Allow system.devices to be automatically created on first boot

An OS installer can create system.devices for the system and
disks, but an OS image cannot create the system-specific
system.devices.  The OS image can instead configure the
image so that lvm will create system.devices on first boot.

Image preparation steps to enable auto creation of system.devices:
- create empty file /etc/lvm/devices/auto-import-rootvg
- remove any existing /etc/lvm/devices/system.devices
- enable lvm-devices-import.path
- enable lvm-devices-import.service

On first boot of the prepared image:
- udev triggers vgchange -aay --autoactivation event <rootvg>
- vgchange activates LVs in the root VG
- vgchange finds the file /etc/lvm/devices/auto-import-rootvg,
  and no /etc/lvm/devices/system.devices, so it creates
  /run/lvm/lvm-devices-import
- lvm-devices-import.path is run when /run/lvm/lvm-devices-import
  appears, and triggers lvm-devices-import.service
- lvm-devices-import.service runs vgimportdevices --rootvg --auto
- vgimportdevices finds /etc/lvm/devices/auto-import-rootvg,
  and no system.devices, so it creates system.devices containing
  PVs in the root VG, and removes /etc/lvm/devices/auto-import-rootvg
  and /run/lvm/lvm-devices-import

Run directly, vgimportdevices --rootvg (without --auto), will create
a new system.devices for the root VG, or will add devices for the
root VG to an existing system.devices.

lib/commands/toolcontext.h

@@ -217,6 +217,7 @@ struct cmd_context {
 	unsigned device_ids_check_hostname:1;
 	unsigned device_ids_refresh_trigger:1;
 	unsigned device_ids_invalid:1;
+	unsigned device_ids_auto_import:1;
 	unsigned get_vgname_from_options:1;     /* used by lvconvert */
 
 	/*

lib/config/defaults.h

@@ -337,6 +337,8 @@
 #define VGS_ONLINE_DIR DEFAULT_RUN_DIR "/vgs_online"
 #define PVS_LOOKUP_DIR DEFAULT_RUN_DIR "/pvs_lookup"
 
+#define DEVICES_IMPORT_PATH DEFAULT_RUN_DIR "/lvm-devices-import"
+
 #define DEFAULT_DEVICE_ID_SYSFS_DIR "/sys/"  /* trailing / to match dm_sysfs_dir() */
 
 #define DEFAULT_DEVICESFILE_BACKUP_LIMIT 50

lib/device/device_id.c

@@ -1726,9 +1726,10 @@ int device_ids_write(struct cmd_context *cmd)
 
 	if ((fc_bytes = snprintf(fc, sizeof(fc),
 			    "# LVM uses devices listed in this file.\n" \
-			    "# Created by LVM command %s pid %d at %s" \
+			    "# Created by LVM command %s%s pid %d at %s" \
 			    "# HASH=%u\n",
-			    cmd->name, getpid(), ctime(&t), hash)) < 0) {
+			    cmd->name, cmd->device_ids_auto_import ? " (auto)" : "",
+			    getpid(), ctime(&t), hash)) < 0) {
 		log_error("Failed to write buffer for devices file content.");
 		goto out;
 	}

scripts/lvm-devices-import.path

@@ -0,0 +1,12 @@
+[Unit]
+Description=lvm-devices-import to create system.devices
+
+# /run/lvm/lvm-devices-import created by vgchange -aay <rootvg>
+
+[Path]
+PathExists=/run/lvm/lvm-devices-import
+Unit=lvm-devices-import.service
+ConditionPathExists=!/etc/lvm/devices/system.devices
+
+[Install]
+WantedBy=multi-user.target

scripts/lvm-devices-import.service

@@ -0,0 +1,12 @@
+[Unit]
+Description=Create lvm system.devices
+
+[Service]
+Type=oneshot
+RemainAfterExit=no
+ExecStart=/usr/sbin/vgimportdevices --rootvg --auto
+ConditionPathExists=!/etc/lvm/devices/system.devices
+
+[Install]
+WantedBy=multi-user.target
+

tools/args.h

@@ -94,6 +94,14 @@ arg(atversion_ARG, '\0', "atversion", string_VAL, 0, 0,
     "which does not contain any newer settings for which LVM would\n"
     "issue a warning message when checking the configuration.\n")
 
+arg(auto_ARG, '\0', "auto", 0, 0, 0,
+    "This option is used when automatically importing devices for the root VG.\n"
+    "The auto import is intended to be done once, on first boot, to create an\n"
+    "initial system.devices file for the root VG.\n"
+    "When this option is used, the vgimportdevices --rootvg command does nothing\n"
+    "if system.devices exists, or the file auto-import-rootvg does not exist\n"
+    "(both in the /etc/lvm/devices/ directory.)\n")
+
 arg(autoactivation_ARG, '\0', "autoactivation", string_VAL, 0, 0,
     "Specify if autoactivation is being used from an event.\n"
     "This allows the command to apply settings that are specific\n"
@@ -754,6 +762,9 @@ arg(resync_ARG, '\0', "resync", 0, 0, 0,
     "which the LV is without a complete redundant copy of the data.\n"
     "See \\fBlvmraid\\fP(7) for more information.\n")
 
+arg(rootvg_ARG, '\0', "rootvg", 0, 0, 0,
+    "Import devices used for the root VG.\n")
+
 arg(rows_ARG, '\0', "rows", 0, 0, 0,
     "Output columns as rows.\n")
 

tools/command-lines.in

@@ -1911,6 +1911,11 @@ OO: --foreign, --reportformat ReportFmt
 ID: vgimportdevices_all
 DESC: Add devices from all accessible VGs to the devices file.
 
