Mapping Ceph Block Device

Now that we have created a block device on a Ceph cluster, in order to use this block device, we need to map it to the client machine. To do this, execute the following commands from the client-node1 machine.

How to do it…

1. Map the block device to the client-node1:

   # rbd map --image rbd1 --name client.rbd
   

2. Check the mapped block device:

   # rbd showmapped --name client.rbd
   

   
3. To make use of this block device, we should create a filesystem on this and mount it:

   # fdisk -l /dev/rbd1
   # mkfs.xfs /dev/rbd1
   # mkdir /mnt/ceph-disk1
   # mount /dev/rbd1 /mnt/ceph-disk1
   # df -h /mnt/ceph-disk1

   
4. Test the block device by writing data to it:

   # dd if=/dev/zero of=/mnt/ceph-disk1/file1 count=100 bs=1M
   

   
5. To map the block device across reboots, you should add init-rbdmap script to the system startup, add the Ceph user and keyring details to /etc/ceph/rbdmap, and finally, update the /etc/fstab file:

   # wget https://raw.githubusercontent.com/ksingh7/ceph-cookbook/master/rbdmap -O /etc/init.d/rbdmap
   # chmod +x /etc/init.d/rbdmap
   # update-rc.d rbdmap defaults
   ## Make sure you use correct keyring value in /etc/ceph/rbdmap file, which is generally unique for an environment.
   # echo "rbd/rbd1 id=rbd,keyring=AQCLEg5VeAbGARAAE4ULXC7M5Fwd3BGFDiHRTw==" >> /etc/ceph/rbdmap
   # echo "/dev/rbd1 /mnt/ceph-disk1 xfs defaults, _netdev0 0 " >> /etc/fstab
   # mkdir /mnt/ceph-disk1
   # /etc/init.d/rbdmap start