ostree: move admindir to /etc/alternatives.admindir

`ostree container commit` wipes /var and thereby erases the data in
/var/lib/alternatives; the directory used to store configs/symlinks of
alternatives.

/var is not a good place for storing such configs since it won't receive
updates on bootc images either.  We need to move to another location.

Hence, use /etc/alternatives.admindir when running on an ostree-based
system unless /var/lib/alternatives is already present; a user may have
worked around the problem.  This way we enable alternatives to work on
ostree-based systems without breaking backwards compat.

Fixes: #9
Signed-off-by: Valentin Rothberg <[email protected]>

Makefile

@@ -9,7 +9,7 @@ PROG = chkconfig
 BINDIR = /sbin
 SBINDIR = /usr/sbin
 MANDIR = /usr/man
-ALTDIR = /var/lib/alternatives
+LIBEXECDIR = /usr/libexec
 ALTDATADIR = /etc/alternatives
 SYSTEMDUTILDIR = $(shell pkg-config --variable=systemdutildir systemd)
 SUBDIRS = po
@@ -55,7 +55,6 @@ install:
 	[ -d $(DESTDIR)/$(SBINDIR) ] || mkdir -p $(DESTDIR)/$(SBINDIR)
 	[ -d $(DESTDIR)/$(MANDIR) ] || mkdir -p $(DESTDIR)/$(MANDIR)
 	[ -d $(DESTDIR)/$(MANDIR)/man8 ] || mkdir -p $(DESTDIR)/$(MANDIR)/man8
-	[ -d $(DESTDIR)/$(ALTDIR) ] || mkdir -p -m 755 $(DESTDIR)/$(ALTDIR)
 	[ -d $(DESTDIR)/$(ALTDATADIR) ] || mkdir -p -m 755 $(DESTDIR)/$(ALTDATADIR)
 	[ -d $(DESTDIR)/$(SYSTEMDUTILDIR) ] || mkdir -p -m 755 $(DESTDIR)/$(SYSTEMDUTILDIR)
 
@@ -66,6 +65,9 @@ install:
 	install -m 755 alternatives $(DESTDIR)/$(SBINDIR)/alternatives
 	ln -s alternatives $(DESTDIR)/$(SBINDIR)/update-alternatives
 
+	install -m 755 alternatives-migration $(DESTDIR)/$(LIBEXECDIR)/alternatives-migration
+	install -m systemd/alternatives-migration.service $(DESTDIR)/$(SYSTEMDUTILDIR)/system/alternatives-migration.service
+
 	for i in $(MAN); do \
 		install -m 644 $$i $(DESTDIR)/$(MANDIR)/man`echo $$i | sed "s/.*\.//"`/$$i ; \
 	done

alternatives-migration

@@ -0,0 +1,18 @@
+#!/usr/bin/sh
+
+# Already symlinked, nothing to do
+if [[ -L /var/lib/alternatives ]]; then
+    exit 0;
+fi
+
+# Make sure that the admindir exists
+mkdir -p /etc/alternatives.admindir
+
+# Migrate the contents
+if [[ -d /var/lib/alternatives ]]; then
+    mv /var/lib/alternatives/* /etc/alternatives.admindir
+    rm -r /var/lib/alternatives
+fi
+
+# Create the symlink
+ln -s /etc/alternatives.admindir /var/lib/alternatives

alternatives.8

@@ -210,10 +210,11 @@ containing the symlinks.
 .TP
 administrative directory
 A directory, by default
-.IR /var/lib/alternatives ,
+.IR /etc/alternatives.admindir ,
 containing
 .BR alternatives '
 state information.
+/var/lib/alternatives symlinks to it.
 .TP
 link group
 A set of related symlinks, intended to be updated as a group.
@@ -414,8 +415,9 @@ Can be overridden by the
 .B --altdir
 option.
 .TP
-.I /var/lib/alternatives/
+.I /etc/alternatives.admindir/
 The default administration directory.
+/var/lib/alternatives symlinks to it.
 Can be overridden by the
 .B --admindir
 option.

alternatives.c

@@ -1290,6 +1290,30 @@ static int listServices(const char *altDir, const char *stateDir, int flags) {
     return 0;
 }
 
+int dirExists(const char *path) {
+    struct stat sb;
+
+    if (stat(path, &sb) || !S_ISDIR(sb.st_mode) || access(path, F_OK)) {
+        if (errno == ENOENT) {
+            return 0;
+        }
+        fprintf(stderr, _("admindir %s invalid\n"), path);
+        exit(2);
+    }
+
+    return 1;
+}
+
+int canUseAlternativeAdminDirUnderOSTree() {
+    if (dirExists("/var/lib/alternatives")) { return 0; }
+
+    if (fileExists("/run/ostree-booted") || isLink("/ostree")) {
+        return 1;
+    }
+
+    return 0;
+}
+
 int main(int argc, const char **argv) {
     const char **nextArg;
     char *end;
@@ -1304,13 +1328,18 @@ int main(int argc, const char **argv) {
     struct stat sb;
     struct linkSet newSet = {NULL, NULL, NULL};
 