+vgimportdevices --rootvg
+OO: --auto, --reportformat ReportFmt
+ID: vgimportdevices_root
+DESC: Add devices from root VG to the devices file.
+
 ---
 
 vgmerge VG VG

tools/pvscan.c

@@ -495,7 +495,7 @@ static int _pvscan_aa_single(struct cmd_context *cmd, const char *vg_name,
 
 	log_debug("pvscan autoactivating VG %s.", vg_name);
 
-	if (!vgchange_activate(cmd, vg, CHANGE_AAY, 1)) {
+	if (!vgchange_activate(cmd, vg, CHANGE_AAY, 1, NULL)) {
 		log_error_pvscan(cmd, "%s: autoactivation failed.", vg->name);
 		pp->activate_errors++;
 	}
@@ -755,7 +755,7 @@ static int _pvscan_aa_quick(struct cmd_context *cmd, struct pvscan_aa_params *pp
 
 	log_debug("pvscan autoactivating VG %s.", vgname);
 
-	if (!vgchange_activate(cmd, vg, CHANGE_AAY, 1)) {
+	if (!vgchange_activate(cmd, vg, CHANGE_AAY, 1, NULL)) {
 		log_error_pvscan(cmd, "%s: autoactivation failed.", vg->name);
 		pp->activate_errors++;
 	}

tools/tools.h

@@ -164,7 +164,7 @@ int mirror_remove_missing(struct cmd_context *cmd,
 
 
 int vgchange_activate(struct cmd_context *cmd, struct volume_group *vg,
-		       activation_change_t activate, int vg_complete_to_activate);
+		       activation_change_t activate, int vg_complete_to_activate, char *root_dm_uuid);
 
 int vgchange_background_polling(struct cmd_context *cmd, struct volume_group *vg);
 

tools/vgchange.c

@@ -16,11 +16,14 @@
 #include "tools.h"
 #include "lib/device/device_id.h"
 #include "lib/label/hints.h"
+#include "device_mapper/misc/dm-ioctl.h"
+#include <mntent.h>
 
 struct vgchange_params {
 	int lock_start_count;
 	unsigned int lock_start_sanlock : 1;
 	unsigned int vg_complete_to_activate : 1;
+	char *root_dm_uuid; /* dm uuid of LV under root fs */
 };
 
 /*
@@ -197,7 +200,7 @@ int vgchange_background_polling(struct cmd_context *cmd, struct volume_group *vg
 }
 
 int vgchange_activate(struct cmd_context *cmd, struct volume_group *vg,
-		      activation_change_t activate, int vg_complete_to_activate)
+		      activation_change_t activate, int vg_complete_to_activate, char *root_dm_uuid)
 {
 	int lv_open, active, monitored = 0, r = 1;
 	const struct lv_list *lvl;
@@ -279,6 +282,43 @@ int vgchange_activate(struct cmd_context *cmd, struct volume_group *vg,
 		r = 0;
 	}
 
+	/*
+	 * Possibly trigger auto-generation of system.devices:
+	 * - if root_dm_uuid contains vg->id, and
+	 * - /etc/lvm/devices/auto-import-rootvg exists, and
+	 * - /etc/lvm/devices/system.devices does not exist, then
+	 * - create /run/lvm/lvm-devices-import to
+	 *   trigger lvm-devices-import.path and .service
+	 * - lvm-devices-import will run vgimportdevices --rootvg
+	 *   to create system.devices
+	 */
+	if (root_dm_uuid) {
+		char path[PATH_MAX];
+		struct stat info;
+		FILE *fp;
+
+		if (memcmp(root_dm_uuid + 4, &vg->id, ID_LEN))
+			goto out;
+
+		if (cmd->enable_devices_file || devices_file_exists(cmd))
+			goto out;
+
+		if (dm_snprintf(path, sizeof(path), "%s/devices/auto-import-rootvg", cmd->system_dir) < 0)
+			goto out;
+
+		if (stat(path, &info) < 0)
+			goto out;
+
+		log_debug("Found %s creating %s", path, DEVICES_IMPORT_PATH);
+
+		if (!(fp = fopen(DEVICES_IMPORT_PATH, "w"))) {
+			log_debug("failed to create %s", DEVICES_IMPORT_PATH);
+			goto out;
+		}
+		if (fclose(fp))
+			stack;
+	}
+out:
 	/* Print message only if there was not found a missing VG */
 	log_print_unless_silent("%d logical volume(s) in volume group \"%s\" now active",
 				lvs_in_vg_activated(vg), vg->name);
@@ -714,7 +754,7 @@ static int _vgchange_single(struct cmd_context *cmd, const char *vg_name,
 
