Chirp is Copyright (C) 2003-2004 Douglas Thain and Copyright (C) 2005- The University of Notre Dame. All rights reserved. This software is distributed under a BSD-style license. See the file COPYING for details.
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Chirp is like a distributed filesystem (such as NFS) except that it can be run over wide area networks and requires no special privileges on either the client or the server end. Chirp allows the end user to set up fine-grained access control so that data can be shared (or not shared) with the right people.
Chirp is also like a file transfer system (such as FTP) that provides streaming point-to-point data transfer over the Internet. However, Chirp also provides fine-grained Unix-like data access suitable for direct access by ordinary programs.
Chirp also allows the secure remote execution of programs on stored data. This technique is known as PINS -- Processing IN Storage. A novel security mechanism allows programs and data to be associated with external grid identities. Note that this feature must be explicitly enabled, so you don't have to worry about it if you are only interested in storage. Read on below for more details.
Begin by installing the cctools on your system. When you are ready, proceed below.
/tmp/mydata
% chirp_server -r /tmp/mydata &
% chirp localhost chirp:localhost:/> setacl . hostname:*.mydomain.edu write
% parrot tcsh % cd /chirp % ls angband.somewhere.edu:9094 dustpuppy.somewhere.edu:9094 peanuts.somewhere.edu:9094 ... % cd /chirp/peanuts.somewhere.edu % cp /tmp/bigfile . % ls -la total 804 drwx------ 2 fred users 4096 Sep 10 12:40 . drwx------ 2 fred users 4096 Sep 10 12:40 .. -rw-r--r-- 1 fred users 104857600 Sep 10 12:57 bigfile -rw-r--r-- 1 fred users 147 Sep 10 12:39 hosts % cp /http/www.cse.nd.edu temp.html % vi temp.html % |
(If you are having difficulting accessing your server, have a look at "debugging hints" below.)
Parrot is certainly the most convenient way to access storage, but it has some limitations: it only works on Linux, and it imposes some performance penalty. For more portable, explicit control of a Chirp server, use the Chirp command line tool. This allows you to connect to a server, copy files, and manage directories, much like an FTP client:
% chirp ... chirp::> open myhost.somewhere.edu chirp:myhost.somewhere.edu:/> put /tmp/bigfile file /tmp/bigfile -> /bigfile (11.01 MB/s) chirp:myhost.somewhere.edu:/> ls -la dir 4096 . Fri Sep 10 12:40:27 2004 dir 4096 .. Fri Sep 10 12:40:27 2004 file 147 hosts Fri Sep 10 12:39:54 2004 file 104857600 bigfile Fri Sep 10 12:53:21 2004 chirp:myhost.somewhere.edu:/> |
In scripts, you may find it easier to use the standalone commands chirp_get and chirp_put, which move single files to and from a Chirp server. These commands also allow for streaming data, which can be helpful in a shell pipeline. Also, the -f option to both commands allows you to follow a file, much like the Unix tail command:
% tar cvzf archive.tar.gz ~/mydata % chirp_put archive.tar.gz myhost.somewhere.edu archive.tar.gz % ... % chirp_get myhost.somewhere.edu archive.tar.gz - | tar xvzf % ... % chirp_get -f myhost.somewhere.edu logfile - |& less % |
The fourth way to access the storage pool is write your own programs that access the Chirp C interface. Download a source package and examine chirp/src/chirp_reli.h. This interface is relatively self explanatory: programs written to use this library may perform explicit I/O operations in a manner very similar to Unix.
The storage catalog is highly dynamic. By default, each Chirp server makes itself known to the storage catalog every five minutes. The catalog server records and reports all Chirp servers that it knows about, but will discard servers that have not reported for fifteen minutes.
If you do not want your servers to report to a catalog, then run them with this option:
% chirp_server -u -
Alternatively, you may establish your own catalog server. This can be useful for keeping your systems logically distinct from the main storage pool, but can also help performance and availability if your catalog is close to your Chirp servers. The catalog server is installed in the same place as the Chirp server. Simply run it on any machine that you like and then direct your Chirp servers to update the new catalog with the -u option. The catalog will be published via HTTP on port 9097 of the catalog machine.
For example, suppose that you wish to run a catalog server on a machine named dopey and a Chirp server on a machine named sneezy:
dopey% catalog_server ... sneezy% chirp_server -u dopey [more options]Finally, point your web browser to:
http://dopey:9097Or, set an environment variable and use Parrot:
% setenv CATALOG_HOST dopey % parrot tcsh % ls /chirpAnd you will see something like this. You may easily run multiple catalogs for either scalability or fault tolerance. Simply give each Chirp server multiple -u options to name each running catalog.
