Scriptlets

RPM spec files have several sections which allow packages to run code on installation and removal. These bits of code are called scriptlets and are mostly used to update the running system with information from the package. This page offers a quick overview of RPM scriptlets and a number of common recipes for scriptlets in packages. For a more complete treatment of scriptlets, please see the Maximum RPM book.

The version of RPM in Fedora also has functionality to automatically run scripts when files are placed in certain locations. (See 1.) This potentially obviates the need for most of the scriptlets on this page, but is not currently implemented in all cases where it could be.

Default Shell

In Fedora, all scriptlets can safely assume they are running under the bash shell unless a different language has been specified.

Syntax

The basic syntax is similar to the %build, %install, and other sections of the rpm spec file. The scripts support a special flag, -p which allows the scriptlet to invoke a single program directly rather than having to spawn a shell to invoke the programs. (i.e., %post -p /sbin/ldconfig)

When scriptlets are called, they will be supplied with an argument. This argument, accessed via $1 (for shell scripts) is the number of packages of this name which will be left on the system when the action completes. So for the common case of install, upgrade, and uninstall we have:

install

upgrade

uninstall

%pretrans

$1 == 1

$1 == 2

(N/A)

%pre

$1 == 1

$1 == 2

(N/A)

%post

$1 == 1

$1 == 2

(N/A)

%preun

(N/A)

$1 == 1

$1 == 0

%postun

(N/A)

$1 == 1

$1 == 0

%posttrans

$1 == 1

$1 == 1

(N/A)

Note that these values will vary if there are multiple versions of the same package installed (This mostly occurs with parallel installable packages such as the kernel and multilib packages. However, it can also occur when errors prevent a package upgrade from completing.) So it is a good idea to use this construct:

%pre
if [ $1 -gt 1 ] ; then
fi

for %pre and %post scripts rather than checking that it equals 2.

All scriptlets MUST exit with the zero exit status. Because RPM in its default configuration does not execute shell scriptlets with the -e argument to the shell, excluding explicit exit calls (frowned upon with a non-zero argument!), the exit status of the last command in a scriptlet determines its exit status. Most commands in the snippets in this document have a “|| :” appended to them, which is a generic trick to force the zero exit status for those commands whether they worked or not. Usually the most important bit is to apply this to the last command executed in a scriptlet, or to add a separate command such as plain “:” or “exit 0” as the last one in a scriptlet. Note that depending on the case, other error checking/prevention measures may be more appropriate.

Non-zero exit codes from scriptlets can break installs/upgrades/erases such that no further actions will be taken for that package in a transaction (see Ordering), which may for example prevent an old version of a package from being erased on upgrades, leaving behind duplicate rpmdb entries and possibly stale, unowned files on the filesystem. There are some cases where letting the transaction to proceed when some things in scriptlets failed may result in partially broken setup. It is however often limited to that package only whereas letting a transaction to proceed with some packages dropped out on the fly is more likely to result in broader system wide problems.

Ordering

The scriptlets in %pre and %post are respectively run before and after a package is installed. The scriptlets %preun and %postun are run before and after a package is uninstalled. The scriptlets %pretrans and %posttrans are run at start and end of a transaction. On upgrade, the scripts are run in the following order:

  1. %pretrans of new package

  2. %pre of new package

  3. (package install)

  4. %post of new package

  5. %triggerin of other packages (set off by installing new package)

  6. %triggerin of new package (if any are true)

  7. %triggerun of old package (if it’s set off by uninstalling the old package)

  8. %triggerun of other packages (set off by uninstalling old package)

  9. %preun of old package

  10. (removal of old package)

  11. %postun of old package

  12. %triggerpostun of old package (if it’s set off by uninstalling the old package)

  13. %triggerpostun of other packages (if they’re set off by uninstalling the old package)

  14. %posttrans of new package

The %pretrans Scriptlet

Note that the %pretrans scriptlet will, in the particular case of system installation, run before anything at all has been installed. This implies that it cannot have any dependencies at all. For this reason, %pretrans is best avoided, but if used it MUST (by necessity) be written in Lua. See https://rpm-software-management.github.io/rpm/manual/lua.html for more information.

Writing Scriptlets

Here are some tips for writing good scriptlets:

Saving state between scriptlets

Sometimes a scriptlet needs to save some state from an earlier running scriptlet in order to use it at a later running scriptlet. This is especially common when trying to optimize the scriptlets. Examples:

  • If a %posttrans needs to de-register some piece of information when upgrading but the file that has that information is removed when the old package is removed the scriptlets need to save that file during %pre or %post so that the script in %posttrans can access it.

  • If we only want the program in %posttrans to do its work once per-transaction, we may need to write out a flag file so that the %posttrans knows whether to perform an action.

