term% ls -F
term% cat index.txt
ATTACH(5)                     File Formats Manual                    ATTACH(5)

       attach, auth - messages to establish a connection

       size[4] Tauth tag[2] afid[4] uname[s] aname[s]
       size[4] Rauth tag[2] aqid[13]

       size[4] Tattach tag[2] fid[4] afid[4] uname[s] aname[s]
       size[4] Rattach tag[2] qid[13]

       The  attach  message  serves as a fresh introduction from a user on the
       client machine to the server.  The message identifies the user  (uname)
       and  may  select  the  file  tree to access (aname).  The afid argument
       specifies a fid previously established by an auth message, as described

       As  a  result of the attach transaction, the client will have a connec‐
       tion to the root directory of the desired  file  tree,  represented  by
       fid.  An error is returned if fid is already in use.  The server's idea
       of the root of the file tree is represented by the returned qid.

       If the client does not wish to authenticate the  connection,  or  knows
       that  authentication is not required, the afid field in the attach mes‐
       sage should be set to NOFID, defined as (u32int)~0  in  <fcall.h>.   If
       the  client  does wish to authenticate, it must acquire and validate an
       afid using an auth message before doing the attach.

       The auth message contains afid, a new fid to be established for authen‐
       tication,  and  the uname and aname that will be those of the following
       attach message.  If the server does not require authentication, it  re‐
       turns Rerror to the Tauth message.

       If  the  server does require authentication, it returns aqid defining a
       file of type QTAUTH (see intro(5)) that may be read and written  (using
       read  and write messages in the usual way) to execute an authentication
       protocol.  That protocol's definition is not part of 9P itself.

       Once the protocol is complete, the same afid is presented in the attach
       message  for  the user, granting entry.  The same validated afid may be
       used for multiple attach messages with the same uname and aname.

       An attach transaction will be generated for  kernel  devices  (see  in‐
       tro(3)) when a system call evaluates a file name beginning with Pipe(2)
       generates an attach on the kernel device  pipe(3).   The  mount  system
       call  (see  bind(2))  generates  an  attach  message to the remote file
       server.  When the kernel boots, an attach is made to the  root  device,
       root(3),  and  then  an attach is made to the requested file server ma‐

       An auth transaction is generated by the fauth(2) system call or by  the
       first mount system call on an uninitialized connection.

       auth(2), fauth(2), version(5), authsrv(6)