用内核驱动挂载 CephFS

The CephFS kernel driver is part of the Linux kernel. It allows mounting CephFS as a regular file system with native kernel performance. It is the client of choice for most use-cases.

Prerequisites

Complete General Prerequisites

Go through the prerequisites required by both, kernel as well as FUSE mounts, in Mount CephFS: Prerequisites page.

Is mount helper is present?

mount.ceph helper is installed by Ceph packages. The helper passes the monitor address(es) and CephX user keyrings automatically saving the Ceph admin the effort to pass these details explicitly while mountng CephFS. In case the helper is not present on the client machine, CephFS can still be mounted using kernel but by passing these details explicitly to the mount command. To check whether it is present on your system, do:

stat /sbin/mount.ceph

哪个内核版本？

由于内核客户端是作为 Linux 内核的一部分发布的（不是随打包的 Ceph 二进制包发布），所以你得考虑客户端节点用哪个内核版本。已知比较老的内核所带的 Ceph 客户端有诸多缺陷，而且不一定支持近期 Ceph 集群所支持的功能。

需要注意的是， Linux 发行版的稳定分支里的“最新”内核可能会比最新的上游 Linux 内核晚好几年，而 Ceph 的开发是与上游内核同步的（包括缺陷修订）。

粗略地算，从 Ceph 10.x (Jewel) 起，你最好用 4.x 以上的内核。如果不得不用更老的内核，那你应该用 fuse 客户端，不要用内核客户端。

如果你的 Linux 发行版提供额外的 CephFS 技术支持，那就另当别论了，这时候发行者会负责把修订补丁移植到他们的稳定版内核：请与厂商核实。

Synopsis

In general, the command to mount CephFS via kernel driver looks like this:

mount -t ceph {device-string}:{path-to-mounted} {mount-point} -o {key-value-args} {other-args}

Mounting CephFS

On Ceph clusters, CephX is enabled by default. Use mount command to mount CephFS with the kernel driver:

mkdir /mnt/mycephfs
mount -t ceph :/ /mnt/mycephfs -o name=foo

The key-value argument right after option -o is CephX credential; name is the username of the CephX user we are using to mount CephFS. The default value for name is guest.

The kernel driver also requires MON’s socket and the secret key for the CephX user. In case of the above command, mount.ceph helper figures out these details automatically by finding and reading Ceph conf file and keyring. In case you don’t have these files on the host where you’re running mount command, you can pass these details yourself too:

mount -t ceph 192.168.0.1:6789,192.168.0.2:6789:/ /mnt/mycephfs -o name=foo,secret=AQATSKdNGBnwLhAAnNDKnH65FmVKpXZJVasUeQ==

Passing a single MON socket in above command works too. A potential problem with the command above is that the secret key is left in your shell’s command history. To prevent that you can copy the secret key inside a file and pass the file by using the option secretfile instead of secret:

mount -t ceph :/ /mnt/mycephfs -o name=foo,secretfile=/etc/ceph/foo.secret

Ensure the permissions on the secret key file are appropriate (preferably, 600).

In case CephX is disabled, you can omit -o and the list of key-value arguments that follow it:

mount -t ceph :/ /mnt/mycephfs

To mount a subtree of the CephFS root, append the path to the device string:

mount -t ceph :/subvolume/dir1/dir2 /mnt/mycephfs -o name=fs

If you have more than one file system on your Ceph cluster, you can mount the non-default FS as follows:

mount -t ceph :/ /mnt/mycephfs2 -o name=fs,fs=mycephfs2

Unmounting CephFS

To unmount the Ceph file system, use the umount command as usual:: 要卸载 Ceph 文件系统，和平时用 unmount 命令一样：

umount /mnt/mycephfs

Tip

执行此命令前确保你不在此文件系统目录下。

永久挂载

To mount CephFS in your file systems table as a kernel driver, add the following to /etc/fstab:

[{ipaddress}:{port}]:/ {mount}/{mountpoint} ceph [name=username,secret=secretkey|secretfile=/path/to/secretfile],[{mount.options}]

For example:

:/     /mnt/ceph    ceph    name=admin,noatime,_netdev    0       2

The default for the name= parameter is guest. If the secret or secretfile options are not specified then the mount helper will attempt to find a secret for the given name in one of the configured keyrings.

See User Management for details on CephX user management and mount.ceph manual for more options it can take. For troubleshooting, see 内核挂载的调试.