From 78e51a8c6678b6e3dff3d619aa786669f531f4bc Mon Sep 17 00:00:00 2001 From: rsc Date: Fri, 14 Jan 2005 03:45:44 +0000 Subject: checkpoint --- man/man4/intro.html | 92 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 92 insertions(+) create mode 100644 man/man4/intro.html (limited to 'man/man4/intro.html') diff --git a/man/man4/intro.html b/man/man4/intro.html new file mode 100644 index 00000000..ec2409c0 --- /dev/null +++ b/man/man4/intro.html @@ -0,0 +1,92 @@ + +intro(4) - Plan 9 from User Space + + + + +
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INTRO(4)INTRO(4) +
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+

NAME
+ +
+ + intro – introduction to file servers
+ +
+

DESCRIPTION
+ +
+ + A Plan 9 file server provides a file tree to processes. This section + of the manual describes servers that can be mounted in a name + space to give a file-like interface to interesting services. A + file server may be a provider of a conventional file system, with + files maintained on permanent storage, or it may also be a process + that synthesizes files in some manner. +
+ + In Plan 9, the kernel mount device mnt(3) acts as a client to + the 9P servers mounted in the current name space, translating + system calls such as open(2) into 9P transactions such as open(9p). + The kernel also multiplexes the potentially many processes onto + a single 9P conversation with each server. Finally, the kernel + provides each process with its own private name space which it + can customize at will. Modern Unix systems do not provide these + niceties, so the Unix port of these Plan 9 file servers provides + them via other means. +
+ + On Unix, 9P clients do not access servers via the traditional + file system call interface. Only the Unix name space can be accessed + that way. Instead, 9P clients use the 9pclient(3) library to connect + and interact directly with particular 9P servers. The 9p(1) command-line + client is useful for interactive use and in shell + scripts. +
+ + To preserve the façade of a single 9P conversation with each server, + 9P servers invoke 9pserve(4), typically via post9pservice(3). + 9pserve announces a 9P service at a particular network address + and multiplexes the clients that connect to that address onto + a single 9P conversation with the server. +
+ + Each ported program operates in a pseudo-name space that determines + which 9P servers it is using. The name space of a ported program + is represented by a directory containing Unix domain sockets, + one for each 9P server. The directory defaults to /tmp/ns.$USER.$DISPLAY, + meaning that all programs in an X + Windows login session share a single name space. Setting the $NAMESPACE + environment variable overrides this default. The namespace(1) + command prints the current name space directory. +
+ + Occasionally it is useful to be able to connect the input or output + of a standard Unix program to a file served by a 9P server. The + new openfd(9p) 9P transaction, which depends on file descriptor + passing, provides a sufficient workaround in many cases. 9pserve’s + implementation of openfd (see also fsopenfd in + 9pclient(3)) returns the read or write end of a pipe; a helper + process transfers data between the other end of the pipe and the + 9P server. Note that since the data is being transferred via a + pipe, 9P read and write errors cannot be passed on to the Unix + program. The Unix program sees only end-of-file or a closed pipe. + +
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+ + +
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+
+Space Glenda +
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+ + -- cgit v1.2.3