mirror of
https://github.com/edk2-porting/linux-next.git
synced 2024-12-23 04:34:11 +08:00
48 lines
1.9 KiB
Plaintext
48 lines
1.9 KiB
Plaintext
|
Network Block Device (TCP version)
|
||
|
|
|
||
|
|
What is it: With this compiled in the kernel (or as a module), Linux
|
||
|
|
can use a remote server as one of its block devices. So every time
|
||
|
|
the client computer wants to read, e.g., /dev/nb0, it sends a
|
||
|
|
request over TCP to the server, which will reply with the data read.
|
||
|
|
This can be used for stations with low disk space (or even diskless -
|
||
|
|
if you boot from floppy) to borrow disk space from another computer.
|
||
|
|
Unlike NFS, it is possible to put any filesystem on it, etc. It should
|
||
|
|
even be possible to use NBD as a root filesystem (I've never tried),
|
||
|
|
but it requires a user-level program to be in the initrd to start.
|
||
|
|
It also allows you to run block-device in user land (making server
|
||
|
|
and client physically the same computer, communicating using loopback).
|
||
|
|
|
||
|
|
Current state: It currently works. Network block device is stable.
|
||
|
|
I originally thought that it was impossible to swap over TCP. It
|
||
|
|
turned out not to be true - swapping over TCP now works and seems
|
||
|
|
to be deadlock-free, but it requires heavy patches into Linux's
|
||
|
|
network layer.
|
||
|
|
|
||
|
|
For more information, or to download the nbd-client and nbd-server
|
||
|
|
tools, go to http://nbd.sf.net/.
|
||
|
|
|
||
|
|
Howto: To setup nbd, you can simply do the following:
|
||
|
|
|
||
|
|
First, serve a device or file from a remote server:
|
||
|
|
|
||
|
|
nbd-server <port-number> <device-or-file-to-serve-to-client>
|
||
|
|
|
||
|
|
e.g.,
|
||
|
|
root@server1 # nbd-server 1234 /dev/sdb1
|
||
|
|
|
||
|
|
(serves sdb1 partition on TCP port 1234)
|
||
|
|
|
||
|
|
Then, on the local (client) system:
|
||
|
|
|
||
|
|
nbd-client <server-name-or-IP> <server-port-number> /dev/nb[0-n]
|
||
|
|
|
||
|
|
e.g.,
|
||
|
|
root@client1 # nbd-client server1 1234 /dev/nb0
|
||
|
|
|
||
|
|
(creates the nb0 device on client1)
|
||
|
|
|
||
|
|
The nbd kernel module need only be installed on the client
|
||
|
|
system, as the nbd-server is completely in userspace. In fact,
|
||
|
|
the nbd-server has been successfully ported to other operating
|
||
|
|
systems, including Windows.
|