Accessing ROOT Files Remotely via a rootd Server

Reading and writing ROOT files over the net can be done by creating a TNetFile object instead of a TFile object. Since the TNetFile class inherits from the TFile class it has exactly the same interface and behaviour. The only difference is that it reads and writes via a remote rootd daemon.

TNetFile URL

roots://hpsalo/files/aap.root
root://hpbrun.cern.ch/root/hsimple.root
root://pcna49a:5151/~na49/data/run821.root
root://pcna49d.cern.ch:5050//v1/data/run810.root

The only difference with the well known httpd URL's is that the root of the remote file tree is the remote user's home directory. Therefore an absolute pathname requires a // after the host or port specifier (as shown in the last example above). Further the expansion of the standard shell characters, like ~, $,.., etc. is handled as expected. The default port on which the remote rootd listens is 1094 and this default port is assumed by TNetFile (actually by TUrl which is used by TNetFile). Port number 1094 has officially been assigned by IANA for rootd.

The rootd Daemon

hpsalo [12] telnet fsgi02.fnal.gov
login: minuser
Password:
<fsgi02> rootd -p 5151
<fsgi02> exit
hpsalo [13] root
root [0] TFile *f = TFile::Open("root://fsgi02.fnal.gov:5151/file.root","new")
Name (fsgi02.fnal.gov:rdm): minuser
Password:
root [1] f.ls()

In the above example rootd runs on the remote node under user id minuser and listens to port 5151. When creating a TNetFile object you have to specify this same port number 5151 and use minuser (and corresponding password) as login id. When rootd is started in this way you can only login with the user id under which rootd was started on the remote machine. However, you can make many connections since the original rootd will fork (spawn) a new rootd that will service the requests from the TNetFile. The original rootd keeps listening on the specified port for other connections. Each time a TNetFile makes a connection it gets a new private rootd that will handle its requests. At the end of a root session when all TNetFiles are closed only the original rootd will stay alive ready to service future TNetFiles. fgfgf

Remote Authentication

Shadow Passwords

#! /usr/bin/perl
srand(time());
my $randletter = "(int (rand(26)) + (int (rand(1) + .5) % 2 ? 65 : 97))";
my $salt = sprintf("%c%c", eval $randletter, eval $randletter);
my $plaintext = shift;
my $crypttext = crypt($plaintext, $salt);
print "${crypttext}\n";

Using the General TFile::Open() Function

         TFile *TFile::Open(const Text_t *name, Option_t *option="",
                       const Text_t *title="",

Depending on the name argument the function returns either a TFile, a TNetFile or a TWebFile object. In case a TNetFile URL specifies a local file a TFile object will be returned (and of course no login information is needed). The arguments of the Open() function are the same as the ones for the TFile constructor.

A Sample Session

Starting rootd via inetd

rootd     1094/tcp

and to /etc/inetd.conf the line:

rootd stream tcp nowait root /usr/local/root/bin/rootd rootd -i

After these changes force inetd to reread its config file with "kill -HUP <pid inetd>".

Setup in this way it is not necessary to specify a port number in the URL given to TNetFile. TNetFile assumes the default port to be 1094 as specified above in the /etc/services file.

Systems using the new xinetd super daemon, like RedHat 7.0, should create a file /etc/xinetd.d/rootd with the following contents:

# default: on
# description: The rootd daemon allows remote access to ROOT files.
service rootd
{
        disable = no
        socket_type             = stream
        wait                    = no
        user                    = root
        server                  = /usr/local/root/bin/rootd
        server_args             = -i /usr/local/root
        log_on_success          += DURATION USERID
        log_on_failure          += USERID
}

Rootd Command Line Arguments

Similar command line arguments are accepted by proofd.
 

Anonymous rootd Usage

• Add the following line to /etc/passwd:

   rootd:*:71:72:Anonymous rootd:/var/spool/rootd:/bin/false

where you may modify the uid, gid (71, 72) and the home directory to suite your system.
• Add the following line to /etc/group:

   rootd:*:72:rootd

where the gid must match the gid in /etc/passwd.
• Create the directories:

   mkdir /var/spool/rootd
   mkdir /var/spool/rootd/tmp
   chmod 777 /var/spool/rootd/tmp

Where /var/spool/rootd must match the rootd home directory as specified in the rootd /etc/passwd entry.
• To make writeable directories for anonymous do, for example:

   mkdir /var/spool/rootd/pub
   chown rootd:rootd /var/spool/rootd/pub

Several remarks:

• you can login to an anonymous server either with the names "anonymous" or "rootd".
• the passwd should be of type user@host.do.main. Only the @ is enforced for the time being.
• in anonymous mode the top of the file tree is set to the rootd home directory, therefore only files below the home directory can be accessed.
• anonymous mode only works when the server is started via inetd.