meson: add option to skip installing to $sysconfdir

This is useful for development where overwriting files out side
the configured prefix will affect the host as well as stateless
systems such as NixOS that don't let packages install to /etc but handle
configuration on their own.

Alternative to https://github.com/systemd/systemd/pull/17501

tested with:

$ mkdir inst build && cd build
$ meson \
  -Dcreate-log-dirs=false \
  -Dsysvrcnd-path=$(realpath ../inst)/etc/rc.d \
  -Dsysvinit-path=$(realpath ../inst)/etc/init.d \
  -Drootprefix=$(realpath ../inst) \
  -Dinstall-sysconfdir=false \
  --prefix=$(realpath ../inst) ..
$ ninja install

hwdb.d/meson.build

@@ -42,12 +42,14 @@ if conf.get('ENABLE_HWDB') == 1
                      hwdb_files_test,
                      install_dir : udevhwdbdir)
 
-        meson.add_install_script('sh', '-c',
-                                 mkdir_p.format(join_paths(sysconfdir, 'udev/hwdb.d')))
+        if install_sysconfdir
+                meson.add_install_script('sh', '-c',
+                                         mkdir_p.format(join_paths(sysconfdir, 'udev/hwdb.d')))
 
-        meson.add_install_script('sh', '-c',
-                                 'test -n "$DESTDIR" || @0@/systemd-hwdb update'
-                                 .format(rootbindir))
+                meson.add_install_script('sh', '-c',
+                                         'test -n "$DESTDIR" || @0@/systemd-hwdb update'
+                                         .format(rootbindir))
+        endif
 
         if want_tests != 'false'
                 parse_hwdb_py = find_program('parse_hwdb.py')

meson.build

@@ -126,6 +126,7 @@ if rootlibdir == ''
         rootlibdir = join_paths(rootprefixdir, libdir.split('/')[-1])
 endif
 
+install_sysconfdir = get_option('install-sysconfdir')
 # Dirs of external packages
 pkgconfigdatadir = get_option('pkgconfigdatadir') == '' ? join_paths(datadir, 'pkgconfig') : get_option('pkgconfigdatadir')
 pkgconfiglibdir = get_option('pkgconfiglibdir') == '' ? join_paths(libdir, 'pkgconfig') : get_option('pkgconfiglibdir')
@@ -2776,8 +2777,10 @@ if conf.get('ENABLE_BINFMT') == 1
 
         meson.add_install_script('sh', '-c',
                                  mkdir_p.format(binfmtdir))
-        meson.add_install_script('sh', '-c',
-                                 mkdir_p.format(join_paths(sysconfdir, 'binfmt.d')))
+        if install_sysconfdir
+                meson.add_install_script('sh', '-c',
+                                         mkdir_p.format(join_paths(sysconfdir, 'binfmt.d')))
+        endif
 endif
 
 if conf.get('ENABLE_REPART') == 1
@@ -2891,8 +2894,10 @@ executable(
         install : true,
         install_dir : rootlibexecdir)
 
-install_data('src/sleep/sleep.conf',
-             install_dir : pkgsysconfdir)
+if install_sysconfdir
+        install_data('src/sleep/sleep.conf',
+                     install_dir : pkgsysconfdir)
+endif
 
 public_programs += executable(
         'systemd-sysctl',
@@ -3243,8 +3248,10 @@ if conf.get('HAVE_KMOD') == 1
 
         meson.add_install_script('sh', '-c',
                                  mkdir_p.format(modulesloaddir))
-        meson.add_install_script('sh', '-c',
-                                 mkdir_p.format(join_paths(sysconfdir, 'modules-load.d')))
+        if install_sysconfdir
+                meson.add_install_script('sh', '-c',
+                                         mkdir_p.format(join_paths(sysconfdir, 'modules-load.d')))
+        endif
 endif
 
 public_programs += executable(
@@ -3489,8 +3496,10 @@ subdir('docs/var-log')
 install_subdir('factory/etc',
                install_dir : factorydir)
 
