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In the earlier chapters, you learned how to create your first archive, start a project, check in the initial sources and subsequent changes, and retrieve past revisions.
In this chapter you'll learn how to make an archive available over a network and begin to learn how multiple programmers can share a single archive.
As you should recall, an archive has both a logical name, and a physical location:
% larch archives lord@emf.net--2003-example ^^^^^^^^^^^^^^^^^^^^^^^^^^ | /usr/lord/{archives}/2003-example | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | | | archive location | archive name
(See Creating a New Archive.)
Some archives can be accessed over a network, currently via any of the protocols:
FTP SFTP WebDAV plain HTTP
Later in this chapter, you'll learn how to create such archives.
For now, you should know that to access such an archive, you register it's name and physical location, using a URL for the physical location.
For example, to access an HTTP or WebDAV archive:
% larch register-archive lord@emf.net--2003 \ http://regexps.srparish.net/{archives}/lord@emf.net--2003
or an FTP archive:
% larch register-archive lord@regexps.com--2002 \ ftp://ftp.regexps.com/{archives}/lord@regexps.com--2002
You can see that these commands have taken effect:
% larch archives lord@emf.net--2003 http://regexps.srparish.net/{archives}/lord@emf.net--2003 lord@emf.net--2003-example /usr/lord/examples/{archives}/2003-example lord@regexps.com--2002 ftp://ftp.regexps.com/{archives}/lord@regexps.com--2002
After you've registered additional archives, how do you access them?
One trivial way is to make the archive you are interested in your default:
% larch my-default-archive lord@emf.net--2003 % larch categories [...categories in the remote archive...]
It can, of course, be inconvenient to keep changing your default archive. So for now, let's restore it to the archive we've been using in the examples:
% larch my-default-archive lord@emf.net--2003-example
There are two other ways to access a remote archive:
Every command that operates on archives accepts a -A
option which
can be used to override the default:
% larch my-default-archive lord@emf.net--2003-example % larch categories -A lord@emf.net--2003 [... categories in lord@emf.net--2003 ...]
Usage Note: A -A
argument takes precedence over your default
archive but is overridden by fully qualified project names (see
below).
Commands that accept project names allow you to use fully qualified project names . A fully qualified name is formed by prefixing an archive name, followed by a slash, to the project name:
category name: arch => lord@emf.net--2003/arch branch name: arch--devo => lord@emf.net--2003/arch--devo version name: arch--devo--1.0 => lord@emf.net--2003/arch--devo--1.0 revision name: arch--devo--1.0--patch-1 => lord@emf.net--2003/arch--devo--1.0--patch-1
As in this example:
% larch my-default-archive lord@emf.net--2003-example % larch branches lord@emf.net--2003/arch [... branches of arch in lord@emf.net--2003 ...]
Usage Note: A fully qualified name takes precedence over both -A
arguments and your default archive.
Operating system and server access controls can be used to limit some or all users to read-only access. For example, FTP is usually configured in such a way that anonymous users can read, but not modify the archive.
Upcoming Change Warning: The mechanism described in this section is going to change in future releases. Mirrors will be more cleanly supported. Nevertheless, this mechanism is currently widely adopted since it works well enough to get work done.
One popular way to use arch
is to use a local (i.e. not network
accessible) archive for day-to-day work, but then to "publish" that
archive on the network by creating an
archive mirror
.
A mirror is created by:
1) Creating an initially empty network-accessible archive.
2) Storing a file called =mirror
in the =meta-data
directory
in the root of the remote archive. That file should contain one line:
the name of the archive being mirrored.
3) Using the command larch push-mirror
to copy data from the
local archive to the mirror:
% larch push-mirror lord@emf.net--2003 lord@emf.net--2003-mirror [....]
Usage Note: Users do not generally run push-mirror
by hand.
Instead, they create something called a notifier that optimizes
push-mirror
by keeping track of what parts of the archive have
previously been copied. You'll learn more about notifiers in a later
chapter (see xref
Driving Process Automation with arch Notifiers
).
Usage Note: When you tell other people about your network accessible mirror, tell them to register it under the name of your local archive. As far as remote users are concerned, the mirror is the same thing as your local archive.
There is nothing to prevent you from making a single archive available
via multiple access methods. For example, you can register an FTP
accessible archive using a local-filesystem location on the machine
that contains the FTP directory, but ask other users to register it
with an ftp:
URL.
An archive is made FTP accessible simply by putting its directory in a location where an FTP server can make it available.
Security Cautions: When creating an FTP accessible archive, there are two important security concerns: passwords in the clear, and FTP server configuration.
Passwords in the Clear As is well known, the FTP protocol sends passwords across networks unencrypted. In many situations, that is considered an unacceptable security risk and you will therefore want to consider using FTP access only for public data, and then only for read-only access.
FTP Server Configuration In general, securely configuring an FTP server requires care, caution, and careful study of the relevant documentation for the operating system and server implementation you will be using.
[This isn't documented yet.]
[This isn't documented yet.]
arch Meets hello-world: A Tutorial Introduction to The arch Revision Control Systemregexps.com