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This requires a considerable amount of work, and expertise with many different package formats. You can install a binary release of OPAM on most systems by first installing the "0install" package from your distribution "zeroinstall-injector" on older distributions and then adding OPAM.
If you already have an opam command but want to try the 0install version anyway, just give it a different name e. Here, we are telling 0install to create a local command called opam that runs the program http: You can see where it put OPAM with the "show" command:. OPAM depends on two other programs: In this case, 0install has satisfied the curl dependency using an official Fedora package, but needed to install aspcud using 0install.
On Arch Linux, it can use distribution packages for both. You can upgrade or downgrade the package by adding a version constraint. By default, 0install prefers the "stable" version of a program:. You could do as it suggests and tell it to prefer testing versions globally, or you can add a version constraint if you just want to affect this one program:.
You can also specify an upper bound --before or a fixed version --version if you prefer. You can control the versions of dependencies with --version-for.
By the way, 0install supports tab-completion everywhere: Finally, if an upgrade stops a program from working then you can use whatchanged to see the latest changes:. If you visit http: If you view the source in your browser, you'll see that it's actually an XML document with a stylesheet providing the formatting. It can be run by executing the opam binary within the archive.
It depends on aspcud and curl , which live in other repositories ideally, these would be the official project sites for these programs, but currently they are provided by a third party.
In both cases, we tell OPAM about the chosen version by setting an environment variable. Lower down there is a more complex entry saying how to build from source, which provides a way to generate more binaries, and the XML is followed by a GPG signature block formatted as an XML comment so that the document is still valid XML.
When you use a program for the first time, 0install downloads the signing GPG key and checks it with the key information service.
If this service knows the key, it saves it as a trusted key for that site. If not, it prompts you to confirm. In future, it will check that all updates from that site are signed with the same key, prompting you if not much like ssh does. Ideally, OPAM's own Git repository would contain an XML file describing its build and runtime dependencies curl and aspcud in this case and how to build binaries from it. We would then generate the XML for releases from it automatically using tools such as 0release.
However, when trying out 0install you may prefer to package up an existing binary release, and this is what I did for OPAM. The simplest case is that the binary is in the current directory. In this case, the XML just describes its dependencies and how to run it, but not how to download the program.
You can create a template XML file using 0template or just write it yourself:. Now we need a way to generate similar XML for released archives on the web. Finally, you can submit the XML to a repository which is easy to host yourself using the 0repo tool:.
There are simpler ways to get the signed XML, e. There are plenty of ways to extend this. For the OPAM 1. For my own software, I commit an XML file saying how to build it to my Git repository and let 0release handle the whole release process from tagging the Git repository, to building the binaries in various VMs, to publishing the archives and the final signed XML.
In the future, we hope to integrate this with OPAM so that source and binary releases can happen together. For example, I have used 0install to manage Xen images of Mirage unikernels. This command shows the latest binary of the mir-hello unikernel for Xen downloading it first if needed:. It is useful to distribute binary executables in cases where users shouldn't have to compile from source. It supports GPG signature checking, automatic updates, pinned versions and parallel installations of multiple versions.
A single package format is sufficient for all platforms you still need to create separate binary archives for e. OS X and Linux, of course. Packages are named by URI and the metadata is downloaded directly from the named repository. There are some extra services such as the default mirror service , the search service and the key information service , but these are all optional.
Using 0install to get OPAM means that all platforms can be supported without the need to package separately for each one, and users who don't wish to install as root still get signature checking, dependency handling and automatic updates. We hope that 0install will make it easier for you to distribute binaries of your own applications.
My talk at OCaml video , slides gives more information about 0install and its conversion to OCaml. Binary distribution with 0install On , by Thomas Leonard.