-install_data('xorg/50-systemd-user.sh',
-             install_dir : xinitrcdir)
+if install_sysconfdir
+        install_data('xorg/50-systemd-user.sh',
+                     install_dir : xinitrcdir)
+endif
 install_data('modprobe.d/systemd.conf',
              install_dir : modprobedir)
 install_data('LICENSE.GPL2',

meson_options.txt

@@ -180,6 +180,8 @@ option('pamconfdir', type : 'string',
        description : 'directory for PAM configuration ["no" disables]')
 option('docdir', type : 'string',
        description : 'documentation directory')
+option('install-sysconfdir', type : 'boolean', value : true,
+       description : 'install configuration files to $sysconfdir')
 
 option('fallback-hostname', type : 'string', value : 'localhost',
        description : 'the hostname used if none configured')

network/meson.build

@@ -10,8 +10,10 @@ if conf.get('ENABLE_NETWORKD') == 1
                      '80-wifi-station.network.example',
                      install_dir : networkdir)
 
-        meson.add_install_script('sh', '-c',
-                                 mkdir_p.format(join_paths(sysconfdir, 'systemd/network')))
+        if install_sysconfdir
+                meson.add_install_script('sh', '-c',
+                                         mkdir_p.format(join_paths(sysconfdir, 'systemd/network')))
+        endif
 endif
 
 install_data('99-default.link',

src/core/meson.build

@@ -192,12 +192,14 @@ in_files = [['macros.systemd',   rpmmacrosdir],
 foreach item : in_files
         file = item[0]
         dir = item[1]
+        if install_sysconfdir or dir != pkgsysconfdir
+                configure_file(
+                        input : file + '.in',
+                        output : file,
+                        configuration : substs,
+                        install_dir : dir == 'no' ? '' : dir)
+        endif
 
-        configure_file(
-                input : file + '.in',
-                output : file,
-                configuration : substs,
-                install_dir : dir == 'no' ? '' : dir)
 endforeach
 
 install_data('org.freedesktop.systemd1.conf',
@@ -217,6 +219,8 @@ meson.add_install_script('sh', '-c', mkdir_p.format(systemsleepdir))
 meson.add_install_script('sh', '-c', mkdir_p.format(systemgeneratordir))
 meson.add_install_script('sh', '-c', mkdir_p.format(usergeneratordir))
 
-meson.add_install_script('sh', '-c', mkdir_p.format(join_paths(pkgsysconfdir, 'system')))
-meson.add_install_script('sh', '-c', mkdir_p.format(join_paths(pkgsysconfdir, 'user')))
-meson.add_install_script('sh', '-c', mkdir_p.format(join_paths(sysconfdir, 'xdg/systemd')))
+if install_sysconfdir
+        meson.add_install_script('sh', '-c', mkdir_p.format(join_paths(pkgsysconfdir, 'system')))
+        meson.add_install_script('sh', '-c', mkdir_p.format(join_paths(pkgsysconfdir, 'user')))
+        meson.add_install_script('sh', '-c', mkdir_p.format(join_paths(sysconfdir, 'xdg/systemd')))
+endif

src/coredump/meson.build

@@ -13,7 +13,7 @@ endif
 
 coredumpctl_sources = files('coredumpctl.c')
 
-if conf.get('ENABLE_COREDUMP') == 1
+if conf.get('ENABLE_COREDUMP') == 1 and install_sysconfdir
         install_data('coredump.conf',
                      install_dir : pkgsysconfdir)
 endif

src/home/meson.build

@@ -107,8 +107,10 @@ if conf.get('ENABLE_HOMED') == 1
         install_data('org.freedesktop.home1.policy',
                      install_dir : polkitpolicydir)
 
