Return-Path: linux-nfs-owner@vger.kernel.org Received: from ducie-dc1.codethink.co.uk ([37.128.190.40]:60931 "EHLO ducie-dc1.codethink.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752706AbaAOR1R (ORCPT ); Wed, 15 Jan 2014 12:27:17 -0500 From: mark.doffman@codethink.co.uk To: ceph-devel@vger.kernel.org Cc: Rob Taylor , sage@inktank.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-nfs@vger.kernel.org, Mark Doffman Subject: [PATCH v2 2/2] Documentation: Document the cephroot functionality Date: Wed, 15 Jan 2014 11:26:29 -0600 Message-Id: <29b3bd9700e23df2aee095df8c34a15a62f57d27.1389806186.git.mark.doffman@codethink.co.uk> In-Reply-To: References: In-Reply-To: References: <1385000024-23463-1-git-send-email-mark.doffman@codethink.co.uk> Sender: linux-nfs-owner@vger.kernel.org List-ID: From: Rob Taylor Document using the cephfs as a root device, its purpose, functionality and use. Signed-off-by: Mark Doffman Signed-off-by: Rob Taylor Reviewed-by: Ian Molton --- Documentation/filesystems/{ => ceph}/ceph.txt | 0 Documentation/filesystems/ceph/cephroot.txt | 86 +++++++++++++++++++++++++++ 2 files changed, 86 insertions(+) rename Documentation/filesystems/{ => ceph}/ceph.txt (100%) create mode 100644 Documentation/filesystems/ceph/cephroot.txt diff --git a/Documentation/filesystems/ceph.txt b/Documentation/filesystems/ceph/ceph.txt similarity index 100% rename from Documentation/filesystems/ceph.txt rename to Documentation/filesystems/ceph/ceph.txt diff --git a/Documentation/filesystems/ceph/cephroot.txt b/Documentation/filesystems/ceph/cephroot.txt new file mode 100644 index 0000000..deda4f0 --- /dev/null +++ b/Documentation/filesystems/ceph/cephroot.txt @@ -0,0 +1,86 @@ +Mounting the root filesystem via Ceph (cephroot) +=============================================== + +Written 2013 by Rob Taylor + +derived from nfsroot.txt: + +Written 1996 by Gero Kuhlmann +Updated 1997 by Martin Mares +Updated 2006 by Nico Schottelius +Updated 2006 by Horms + + + +In order to use a diskless system, such as an X-terminal or printer server +for example, it is necessary for the root filesystem to be present on a +non-disk device. This may be an initramfs (see Documentation/filesystems/ +ramfs-rootfs-initramfs.txt), a ramdisk (see Documentation/initrd.txt), a +filesystem mounted via NFS or a filesystem mounted via Ceph. The following +text describes on how to use Ceph for the root filesystem. + +For the rest of this text 'client' means the diskless system, and 'server' +means the Ceph server. + + +1.) Enabling cephroot capabilities + ----------------------------- + +In order to use cephroot, CEPH_FS needs to be selected as +built-in during configuration. Once this has been selected, the cephroot +option will become available, which should also be selected. + +In the networking options, kernel level autoconfiguration can be selected, +along with the types of autoconfiguration to support. Selecting all of +DHCP, BOOTP and RARP is safe. + + +2.) Kernel command line + ------------------- + +When the kernel has been loaded by a boot loader (see below) it needs to be +told what root fs device to use. And in the case of cephroot, where to find +both the server and the name of the directory on the server to mount as root. +This can be established using the following kernel command line parameters: + +root=/dev/ceph + +This is necessary to enable the pseudo-Ceph-device. Note that it's not a +real device but just a synonym to tell the kernel to use Ceph instead of +a real device. + +If cephroot is not specified, it is expected that that a valid mount will be +found via DHCP option 17, Root Path [1] + +cephroot=:/[], + + Monitor addresses separated by commas. Each takes the form + host[:port]. If the port is not specified, the Ceph default + of 6789 is assumed. + + A subdirectory subdir may be specified if a subset of the file + system is to be mounted + + Standard Ceph options. All options are separated by commas. + See Documentation/filesystems/ceph/ceph.txt for options and + their defaults. + +4.) References + ---------- + +[1] http://tools.ietf.org/html/rfc2132 + +5.) Credits + ------- + + cephroot was derived from nfsroot by Rob Taylor + and Mark Doffman + + The nfsroot code in the kernel and the RARP support have been written + by Gero Kuhlmann . + + The rest of the IP layer autoconfiguration code has been written + by Martin Mares . + + In order to write the initial version of nfsroot I would like to thank + Jens-Uwe Mager for his help. -- 1.8.4