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

20 files changed, 111 insertions, 63 deletions

diff --git a/hwdb.d/meson.build b/hwdb.d/meson.build
index 63a56b49cc..6fcb364acd 100644
--- a/hwdb.d/meson.build
+++ b/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')
diff --git a/meson.build b/meson.build
index 19efa92db8..7996bc2c65 100644
--- a/meson.build
+++ b/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',
diff --git a/meson_options.txt b/meson_options.txt
index ff45d60350..2435ccebd4 100644
--- a/meson_options.txt
+++ b/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')
diff --git a/network/meson.build b/network/meson.build
index 08f29ca7df..b0e60f7217 100644
--- a/network/meson.build
+++ b/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',
diff --git a/src/core/meson.build b/src/core/meson.build
index 552590393d..77767eb603 100644
--- a/src/core/meson.build
+++ b/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
diff --git a/src/coredump/meson.build b/src/coredump/meson.build
index 663c6c7a07..ebd99bd379 100644
--- a/src/coredump/meson.build
+++ b/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
diff --git a/src/home/meson.build b/src/home/meson.build
index 7847449c43..e3cc1a9fb5 100644
--- a/src/home/meson.build
+++ b/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 += [
diff --git a/src/journal-remote/meson.build b/src/journal-remote/meson.build
index 66cbcc69df..4572f4bd1c 100644
--- a/src/journal-remote/meson.build
+++ b/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'))
diff --git a/src/journal/meson.build b/src/journal/meson.build
index 520e33c0b8..7aea28d129 100644
--- a/src/journal/meson.build
+++ b/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(
diff --git a/src/kernel-install/meson.build b/src/kernel-install/meson.build
index 851e827590..4117188f14 100644
--- a/src/kernel-install/meson.build
+++ b/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
diff --git a/src/login/meson.build b/src/login/meson.build
index fd3202cd98..e09610960b 100644
--- a/src/login/meson.build
+++ b/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)
diff --git a/src/network/meson.build b/src/network/meson.build
index cd1a897199..f5ca183088 100644
--- a/src/network/meson.build
+++ b/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',
diff --git a/src/oom/meson.build b/src/oom/meson.build
index a250d2a62a..e966ad1dd8 100644
--- a/src/oom/meson.build
+++ b/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
diff --git a/src/pstore/meson.build b/src/pstore/meson.build
index 3b3a37c777..6c0ab0563b 100644
--- a/src/pstore/meson.build
+++ b/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
diff --git a/src/resolve/meson.build b/src/resolve/meson.build
index eb6fabea95..8e7bad0659 100644
--- a/src/resolve/meson.build
+++ b/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)
diff --git a/src/timesync/meson.build b/src/timesync/meson.build
index 22b6347bab..571e3fc7ef 100644
--- a/src/timesync/meson.build
+++ b/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',
diff --git a/src/udev/meson.build b/src/udev/meson.build
index e6dd4c7cac..5eb0f994a5 100644
--- a/src/udev/meson.build
+++ b/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',
diff --git a/sysctl.d/meson.build b/sysctl.d/meson.build
index e9b20ea540..e8d8fc8c53 100644
--- a/sysctl.d/meson.build
+++ b/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
diff --git a/tmpfiles.d/meson.build b/tmpfiles.d/meson.build
index a41dd3e454..7322460dba 100644
--- a/tmpfiles.d/meson.build
+++ b/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')))
diff --git a/units/meson.build b/units/meson.build
index e249539dc8..ba60eb7fc1 100644
--- a/units/meson.build
+++ b/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'))