To address these issues scriptlets that run earlier need to write out information that is used in %posttrans. We recommend using a subdirectory of %{_localstatedir}/lib/rpm-state/ for that. For instance, the eclipse plugin scripts touch a file in %{_localstatedir}/lib/rpm-state/eclipse/ when they’re installed. The %posttrans runs a script that checks if that file exists. If it does, it performs its action and then deletes the file. That way the script only performs its action once per transaction.

Macros

If RPM file triggers are not appropriate, complex scriptlets which are shared between multiple packages MAY be placed in RPM macros. This has two benefits:

  • The standard package authors only have to remember the macros, not the complex stuff that it does

  • The macros' implementations may change without having to update the package

When writing the macros, the FPC will still want to review the macros (and perhaps include the implementation of the macros in the guideline to show packagers what’s happening behind the scenes).

One principle that the FPC follows is that macros generally don’t contain the start of scriptlet tags (for instance, %pre) because this makes it difficult to do additional work in the scriptlet. This also means that a single macro can not be defined to do things in both %pre and %post. Instead, write one macro that performs the actions in %pre and a separate macro that performs the actions in %post. This principle makes it so that all spec files can use your macros in the same manner even if they already have a %pre or %post defined.

Of course, in the above situation it is better to use RPM file triggers if at all possible.

Snippets

Some scriptlets to use in specific situations.

Linker Configuration Files

Packages which place linker configuration files in /etc/ld.so.conf.d MUST call ldconfig in %post and %postun (on all Fedora releases) even if they install no actual libraries. They MUST NOT use the %ldconfig, %ldconfig_post, %ldconfig_postun or %ldconfig_scriptlets macros to do this, since these macros do not have any effect on Fedora. Instead simply call /sbin/ldconfig directly in both %post and %postun as well as adding the necessary dependencies when necessary:

%post -p /sbin/ldconfig
%postun -p /sbin/ldconfig

or, as part of existing %post or %postun scriptlets:

Requires(post): /sbin/ldconfig
Requires(postun): /sbin/ldconfig
[...]
%post
[...]
/sbin/ldconfig
[...]
%postun
[...]
/sbin/ldconfig
[...]

If the configuration file added to /etc/ld.so.conf.d specifies a directory into which other packages may install files, and that directory is not located in the directory hierarchy beneath one of /lib, /usr/lib, /lib64 or /usr/lib64, then the package adding the configuration file MUST also include the following file triggers which cause ldconfig to be run automatically when necessary:

%transfiletriggerin -P 2000000 -- DIRECTORIES
/sbin/ldconfig

%transfiletriggerpostun -P 2000000 -- DIRECTORIES
/sbin/ldconfig

Replace DIRECTORIES with the space-separated list of directories which the package adds to the library search path via the configuration files in /etc/ld.so.conf.d.

Users and groups

These are discussed on a separate page.

GConf

GConf is a configuration scheme currently used by the GNOME desktop. Programs which use it setup default values in a .schemas file which is installed under %{_sysconfdir}/gconf/schemas/[NAME].schemas. These defaults are then registered with the gconf daemon which monitors the configuration values and alerts applications when values the applications are interested in change. The schema files also provide documentation about what each value in the configuration system means (which gets displayed when you browse the database in the gconf-editor program).

For packaging purposes, we have to disable schema installation during build, and also register the values in the [NAME].schemas file with the gconf daemon on installation and unregister them on removal. Due to the ordering of the scriptlets, this is a four step process.

Disabling the GConf installation during the package creation can be done like so:

%install
export GCONF_DISABLE_MAKEFILE_SCHEMA_INSTALL=1
make install DESTDIR=$RPM_BUILD_ROOT
...

The GCONF_DISABLE_MAKEFILE_SCHEMA_INSTALL environment variable suppresses the installation of the schema during the building of the package. An alternative for some packages is to pass a configure flag:

%build
%configure --disable-schemas
...

Unfortunately, this configure switch only works if the upstream packager has adapted their Makefile.am file to handle it. If the Makefile.am file is not configured, this switch won’t do anything and you’ll need to use the environment variable instead.

Here’s the second part:

BuildRequires: GConf2
Requires(pre): GConf2
Requires(post): GConf2
Requires(preun): GConf2
...
%pre
%gconf_schema_prepare schema1 schema2
%gconf_schema_obsolete schema3

In this section we uninstall old schemas during upgrade using one of two macros.

%gconf_schema_prepare is used for any current GConf schemas. It takes care of uninstalling previous versions of schemas that this package currently installs. It takes a space separated list of schema names without path or suffix that the package installs. Note that behind the scenes, this macro works with the %post scriptlet to only process GConf schemas if changes have occurred.

