Remove double "it", and redundant information about defaults

[nbd.git] / README

diff --git a/README b/README
index da86a39..e2e7291 100644 (file)
--- a/README
+++ b/README
@@ -16,10 +16,18 @@ Using NBD is quite easy. First, on the client, you need to create the
 device nodes:
 
 # cd /dev
-# ./MAKEDEV nb0
+# ./MAKEDEV nbd0
 
-(if you need more than one NBD device, repeat the above command for nb1,
-nb2, ...)
+(if you need more than one NBD device, repeat the above command for nbd1,
+nbd2, ...)
+
+Since there's a problem with nbd and the (default) cfq I/O scheduler,
+you may want to set it to deadline:
+
+echo 'deadline' > /sys/block/nbd0/queue/scheduler
+
+(again, repeat the above for nbd1, nbd2, etc, if you need more than one
+device)
 
 Next, start the server. You can use a file or a block device for that:
 
@@ -39,7 +47,7 @@ nbd-client <hostname> <port> <nbd device>
 
 e.g.,
 
-nbd-client 10.0.0.1 1234 /dev/nb0
+nbd-client 10.0.0.1 1234 /dev/nbd0
 
 nbd-client must be ran as root; the same is not true for nbd-server (but
 do make sure that /var/run is writeable by the server that nbd-server
@@ -68,6 +76,8 @@ This configuration file is expected to be found at
        readonly = false
        multifile = false
        copyonwrite = false
+       prerun = dd if=/dev/zero of=%s bs=1k count=500
+       postrun = rm -f %s
 [otherexport]
        exportname = /export/nbd/experiment
        port = 12346
@@ -93,17 +103,12 @@ FreeBSD: "net/nbd-server", available in the ports tree since 2003.
        FreeBSD doesn't have kernel support for NBD, so obviously the
        client isn't built there.
 SuSE: "nbd", since SuSE 10.0
+Fedora: "nbd", since Fedora 7
+uClibc's "buildroot" script also seems to have support for NBD.
 
 If you're packaging NBD for a different operating system that isn't in
 the above list, I'd like to know about it.
 
-Thanks, and have fun,
-
-Wouter Verhelst
-
-
-
-
 [1] When you write something to a block device, the kernel will not
 immediately write that to the physical block device; instead, your
 changes are written to a cache, which is periodically flushed by a
@@ -114,3 +119,27 @@ more than one block device at the same time.
 If, while your kblockd is emptying the NBD buffer cache, the kernel
 decides that the cache of the block device your nbd-server is writing to
 needs to be emptied, then you've got a deadlock.
+
+A kernel patch exists to create a separate kernel thread for NBD writes
+which woul fix this problem; however, it has not made it into mainline
+yet.
+
+BUILDING THE SERVER FOR NON-LINUX OPERATING SYSTEMS
+===================================================
+
+Since the client requires kernel-side support, you can't just compile
+nbd-client on a non-Linux kernel and hope it'll work; you'd have to
+write a kernel-space driver before that would be possible.
+
+However, nbd-server assumes nothing more than POSIX and one headerfile
+from the Linux kernel. Compiling it can be done as follows:
+- Fetch the nbd userland sources, and unpack them. Since you're reading
+  this README file, you have already done this step.
+- Fetch the "nbd.h" file from /usr/include/linux on a Linux system, or
+  from include/linux in the Linux source tree, and store it in the
+  toplevel directory of the nbd userland sources
+- Edit the headerfile, and remove the line that says '#include
+  <linux/types.h>' (on non-Linux systems, the userland source is smart
+  enough to figure out how this works by itself)
+- now it's just a regular './configure && make && sudo make install'
+