-        install_data('homed.conf',
-                     install_dir : pkgsysconfdir)
+        if install_sysconfdir
+                install_data('homed.conf',
+                             install_dir : sysconfdir)
+        endif
 endif
 
 tests += [

src/journal-remote/meson.build

@@ -48,8 +48,10 @@ if conf.get('ENABLE_REMOTE') ==1 and conf.get('HAVE_LIBCURL') == 1
                 input : 'journal-upload.conf.in',
                 output : 'journal-upload.conf',
                 configuration : substs)
-        install_data(journal_upload_conf,
-                     install_dir : pkgsysconfdir)
+        if install_sysconfdir
+                install_data(journal_upload_conf,
+                             install_dir : pkgsysconfdir)
+        endif
 endif
 
 if conf.get('ENABLE_REMOTE') == 1 and conf.get('HAVE_MICROHTTPD') == 1
@@ -57,8 +59,10 @@ if conf.get('ENABLE_REMOTE') == 1 and conf.get('HAVE_MICROHTTPD') == 1
                 input : 'journal-remote.conf.in',
                 output : 'journal-remote.conf',
                 configuration : substs)
-        install_data(journal_remote_conf,
-                     install_dir : pkgsysconfdir)
+        if install_sysconfdir
+                install_data(journal_remote_conf,
+                             install_dir : pkgsysconfdir)
+        endif
 
         install_data('browse.html',
                      install_dir : join_paths(pkgdatadir, 'gatewayd'))

src/journal/meson.build

@@ -107,8 +107,10 @@ journalctl_sources = files('''
         pcre2-dlopen.h
 '''.split())
 
-install_data('journald.conf',
-             install_dir : pkgsysconfdir)
+if install_sysconfdir
+        install_data('journald.conf',
+                     install_dir : pkgsysconfdir)
+endif
 
 if get_option('create-log-dirs')
         meson.add_install_script(

src/kernel-install/meson.build

@@ -3,16 +3,19 @@
 want_kernel_install = get_option('kernel-install')
 
 if want_kernel_install
-	install_data('kernel-install',
-		install_mode : 'rwxr-xr-x',
-		install_dir : bindir)
+        install_data('kernel-install',
+                     install_mode : 'rwxr-xr-x',
+                     install_dir : bindir)
 
-	install_data('00-entry-directory.install',
-		'50-depmod.install',
-		'90-loaderentry.install',
-		install_mode : 'rwxr-xr-x',
-		install_dir : kernelinstalldir)
+        install_data('00-entry-directory.install',
+                     '50-depmod.install',
+                     '90-loaderentry.install',
+                     install_mode : 'rwxr-xr-x',
+                     install_dir : kernelinstalldir)
+
+        if install_sysconfdir
+                meson.add_install_script('sh', '-c',
+                                         mkdir_p.format(join_paths(sysconfdir, 'kernel/install.d')))
+        endif
 
-	meson.add_install_script('sh', '-c',
-				mkdir_p.format(join_paths(sysconfdir, 'kernel/install.d')))
 endif

src/login/meson.build

@@ -74,8 +74,10 @@ if conf.get('ENABLE_LOGIND') == 1
                 input : 'logind.conf.in',
                 output : 'logind.conf',
                 configuration : substs)
-        install_data(logind_conf,
-                     install_dir : pkgsysconfdir)
+        if install_sysconfdir
+                install_data(logind_conf,
+                             install_dir : pkgsysconfdir)
+        endif
 
         install_data('org.freedesktop.login1.conf',
                      install_dir : dbuspolicydir)

src/network/meson.build

@@ -236,8 +236,10 @@ if conf.get('ENABLE_NETWORKD') == 1
                              install_dir : polkitpkladir)
         endif
 
-        install_data('networkd.conf',
-                     install_dir : pkgsysconfdir)
+        if install_sysconfdir
+                install_data('networkd.conf',
+                             install_dir : pkgsysconfdir)
+        endif
 
         fuzzers += [
     [['src/network/fuzz-netdev-parser.c',

src/oom/meson.build

@@ -29,6 +29,8 @@ if conf.get('ENABLE_OOMD') == 1
         install_data('org.freedesktop.oom1.service',
                      install_dir : dbussystemservicedir)
 
-        install_data('oomd.conf',
-                     install_dir : pkgsysconfdir)
+        if install_sysconfdir
+                install_data('oomd.conf',
+                             install_dir : sysconfdir)
+        endif
 endif

src/pstore/meson.build

@@ -4,7 +4,7 @@ systemd_pstore_sources = files('''
         pstore.c
 '''.split())
 