Security really has two aspects: authentication and authorization. Authentication deals with the question "Who are you?" Once your identity has been established, then authorization deals with the question "What are you allowed to do?" Let's deal with each in turn.
| Type | Summary | Regular User? | Root? |
| (non-root) | (root) | ||
| kerberos | Centralized private key system | no | yes (host cert) |
| globus | Distributed public key system | yes (user cert) | yes (host cert) |
| unix | Authenticate with local unix user ids. | yes | yes |
| hostname | Reverse DNS lookup | yes | yes |
| address | Identify by IP address | yes | yes |
The Chirp tools will attempt all of the authentication types that are known and available in the order above until one works. For example, if you have Kerberos installed in your system, Chirp will try that first. If not, Chirp attempts the others.
Once an authentication scheme has succeeded, Chirp assigns the incoming user a subject that describes both the authentication method and the user name within that method. For example, a user that authenticates via Kerberos might have the subject:
kerberos:dthain@nd.edu
A user authenticating with Globus credentials might be:
globus:/O=Cooperative_Computing_Lab/CN=Douglas_L_Thain
While another user authenticating by local unix ids might be:
unix:dthain
While a user authenticating by simple hostnames might be:
hostname:pigwidgeon.cse.nd.edu
Take note that Chirp considers all of the subjects as different
identities, although some of them might correspond to the same
person in varying circumstances.
Every directory in a Chirp server has an ACL, much like in some filesystems such as as AFS or NTFS. To see the ACL for a directory, use the Chirp tool and the getacl command:
chirp:localhost:/> getacl unix:dthain rwla hostname:*.mydomain.edu rwlThis ACL indicates that the subject unix:dthain has all five access rights, while the subject pattern hostname:*.mydomain.edu has only three access rights. The access rights are as follows:
| r | - The subject may read items in the directory. |
| w | - The subject may write and delete items in the directory. |
| l | - The subject may list the directory contents. |
| x | - The subject may execute programs in the directory. |
| v | - The subject may reserve a directory. |
| a | - The subject may administer the directory, including changing the ACL. |
Access rights often come in combinations, so there are a few aliases for your convenience:
| read | - alias for rl |
| write | - alias for rwl |
| admin | - alias for rwla |
| none | - delete the entry |
chirp:localhost:/> setacl / kerberos:dthain@nd.edu write chirp:localhost:/> getacl unix:dthain rwla hostname:*.mydomain.edu rwl kerberos:dthain@nd.edu rwlThe meaning of ACLs is fairly obvious, but there are few subtleties you should know:
Rights are generally inherited. When a new directory is created, it automatically gets the ACL of its parent. Exception: read about the reserve right below.
Rights are generally not hierarchical. In order to access a directory, you only need the appropriate permissions on that directory. For example, if you have permission to write to /data/x/y/z, you do not need any other permissions on /data, /data/x and so forth. Of course, it may be difficult to discover a deep directory without rights on the parents, but you can still access it.
The delete right is absolute. If you have permission to delete a directory, then you are able to delete the entire subtree that it contains, regardless of any other ACLs underneath.
Note that it is possible to use Chirp to export an existing directory tree without manually populating every directory with ACLs. Simply create an ACL in an external file, and then use the -A option to tell the Chirp server to use that file as the default ACL.
A shared-storage environment such as Chirp aims to allow many people to read and write common storage space. Of course, with many people reading and writing, we need some mechanism to make sure that everybody does not step on each other's toes.
The reserve right allows a user to create what is essentially a fresh workspace for their own use. When a user creates a new directory and has the v right (but not the w right), Chirp will create a new directory with a fresh ACL that gives the creating user restricted rights.
A good way to use the reserve right is with a wildcard at the top directory. Here's an example. Suppose that Fred creates a new Chirp server on the host bigwig. Initially, no-one except Fred can access the server. The first time it starts, the Chirp server initializes its root directory with the following ACL:
unix:fred rwlaNow, Fred wants other users in his organization to be able to use this storage, but doesn't want them messing up his existing data. So, Fred uses the Chirp tool to give the list (l) and reserve (v) rights to anyone calling from any machine in his organization:
chirp:bigwig:> setacl / hostname:*.somewhere.edu lv(rwla) chirp:bigwig:> getacl / unix:fred rwla hostname:*.somewhere.edu lv(rwla)Now, any user calling from anywhere in somewhere.edu can access this server. But, all that any user can do is issue ls or mkdir in the root directory. For example, suppose that Betty logs into this server from ws1.somewhere.edu. She can not modify the root directory, but she can create her own directory:
chirp:bigwig:> mkdir /mydataAnd, in the new directory, ws1.somewhere.edu can do anything, including edit the access control. Here is the new ACL for /mydata:
chirp:bigwig:> getacl /mydata hostname:ws1.somewhere.edu rwlaIf Betty wants to authenticate with Globus credentials from here on, she can change the access control as follows:
chirp:bigwig:> setacl /mydata globus:/O=Univ_of_Somewhere/CN=Betty rwlaAnd, the new acl will look as follows:
chirp:bigwig:> getacl /mydata hostname:ws1.somewhere.edu rwla globus:/O=Univ_of_Somewhere/CN=Betty rwla
Kerberos: The server will attempt to use the Kerberos identity of the host it is run on. (i.e. host/coral.cs.wisc.edu@CS.WISC.EDU) Thus, it must be run as the superuser in order to access its certificates. Once authentication is complete, there is no need for the server to keep its root access, so it will change to any unprivileged user that you like. Use the -i option to select the userid.