+    if (canUseAlternativeAdminDirUnderOSTree()) {
+        stateDir = "/etc/alternatives.admindir";
+    }
+
     setlocale(LC_ALL, "");
     bindtextdomain("chkconfig", "/usr/share/locale");
     textdomain("chkconfig");
 
     if (!argv[1])
         return usage(2);
 
+    int statedir_changed = 0;
     nextArg = argv + 1;
     while (*nextArg) {
         if (!strcmp(*nextArg, "--install")) {
@@ -1408,6 +1437,7 @@ int main(int argc, const char **argv) {
             altDir = normalize_path_alloc(*nextArg);
             nextArg++;
         } else if (!strcmp(*nextArg, "--admindir")) {
+            statedir_changed = 1;
             nextArg++;
             if (!*nextArg)
                 usage(2);
@@ -1428,6 +1458,13 @@ int main(int argc, const char **argv) {
         exit(2);
     }
 
+    if ((statedir_changed == 0) && (dirExists(stateDir) == 0)) {
+        if (mkdir(stateDir, 0755) == -1) {
+            fprintf(stderr, _("creating admindir: %s\n"), strerror(errno));
+            exit(2);
+        }
+    }
+
     if (stat(stateDir, &sb) || !S_ISDIR(sb.st_mode) || access(stateDir, F_OK)) {
         fprintf(stderr, _("admindir %s invalid\n"), stateDir);
         exit(2);

chkconfig.spec

@@ -6,7 +6,7 @@ License: GPL-2.0-only
 URL: https://github.com/fedora-sysv/chkconfig
 Source: https://github.com/fedora-sysv/chkconfig/archive/%{version}.tar.gz#/%{name}-%{version}.tar.gz
 
-BuildRequires: gcc gettext libselinux-devel make newt-devel popt-devel pkgconfig(systemd)
+BuildRequires: gcc gettext libselinux-devel make newt-devel popt-devel pkgconfig(systemd) systemd-rpm-macros
 # beakerlib might not be available on CentOS Stream any more
 %if 0%{?fedora}
 BuildRequires: beakerlib
@@ -93,11 +93,17 @@ mkdir -p $RPM_BUILD_ROOT/etc/chkconfig.d
 %files -n alternatives
 %license COPYING
 %dir /etc/alternatives
+%ghost /etc/alternatives.admindir
+%ghost /var/lib/alternatives
+%dir %{_libexecdir}/alternatives-migration
+%{_prefix}/lib/systemd/system/alternatives-migration.service
 %{_sbindir}/update-alternatives
 %{_sbindir}/alternatives
 %{_mandir}/*/update-alternatives*
 %{_mandir}/*/alternatives*
-%dir /var/lib/alternatives
+
+%postun
+%systemd_postun alternatives-migration.service
 
 %changelog
 * Fri Jun 21 2024 Jan Macku <[email protected]> - 1.28-1

po/chkconfig.pot

@@ -8,7 +8,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: PACKAGE VERSION\n"
 "Report-Msgid-Bugs-To: \n"
-"POT-Creation-Date: 2024-07-26 11:46+0200\n"
+"POT-Creation-Date: 2024-07-30 14:56+0200\n"
 "PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n"
 "Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
 "Language-Team: LANGUAGE <[email protected]>\n"
@@ -562,22 +562,27 @@ msgstr ""
 msgid "failed to remove %s: %s\n"
 msgstr ""
 
-#: ../alternatives.c:1365
+#: ../alternatives.c:1300 ../alternatives.c:1469
+#, c-format
+msgid "admindir %s invalid\n"
+msgstr ""
+
+#: ../alternatives.c:1394
 #, c-format
 msgid "--family can't contain the symbol '@'\n"
 msgstr ""
 
-#: ../alternatives.c:1427
+#: ../alternatives.c:1457
 #, c-format
 msgid "altdir %s invalid\n"
 msgstr ""
 
-#: ../alternatives.c:1432
+#: ../alternatives.c:1463
 #, c-format
-msgid "admindir %s invalid\n"
+msgid "creating admindir: %s\n"
 msgstr ""
 
-#: ../alternatives.c:1442
+#: ../alternatives.c:1479
 #, c-format
 msgid "alternatives version %s\n"
 msgstr ""

systemd/alternatives-migration.service

@@ -0,0 +1,18 @@
+[Unit]
+Description=Migrate /var/lib/alternatives to /etc/alternatives.admindir
+Documentation=man:alternatives(8)
+
+# This should run before any other daemons/tools that may use alternatives
+DefaultDependencies=no
+After=sysinit.target
+Before=basic.target shutdown.target
+Conflicts=shutdown.target
+# In case /var is remote-mounted
+RequiresMountsFor=/var
+
+[Service]
+Type=oneshot
+ExecStart=/usr/libexec/alternatives-migration
+
+[Install]
+WantedBy=default.target