
random-seed * Generate random seed for guest
rhn-systemid * Remove the RHN system ID
samba-db-log * Remove the database and log files of Samba
script * Run arbitrary scripts against the guest
smolt-uuid * Remove the Smolt hardware UUID
ssh-hostkeys * Remove the SSH host keys in the guest
ssh-userdir * Remove ".ssh" directories in the guest
sssd-db-log * Remove the database and log files of sssd
udev-persistent-net * Remove udev persistent net rules
user-account Remove the user accounts in the guest
utmp * Remove the utmp file
yum-uuid * Remove the yum UUID
Umount to terminate your job
umount /mnt/dev/pts
umount /mnt/dev
umount /mnt/proc
umount /mnt/sys
umount /mnt
Clean
virt-sysprep -a CentOS.6.3.final.qcow2
Examining the guest ...
Performing "yum-uuid" ...
Performing "utmp" ...
Performing "udev-persistent-net" ...
Performing "sssd-db-log" ...
Performing "ssh-userdir" ...
Performing "ssh-hostkeys" ...
Performing "smolt-uuid" ...
Performing "script" ...
Performing "samba-db-log" ...
Performing "rhn-systemid" ...
Performing "random-seed" ...
Performing "pam-data" ...
Performing "package-manager-cache" ...
Performing "net-hwaddr" ...
Performing "mail-spool" ...
Performing "logfiles" ...
Performing "hostname" ...
Performing "dovecot-data" ...
Performing "dhcp-server-state" ...
Performing "dhcp-client-state" ...
Performing "cron-spool" ...
Performing "blkid-tab" ...
Performing "bash-history" ...
Finalisation
Converted back free space within the disk image to free space on the host
virt-sparsify --compress --tmp /tmp/ CentOS.6.3.final.qcow2 CentOS.6.3.final_2.0.qcow2
Create overlay file to protect source disk ...
Examine source disk ...
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Fill free space in /dev/vda1 with zero ...
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Copy to destination and make sparse ...
Sparsify operation completed with no errors. Before deleting the old
disk, carefully check that the target disk boots and works correctly.
Upload your new image version
glance --insecure image-create --name="CentOS 6.3 x86_64 final2.0" --disk-format=qcow2 --container-format=bare --file CentOS.6.3.final.qcow2
virt-* tools
A lot of tools are available :
- virt-edit for editing a file inside of an image.
- virt-df for displaying free space inside of an image.
- virt-resize for resizing an image.
- virt-sysprep for preparing an image for distribution (for example, delete SSH host keys, remove MAC address info, or remove user accounts).
- virt-sparsify for making an image sparse
- virt-p2v for converting a physical machine to an image that runs on KVM
- virt-v2v for converting Xen and VMware images to KVM images
Package installation
apt-get install libguestfs-tools
Example resize with virt-resize
Identify the root partitions
virt-filesystems --long --parts --blkdevs -h -a CentOS.6.3.final.qcow2
Name Type MBR Size Parent
/dev/sda1 partition 83 1022M /dev/sda
/dev/sda device - 1,0G -
Here we want resize /dev/sda1
Now create a new image with your needed size (Example : 2G)
qemu-img create -f qcow2 CentOS_6.3_x86_64_final-resized.qcow2 2G
Write a resized copy of the original into the new image
virt-resize --expand /dev/sda1 CentOS.6.3.final.qcow2 CentOS_6.3_x86_64_final-resized.qcow2
Examining CentOS.6.3.final.qcow2 ...
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**********
Summary of changes:
/dev/sda1: This partition will be resized from 1022,0M to 2,0G. The
filesystem ext4 on /dev/sda1 will be expanded using the 'resize2fs'
method.
**********
Setting up initial partition table on CentOS_6.3_x86_64_final-resized.qcow2 ...
Copying /dev/sda1 ...
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Expanding /dev/sda1 using the 'resize2fs' method ...
Resize operation completed with no errors. Before deleting the old
disk, carefully check that the resized disk boots and works correctly.
Done, you are able to use your resized image.
qemu nbd
requirement
apt-get install nbd-client qemu-utils
modprobe nbd max_part=63
Mount in RW with ndb
qemu-nbd -c /dev/nbd0 CentOS.6.3.final.qcow2
mount /dev/nbd0p1 /mnt/
Umount your image
umount /mnt/
nbd-client -d /dev/nbd0
Helpful links
glance, image, openstack, qcow2, update