-if conf.get('ENABLE_PSTORE') == 1
+if conf.get('ENABLE_PSTORE') == 1 and install_sysconfdir
         install_data('pstore.conf',
                      install_dir : pkgsysconfdir)
 endif

src/resolve/meson.build

@@ -169,8 +169,10 @@ if conf.get('ENABLE_RESOLVE') == 1
                 input : 'resolved.conf.in',
                 output : 'resolved.conf',
                 configuration : substs)
-        install_data(resolved_conf,
-                     install_dir : pkgsysconfdir)
+        if install_sysconfdir
+                install_data(resolved_conf,
+                             install_dir : pkgsysconfdir)
+        endif
 
         install_data('resolv.conf',
                      install_dir : rootlibexecdir)

src/timesync/meson.build

@@ -26,8 +26,10 @@ if conf.get('ENABLE_TIMESYNCD') == 1
                 input : 'timesyncd.conf.in',
                 output : 'timesyncd.conf',
                 configuration : substs)
-        install_data(timesyncd_conf,
-                     install_dir : pkgsysconfdir)
+        if install_sysconfdir
+                install_data(timesyncd_conf,
+                             install_dir : pkgsysconfdir)
+        endif
         install_data('org.freedesktop.timesync1.conf',
                      install_dir : dbuspolicydir)
         install_data('org.freedesktop.timesync1.service',

src/udev/meson.build

@@ -185,8 +185,10 @@ foreach prog : [['ata_id/ata_id.c'],
                    install_dir : udevlibexecdir)
 endforeach
 
-install_data('udev.conf',
-             install_dir : join_paths(sysconfdir, 'udev'))
+if install_sysconfdir
+        install_data('udev.conf',
+                     install_dir : join_paths(sysconfdir, 'udev'))
+endif
 
 configure_file(
         input : 'udev.pc.in',
@@ -194,8 +196,10 @@ configure_file(
         configuration : substs,
         install_dir : pkgconfigdatadir == 'no' ? '' : pkgconfigdatadir)
 
-meson.add_install_script('sh', '-c',
-                         mkdir_p.format(join_paths(sysconfdir, 'udev/rules.d')))
+if install_sysconfdir
+        meson.add_install_script('sh', '-c',
+                                 mkdir_p.format(join_paths(sysconfdir, 'udev/rules.d')))
+endif
 
 fuzzers += [
         [['src/udev/net/fuzz-link-parser.c',

sysctl.d/meson.build

@@ -26,5 +26,7 @@ foreach file : in_files
                      install_dir : sysctldir)
 endforeach
 
-meson.add_install_script('sh', '-c',
-                         mkdir_p.format(join_paths(sysconfdir, 'sysctl.d')))
+if install_sysconfdir
+        meson.add_install_script('sh', '-c',
+                                 mkdir_p.format(join_paths(sysconfdir, 'sysctl.d')))
+endif

tmpfiles.d/meson.build

@@ -55,7 +55,7 @@ foreach file : m4_files
         endif
 endforeach
 
-if enable_tmpfiles
+if enable_tmpfiles and install_sysconfdir
         meson.add_install_script(
                 'sh', '-c',
                 mkdir_p.format(join_paths(sysconfdir, 'tmpfiles.d')))

units/meson.build

@@ -326,9 +326,11 @@ install_data('user-.slice.d/10-defaults.conf',
 
 ############################################################
 
-meson.add_install_script(meson_make_symlink,
-                         join_paths(pkgsysconfdir, 'user'),
-                         join_paths(sysconfdir, 'xdg/systemd/user'))
+if install_sysconfdir
+        meson.add_install_script(meson_make_symlink,
+                                 join_paths(pkgsysconfdir, 'user'),
+                                 join_paths(sysconfdir, 'xdg/systemd/user'))
+endif
 meson.add_install_script(meson_make_symlink,
                          join_paths(dbussystemservicedir, 'org.freedesktop.systemd1.service'),
                          join_paths(dbussessionservicedir, 'org.freedesktop.systemd1.service'))