Note: I developed this library in 2010. Its goal was to allow installers of third-party Linux apps to integrate with the native package system in a distro-independent manner. This idea was based on the so-called Berlin Packaging API proposal, which was formulated at a Linux Standard Base face-to-face meeting in 2006. My plan with the Psys library was to provide a useful proof-of-concept implementation which could later serve as basis for an standardized LSB interface.
I have since given up on that effort, though, and didn't develop the library any further in the last years, with the consequence that its package-manager-specific backends don't build anymore due to library changes (I developed this under Ubuntu 10.04!). However, as the idea and code might be of interest for some, I have decided to migrate the code and documentation to GitHub, where it is probably more easily found these days than at its original place at Gitorious. The accompanying discussions on lsb-discuss might also be of interest.
Below is the original README, converted to Markdown and augmented
with an example program that was originally only in the
documentation. The man pages in the doc/ directory can be found in
Markdown format in the wiki.
The psys library provides a simple interface to the system package manager of a Linux system. It allows installation programs to notify the package manager of the installation, uninstallation and update of third-party software packages, and to request these packages to be added to or removed from the system package database. The psys library interface is generic and not tied to a specific package management system or Linux distribution.
Note that the psys library is only useful for adding and removing
software which complies to the
Linux Standard Base (LSB)
specification. Most notably, it is assumed that the data files of a
software package are installed into /opt as demanded by the
Filesystem Hierarchy Standard (FHS),
and that a package only depends on the interfaces and behavior
specified by the LSB; any additional dependencies must be contained
within the package itself.
The psys library interface is strongly influenced by the ["Berlin Packaging API"]([3] http://www.linuxfoundation.org/en/Berlin_Packaging_API) concept [3] discussed at the 2006 LSB face-to-face meeting in Berlin. The library interface is meant as a proposal for a future version of the LSB standard.
The following program installs a simple hello world program and registers it as a packate in the distribution's package system.
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <psys.h>
#define HELLOWORLD_SCRIPT \\
"#!/bin/sh \\n" \\
"echo \\"Hello World!\\""
static void install_dir(const char *name)
{
if (mkdir(name, 0755) && errno != EEXIST) {
perror("mkdir()");
abort();
}
}
static void install(void)
{
FILE *f;
install_dir("/opt/example.com");
install_dir("/opt/example.com/helloworld");
install_dir("/opt/example.com/helloworld/bin");
f = fopen("/opt/example.com/helloworld/bin/helloworld", "w");
if (!f) {
perror("fopen()");
abort();
}
if (fputs(HELLOWORLD_SCRIPT, f) == EOF) {
perror("fputs()");
abort();
}
fclose(f);
if (chmod("/opt/example.com/helloworld/bin/helloworld", 0755)) {
perror("chmod()");
abort();
}
}
int main(int argc, char **argv)
{
psys_pkg_t pkg;
psys_err_t err = NULL;
pkg = psys_pkg_new(
"example.com", "helloworld", "0.1", "3.0", "noarch");
if (!pkg) {
fprintf(stderr, "%s\\n", strerror(ENOMEM));
return EXIT_FAILURE;
}
psys_pkg_add_summary(pkg, "C", "A simple Hello World program");
psys_pkg_add_description(pkg, "C",
"This is a simple program which prints "
"\\"Hello World\\" onto the screen. It is an "
"example of a program installed using the "
"psys library.");
if (psys_announce(pkg, &err)) {
fprintf(stderr, "psys_announce(): %s\\n", psys_err_msg(err));
psys_err_free(err);
psys_pkg_free(pkg);
return EXIT_FAILURE;
}
install();
if (psys_register(pkg, &err)) {
fprintf(stderr, "psys_register(): %s\\n", psys_err_msg(err));
psys_err_free(err);
psys_pkg_free(pkg);
return EXIT_FAILURE;
}
psys_pkg_free(pkg);
return EXIT_SUCCESS;
}
Psys is divided into two parts, a "frontend" and a "backend".
-
The frontend implements the distribution-independent functions of the psys library, e.g. for the creation of the psys data structures. This part is fully implemented by the psys library source code itself.
-
The backend is specific to a package manager or Linux distribution and implements the actual core functionality of the psys library interface (that is, processing notifications and package registration requests from installation programs). It can either be implemented by the package manager / distribution directly or, otherwise, by a fallback backend built into the core psys library itself. Currently, the psys library comes with fallback backends for RPM and Debian-based distributions; others may be added in the future. See
HACKINGfor general information about writing a psys library backend.
The availability of fallback backends means that the psys library can, in principal, be used on today's distros by installation programs which ship the library theirselves or statically link to it. As the psys library only takes care of the commmunication with the package manager, but leaves the actual installation / update / uninstallation to the installation program, adopting an existing installer to use the psys interface should require relatively little code modifications.
The psys library can be built like any autotools-powered project with
./configure [options]
make
make install # as super user (root, sudo)
In addition to the standard configure options, the following can be specified:
--enable-fallback-rpm Build RPM fallback backend (requires rpmlib)
--enable-fallback-dpkg Build DPKG fallback backend (requires libdpkg)
--enable-fallback-all Build all fallback backends
Note that in order to build the DPKG fallback backend, you need a
version of libdpkg.a which is compiled to position-independent code
with -fPIC; otherwise, linking will fail. As the libdpkg-dev
package in the Debian testing/unstable repositories is currently not
built with -fPIC, you need to build it yourself:
git clone git://git.debian.org/git/dpkg/dpkg.git
cd dpkg
## If you have a gettext version < 0.18 (e.g. Ubuntu 10.04): ##
git checkout 1.15.7
## Add -fPIC to compiler flags ##
echo "AM_CFLAGS += -fPIC" | cat lib/dpkg/Makefile.am - > Makefile.am.tmp
cp Makefile.am.tmp lib/dpkg/Makefile.am
rm Makefile.am.tmp
## Configure and install ##
autoreconf -i
./configure
cd lib/dpkg
make
sudo make install
Your dpkg installation will not be affected by this.
After having installed the psys library and a backend, you can test it by building and running the examples in the examples/ sub-directory:
cd examples/helloworld
make
sudo ./installer
sudo ./updater
sudo ./uninstaller
The psys library interface is documented in man page format; see the
sys(7) man page distributed with this library to get started.
Alternatively, all pages are available online at:
http://gitorious.org/libpsys/pages/ManPages
Also have a look at the examples in the examples/ sub-directory to
see the psys library in action (see Installation).
Contributions of any kind are, of course, very welcome! Please submit bug reports, patches, feature requests and branch merge requests to the libpsys newsgroup:
http://groups.google.com/group/libpsys
To track the development of the psys library and get the latest source code, visit the project page on Gitorious:
You are free to publish any number psys library branches there if you like.
For some information about hacking on the psys library source code, and a
short overview of writing psys library backends, see HACKING.