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author | Ingo Molnar <mingo@elte.hu> | 2008-11-20 09:03:38 +0100 |
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committer | Ingo Molnar <mingo@elte.hu> | 2008-11-20 09:03:38 +0100 |
commit | 90accd6fabf9b2fa2705945a4c601877a75d43bf (patch) | |
tree | d393cb54f0228b1313139e4e14adf4f5cf236b59 /Documentation/blockdev/nbd.txt | |
parent | b43d196c4d3fe46d6dda7c987c47792612b80b1b (diff) | |
parent | ee2f6cc7f9ea2542ad46070ed62ba7aa04d08871 (diff) |
Merge branch 'linus' into x86/memory-corruption-check
Diffstat (limited to 'Documentation/blockdev/nbd.txt')
-rw-r--r-- | Documentation/blockdev/nbd.txt | 47 |
1 files changed, 47 insertions, 0 deletions
diff --git a/Documentation/blockdev/nbd.txt b/Documentation/blockdev/nbd.txt new file mode 100644 index 00000000000..aeb93ffe641 --- /dev/null +++ b/Documentation/blockdev/nbd.txt @@ -0,0 +1,47 @@ + 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. |