Globus: The server and client will attempt to perform client authentication using the Grid Security Infrastructure (GSI)> Both sides will load either user or host credentials, depending on what is available. If the server is running as an ordinary user, then you must give a it a proxy certificate with grid-proxy-init. Or, the server can be run as root and will use host certificates in the usual place.
Unix: This method makes use of a challenge-response in the local Unix filesystem to determine the client's Unix identity. It assumes that both machines share the same conception of the user database and have a common directory which they can read and write. By default, the server will pick a filename in /tmp, and challenge the client to create that file. If it can, than the server will examine the owner of the file to determine the client's username. Naturally, /tmp will only be available to clients on the same machine. However, if a shared filesystem directory is available, give that to the chirp server via the -c option. Then, any authorized client of the filesystem can authenticate to the server. For example, at Notre Dame, we use -c /afs/nd.edu/user37/ccl/software/rendezvous to authenticate via our AFS distributed file system.
Hostname: The server will rely on a reverse DNS lookup to establish the fully-qualified hostname of the calling client. The second field gives the hostname to be accepted. It may contain an asterisk as a wildcard. The third field is ignored. The fourth field is then used to select an appropriate local username.
Address: Like "hostname" authentication, except the server simply looks at the client's IP address.
By default, Chirp and/or Parrot will attempt every authentication type knows until one succeeds. If you wish to restrict or re-order the authentication types used, give one or more -a options to the client, naming the authentication types to be used, in order. For example, to attempt only hostname and kerberos authentication, in that order:
% chirp -a hostname -a kerberos
By default, a Chirp server allows only for data storage. Program execution must be manually enabled through two distinct steps:
To execute a program remotely, create a fresh directory, ensure that you have the X right on the directory, and transfer in a program. Use the exec command from the Chirp tool to execute the program. The first three arguments to exec are the standard input, output, and error files for the program. (Use a plain - to indicate no file needed.) The remaining arguments are the program to be run, along with it's arguments. After the program completes, extract or modify using Parrot or Chirp as needed.
As a very simple example, suppose that you want to sort some data stored in /chirp/server.nd.edu/data/records.txt. Using the Chirp tool, set the X right, send the sort binary, and then execute it:
% chirp server.nd.edu connected to server.nd.edu:9094 as unix:fred chirp:server.nd.edu> setacl . unix:fred rwlax chirp:server.nd.edu> put /bin/sort chirp:server.nd.edu> exec records.txt sorted.txt error.txt sort -nNow, the sorted records are found in sorted.txt. You could extract the data for further manipulation, or you could simply dispatch further programs like grep to sort it:
chirp:server.nd.edu> put /bin/grep chirp:server.nd.edu> exec sorted.txt matched.txt error.txt grep needleThe Chirp security model allows for many flexible policies on what programs may be run. The owner of a server can allow a user to run and execute arbitrary code on a server by granting the W and X rights on a directory. If the owner wants to restrict the runnable programs, he/she may provide a directory of programs with only the R and X bits set. This allows users to execute only those programs provided. By constructing ACLs appropriately, various classes of users may be given different policies.
Note that the same security model is used for both data access as remote execution. Internally, Chirp uses Parrot to run the program in an identity box that ensures it can only access files according to the ACLs as described above. If you were to dispatch the program whoami to the remote node, you would see the same identity you used to authenticate to the Chirp server. Thus, it is not necessary for any special accounts to be created for visiting users.
In all of the Chirp and Parrot tools, the -d option allows you to turn on selected debugging messages. The simplest option is -d all which will show every event that occurs in the system.
To best debug a problem, we recommend that you turn on the debugging options on both the client and server that you are operating. For example, if you are having trouble getting Parrot to connect to a Chirp server, then run both as follows:
% chirp_server -d all [more options] ... % parrot -d all tcshOf course, this is likely to show way more information than you will be able to process. Instead, turn on a debugging flags selectively. For example, if you are having a problem with authentication, just show those messages with -d auth on both sides.
There are a large number of debugging flags. Currently, the choices are: syscall notice channel process resolve libcall tcp dns auth local http ftp nest chirp dcap rfio cache poll remote summary debug time pid all. When debugging problems with Chirp and Parrot, we recommend selectively using -d chirp, -d tcp, -d auth, and -d libcall as needed.