CephNotes

Some notes about Ceph
Laurent Barbe @CCM Benchmark

Map Rbd Kernel Without Install Ceph-common

It is not mandatory to install Ceph binaries (especially ceph-common) to be able to map a Rbd blocdevice you can also use the kernel path /sys/bus/rbd provided by rbd module.

$ modprobe rbd
$ echo "192.168.0.1,192.168.0.2,192.168.0.3 name=admin,secret=AQBG5SlSmLELKBAA6sKvuJyRWUmFl2R5E1ukTw== rbd testrbd" > /sys/bus/rbd/add

Startup rc script

For map rbd on startup and unmap on shutdown you can use this modified rc script http://cephnotes.ksperis.com/downloads/rbdmap

You do not need ceph-common :

$  apt-cache policy ceph-common
ceph-common:
  Installed: (none)
  Candidate: 0.67.4-0ubuntu2
  Version table:
     0.67.4-0ubuntu2 0
        500 http://fr.archive.ubuntu.com/ubuntu/ saucy/main amd64 Packages

You need to have a ceph.conf file with mon_host var :

$ egrep 'mon[ _]host' /etc/ceph/ceph.conf
mon_host = 192.168.0.1,192.168.0.2,192.168.0.3

And /etc/ceph/rbdmap file with this format :

$ cat /etc/ceph/rbdmap
rbd/testrbd id=admin,secret=AQBG5SlSmLELKBAA6sKvuJyRWUmFl2R5E1ukTw==

Be carefull tu use “id=” and “secret=” (not user, key or keyfile…) Then, download this modify rc script :

$ wget http://cephnotes.ksperis.com/downloads/rbdmap -O /etc/init.d/rbdmap
$ chmod +x /etc/init.d/rbdmap
$ update-rc.d rbdmap defaults

Test :

$ /etc/init.d/rbdmap start
* Starting RBD Mapping             [ OK ]
* Mounting all filesystems...      [ OK ]

$ ls /dev/rbd/*
testrbd

$ /etc/init.d/rbdmap stop
* Stopping RBD Mapping             [ OK ]

$ ls /dev/rbd/*
ls: cannot access /dev/rbd/*: No such file or directory

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