%gconf_schema_obsolete is used for schemas that this package previously provided but no longer does. It will deregister the old schema if it is present on the system. Nothing will happen if the old schema is not present. This macro takes a space separated list of schemas to uninstall. One example of using this might be if the package changed names. If the old schema was named foo.schemas and the new schema is named foobar.schemas you’d use:

%gconf_schema_prepare foobar
%gconf_schema_obsolete foo

The next section does the processing of the newly installed schemas:

%post
%gconf_schema_upgrade schema1 schema2

%gconf_schema_upgrade takes a space separated list of schemas that the package currently installs just like %gconf_schema_prepare. Behind the scenes, it does the actual work of registering the new version of the schema and deregistering the old version.

The last section is for unregistering schemas when a package is removed:

%preun
%gconf_schema_remove schema1 schema2

When a package is upgraded rpm invokes the %pre scriptlet to register and deregister the schemas. When a package is uninstalled, the %preun scriptlet is used. %gconf_schema_remove takes the list of schemas that this package currently provides and removes them for us.

Rebuilds for changes to macros

When macros change, packages that make use of them have to be rebuilt to pick up the changes. This repoquery command can be used to find the schema including packages to rebuild:

repoquery --whatprovides "/etc/gconf/schemas/*" |sort |uniq |wc -l

Systemd

Packages containing systemd unit files need to use scriptlets to ensure proper handling of those services. Services can either be enabled or disabled by default. To determine which case your specific service falls into, please refer to FESCo’s policy here. On upgrade, a package may only restart a service if it is running; it may not start it if it is off. Also, the service may not enable itself if it is currently disabled.

Scriptlets

The systemd package provides a set of helper macros to handle systemd scriptlet operations. These macros support systemd "presets", as documented in systemd.preset(5).

BuildRequires: systemd-rpm-macros

[...]
%post
%systemd_post apache-httpd.service

%preun
%systemd_preun apache-httpd.service

%postun
%systemd_postun_with_restart apache-httpd.service

Some services do not support being restarted (e.g. D-Bus and various storage daemons). If your service should not be restarted upon upgrade, then use the following %postun scriptlet instead of the one shown above:

%postun
%systemd_postun apache-httpd.service

If your package includes one or more systemd units that need to be enabled by default on package installation, they MUST be covered by the Fedora preset policy.

User units

There are additional macros for user units (those installed under %_userunitdir) that should be used similarly to those for system units. These enable and disable user units according to presets, and are %systemd_user_post (to be used in %post) and %systemd_user_preun (to be used in %preun).

BuildRequires: systemd-rpm-macros

[...]
%post
%systemd_user_post %{name}.service

%preun
%systemd_user_preun %{name}.service
Dependencies on the systemd package

If package scriptlets call other systemd tools, for example systemd-tmpfiles, the package SHOULD declare appropriate dependencies. The %{?systemd_requires} macro is a shortcut to require systemd for the %pre, %post, and %postun scriptlets. Note that those dependencies are not required for the %systemd_{post,preun,postun_with_restart,user_post,user_preun} macros listed above.

If the package wants to use systemd tools if they are available, but does not want to declare a dependency, then the %{?systemd_ordering} macro MAY be used as a weaker form of %{?systemd_requires} that only declares an ordering during an RPM transaction.

The macros take the form %{?systemd_requires} instead of %systemd_requires to allow the specfile to parse properly in the case where the systemd macros have yet to be installed.
Macro details

For details on what these macros evaluate to, refer to the following sources: macros.systemd.in, triggers.systemd.in and daemon(7).

Shells

/etc/shells is a text file which controls whether an application can be used as a system login shell of users. It contains the set of valid shells which can be used in the system. If you are packaging a new shell, you need to add entries to this file that reference the added shells. See: man 5 SHELLS for more information.

As this file can be edited by sysadmins, we need to first determine if relevant lines are already in the file. If they don’t already exist then we just need to echo the shell’s binary path to the file. Since the UsrMove Feature in Fedora 17 made /bin a symlink to /usr/bin we need to place both paths into the /etc/shells file. Here is an example of the scriptlet to package with shell named "foo":

%post
if [ "$1" = 1 ]; then
  if [ ! -f %{_sysconfdir}/shells ] ; then
    echo "%{_bindir}/foo" > %{_sysconfdir}/shells
    echo "/bin/foo" >> %{_sysconfdir}/shells
  else
    grep -q "^%{_bindir}/foo$" %{_sysconfdir}/shells || echo "%{_bindir}/foo" >> %{_sysconfdir}/shells
    grep -q "^/bin/foo$" %{_sysconfdir}/shells || echo "/bin/foo" >> %{_sysconfdir}/shells
fi

%postun
if [ "$1" = 0 ] && [ -f %{_sysconfdir}/shells ] ; then
  sed -i '\!^%{_bindir}/foo$!d' %{_sysconfdir}/shells
  sed -i '\!^/bin/foo$!d' %{_sysconfdir}/shells
fi