Kushal Das4

FOSS and life. Kushal Das talks here.

How to mount a raw guest image?

While testing the latest Fedora 24 cloud images, I had to mount it locally so that I inspect the files inside. We can do this by using the offset value calculated from the fdisk command.

# fdisk -l /var/lib/imagefactory/storage/7c34e40b-b27c-4cd9-ae05-459c93c98005.body
Disk /var/lib/imagefactory/storage/7c34e40b-b27c-4cd9-ae05-459c93c98005.body: 3 GiB, 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
Disklabel type: dos
Disk identifier: 0xfeecffb4

Device                                                                   Boot Start     End Sectors Size Id Type
/var/lib/imagefactory/storage/7c34e40b-b27c-4cd9-ae05-459c93c98005.body1 *     2048 6291455 6289408   3G 83 Linux

In this case the start value is 2048, and each sector is 512 bytes, so our offset value is 2048 * 512 = 1048576.

# mount -o offset=1048576 /var/lib/imagefactory/storage/7c34e40b-b27c-4cd9-ae05-459c93c98005.body /mnt
[root@fedora-build f23]# ls /mnt/
bin  boot  dev  etc  home  lib  lib64  lost+found  media  mnt  opt  proc  root  run  sbin  srv  sys  tmp  usr  var

Home storage cluster with Fedora and Gluster

In a previous post I wrote about the encrypted storage I am using at home. Using Banana Pi, and Fedora. But, for my photos I had to look for something else. I need redundancy. The of the self NAS boxes which can do network and RAID are super costly in my standard.

So, I decided to build that at home. The setup is simple that can be done in few hours. I have 2 Banana Pi(s) running Gluster, replicated 2TB hard drives over a local Gigabit network. My old Banana Pi is where I mounted the Gluster volume.

First set up the Fedora for Banana Pi(s).

I am using the minimal Fedora 23 images.

$ sudo fedora-arm-image-installer --image=/home/kdas/Fedora-Minimal-armhfp-23-10-sda.raw.xz --target=Bananapi --media=/dev/mmcblk0 --selinux=ON

Due to a bug in the F23 images, I had to remove initial-setup service from the installations.

$ rm /run/media/kdas/__/etc/systemd/system/multi-user.target.wants/initial-setup-text.service

Then I setup my ssh key on the cards.

$ sudo mkdir /run/media/$USER/__/root/.ssh/
$ su -c 'cat /home/$USER/.ssh/id_rsa.pub >> /run/media/$USER/__/root/.ssh/authorized_keys'
$ sudo chmod -R u=rwX,o=,g= /run/media/$USER/__/root/.ssh/

Installing and enabling ntp

# dnf clean all
# dnf install ntp
# systemctl enable ntpd

Setting up the hostname

I just set the hostname on the all the 3 systems as gluster01, gluster02, and storage.

# hostnamectl set-hostname --static "gluster01"

Setting up static IP using networkd

I prefer to use Networkd on head less systems. So, I used the same to setup static network on all the systems.

# systemctl disable NetworkManager
# systemctl disable network
# systemctl enable systemd-networkd
# systemctl enable systemd-resolved
# systemctl start systemd-resolved
# systemctl start systemd-networkd
# rm -f /etc/resolv.conf
# ln -s /run/systemd/resolve/resolv.conf /etc/resolv.conf
# vi /etc/systemd/network/eth0.network

The configuration of the network file is given below. This is much easier for me to maintain than ifcfg files.

# These are optional but worth mentioning

Remember to setup all 3 systems in the similar way. Replace the IP/Gateway address as required. I also updated the /etc/hosts file in all the 3 systems so that they can talk to each other using hostname than IP addresses.

Setting up the new hard drives

First we create a new partition, and then format it as ext4. I also added the corresponding address in the fstab file so that it gets mounted automatically on /mnt.

# fdisk -c -u /dev/sda
# mkfs.ext4 /dev/sda1
# vim /etc/fstab

Setting up Gluster on the systems

Next big step is about setting up Gluster on both the gluster01 and on gluster02.

# dnf install glusterfs-server.armv7hl -y
# mkdir -p /mnt/brick/glusv0
# systemctl start glusterd

Next I had to enable the required ports in the firewalld. For now I have added eth0 on public zone.

# firewall-cmd --zone=public --add-interface=eth0
# firewall-cmd --zone=public --add-service=glusterfs

Remember to run the above commands on the both the Gluster systems. Now from gluster01 I enabled a peer. Finally we create the volume, and start it.

# gluster peer probe gluster02
# gluster peer status
# gluster volume create glusv0 replica 2 gluster01:/mnt/brick/glusv0 gluster02:/mnt/brick/glusv0
# gluster volume start glusv0
# gluster volume info

Mount the gluster volume on the third box.

# dnf install glusterfs-fuse -y
# mount -t glusterfs gluster01:/glusv0 /gluster -o backupvolfile-server=gluster02
# chown USERNAME -R /gluster/

Now you can use the mounted volume in any way you want. I also had a problem in keeping the systems properly. So, I used an old plastic rack to host the whole solution. Less than $5 in cost :)

Setting up storage for docker on Fedora22 cloud image

docker-storage-setup helps to create a LVM thin pool, which can be then used by docker for storage of containers, and images. By starting docker, it automatically starts this service. We can also make sure that it uses a specific block device, and volume group. In this example I am running Fedora 22 Cloud Base image on an Openstack environment, I added a new volume /dev/vdb to the instance.

# cat <<EOF > /etc/sysconfig/docker-storage-setup
# sudo docker-storage-setup
  Volume group "vda1" not found
  Cannot process volume group vda1
Checking that no-one is using this disk right now ... OK

Disk /dev/vdb: 5 GiB, 5379194880 bytes, 10506240 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
Disklabel type: dos
Disk identifier: 0xc8ed8872

Old situation:

>>> Script header accepted.
>>> Created a new DOS disklabel with disk identifier 0x39ca0d62.
Created a new partition 1 of type 'Linux LVM' and of size 5 GiB.
New situation:

Device     Boot Start      End  Sectors Size Id Type
/dev/vdb1        2048 10506239 10504192   5G 8e Linux LVM

The partition table has been altered.
Calling ioctl() to re-read partition table.
Syncing disks.
  Physical volume "/dev/vdb1" successfully created
  Volume group "docker-vg" successfully created
  Rounding up size to full physical extent 8.00 MiB
  Logical volume "docker-poolmeta" created.
  Logical volume "docker-pool" created.
  WARNING: Converting logical volume docker-vg/docker-pool and docker-vg/docker-poolmeta to pool's data and metadata volumes.
  Converted docker-vg/docker-pool to thin pool.
  Logical volume "docker-pool" changed

I hope this will help you to setup the docker storage properly on Fedora 22 Cloud Image.