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| author | rsc <devnull@localhost> | 2005-01-14 03:45:44 +0000 |
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| committer | rsc <devnull@localhost> | 2005-01-14 03:45:44 +0000 |
| commit | 78e51a8c6678b6e3dff3d619aa786669f531f4bc (patch) | |
| tree | 015e00fde4fc837fd31b705e18d17dc913829388 /man/man4/intro.html | |
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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 @@ +<head> +<title>intro(4) - Plan 9 from User Space</title> +<meta content="text/html; charset=utf-8" http-equiv=Content-Type> +</head> +<body bgcolor=#ffffff> +<table border=0 cellpadding=0 cellspacing=0 width=100%> +<tr height=10><td> +<tr><td width=20><td> +<tr><td width=20><td><b>INTRO(4)</b><td align=right><b>INTRO(4)</b> +<tr><td width=20><td colspan=2> + <br> +<p><font size=+1><b>NAME </b></font><br> + +<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td> + + intro – introduction to file servers<br> + +</table> +<p><font size=+1><b>DESCRIPTION </b></font><br> + +<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td> + + A Plan 9 <i>file server</i> 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. + <table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table> + + In Plan 9, the kernel mount device <i>mnt</i>(3) acts as a client to + the 9P servers mounted in the current name space, translating + system calls such as <a href="../man2/open.html"><i>open</i>(2)</a> into 9P transactions such as <i>open</i>(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 <i>name space</i> 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. + <table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table> + + 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 <a href="../man3/9pclient.html"><i>9pclient</i>(3)</a> library to connect + and interact directly with particular 9P servers. The <a href="../man1/9p.html"><i>9p</i>(1)</a> command-line + client is useful for interactive use and in shell + scripts. + <table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table> + + To preserve the façade of a single 9P conversation with each server, + 9P servers invoke <a href="../man4/9pserve.html"><i>9pserve</i>(4)</a>, typically via <a href="../man3/post9pservice.html"><i>post9pservice</i>(3)</a>. + <i>9pserve</i> 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. + <table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table> + + 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 <tt><font size=+1>/tmp/ns.$USER.$DISPLAY</font></tt>, + meaning that all programs in an X + Windows login session share a single name space. Setting the <tt><font size=+1>$NAMESPACE</font></tt> + environment variable overrides this default. The <a href="../man1/namespace.html"><i>namespace</i>(1)</a> + command prints the current name space directory. + <table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table> + + 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 <i>openfd</i>(9p) 9P transaction, which depends on file descriptor + passing, provides a sufficient workaround in many cases. <i>9pserve</i>’s + implementation of <i>openfd</i> (see also <i>fsopenfd</i> in + <a href="../man3/9pclient.html"><i>9pclient</i>(3)</a>) 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. + +</table> + +<td width=20> +<tr height=20><td> +</table> +<!-- TRAILER --> +<table border=0 cellpadding=0 cellspacing=0 width=100%> +<tr height=15><td width=10><td><td width=10> +<tr><td><td> +<center> +<a href="../../"><img src="../../dist/spaceglenda100.png" alt="Space Glenda" border=1></a> +</center> +</table> +<!-- TRAILER --> +</body></html> |