 	if (arg_is_set(cmd, activate_ARG)) {
 		activate = (activation_change_t) arg_uint_value(cmd, activate_ARG, 0);
-		if (!vgchange_activate(cmd, vg, activate, vp->vg_complete_to_activate))
+		if (!vgchange_activate(cmd, vg, activate, vp->vg_complete_to_activate, vp->root_dm_uuid))
 			return_ECMD_FAILED;
 	} else if (arg_is_set(cmd, refresh_ARG)) {
 		/* refreshes the visible LVs (which starts polling) */
@@ -735,6 +775,115 @@ static int _vgchange_single(struct cmd_context *cmd, const char *vg_name,
 	return ret;
 }
 
+/*
+ * Automatic creation of system.devices for root VG on first boot
+ * is useful for OS images where the OS installer is not used to
+ * customize the OS for system.
+ *
+ * - OS image prep:
+ *   . rm /etc/lvm/devices/system.devices (if it exists)
+ *   . touch /etc/lvm/devices/auto-import-rootvg
+ *   . enable lvm-devices-import.path
+ *   . enable lvm-devices-import.service
+ *
+ * - lvchange -ay <rootvg>/<rootlv>
+ *   . run by initrd so root fs can be mounted
+ *   . does not use system.devices
+ *   . named <rootvg>/<rootlv> comes from kernel command line rd.lvm
+ *   . uses first device that appears containing the named root LV
+ *
+ * - vgchange -aay <rootvg>
+ *   . triggered by udev when all PVs from root VG are online
+ *   . activate LVs in root VG (in addition to the already active root LV)
+ *   . check for /etc/lvm/devices/auto-import-rootvg (found)
+ *   . check for /etc/lvm/devices/system.devices (not found)
+ *   . create /run/lvm/lvm-devices-import because
+ *     auto-import-rootvg was found and system.devices was not found
+ *
+ * - lvm-devices-import.path
+ *   . triggered by /run/lvm/lvm-devices-import
+ *   . start lvm-devices-import.service
+ *
+ * - lvm-devices-import.service
+ *   . check for /etc/lvm/devices/system.devices, do nothing if found
+ *   . run vgimportdevices --rootvg --auto
+ *
+ * - vgimportdevices --rootvg --auto
+ *   . check for /etc/lvm/devices/auto-import-rootvg (found)
+ *   . check for /etc/lvm/devices/system.devices (not found)
+ *   . creates /etc/lvm/devices/system.devices for PVs in root VG
+ *   . removes /etc/lvm/devices/auto-import-rootvg
+ *   . removes /run/lvm/lvm-devices-import
+ *
+ * On future startup, /etc/lvm/devices/system.devices will exist,
+ * and /etc/lvm/devices/auto-import-rootvg will not exist, so
+ * vgchange -aay <rootvg> will not create /run/lvm/lvm-devices-import,
+ * and lvm-devices-import.path and lvm-device-import.service will not run.
+ *
+ * lvm-devices-import.path:
+ * [Path]
+ * PathExists=/run/lvm/lvm-devices-import
+ * Unit=lvm-devices-import.service
+ * ConditionPathExists=!/etc/lvm/devices/system.devices
+ *
+ * lvm-devices-import.service:
+ * [Service]
+ * Type=oneshot
+ * RemainAfterExit=no
+ * ExecStart=/usr/sbin/vgimportdevices --rootvg --auto
+ * ConditionPathExists=!/etc/lvm/devices/system.devices
+ */
+
+static void _get_rootvg_dev(struct cmd_context *cmd, char **dm_uuid_out)
+{
+	char path[PATH_MAX];
+	char dm_uuid[DM_UUID_LEN];
+	struct stat info;
+	FILE *fme = NULL;
+	struct mntent *me;
+	int found = 0;
+
+	if (cmd->enable_devices_file || devices_file_exists(cmd))
+		return;
+
+	if (dm_snprintf(path, sizeof(path), "%s/devices/auto-import-rootvg", cmd->system_dir) < 0)
+		return;
+
+	if (stat(path, &info) < 0)
+		return;
+
+	if (!(fme = setmntent("/etc/mtab", "r")))
+		return;
+
+	while ((me = getmntent(fme))) {
+		if ((me->mnt_dir[0] == '/') && (me->mnt_dir[1] == '\0')) {
+			found = 1;
+			break;
+		}
+	}
+	endmntent(fme);
+
+	if (!found)
+		return;
+
+	if (stat(me->mnt_dir, &info) < 0)
+		return;
+
+	if (!get_dm_uuid_from_sysfs(dm_uuid, sizeof(dm_uuid), (int)MAJOR(info.st_dev), (int)MINOR(info.st_dev)))
+		return;
+
+	log_debug("Found root dm_uuid %s", dm_uuid);
+
+	/* UUID_PREFIX = "LVM-" */
+	if (strncmp(dm_uuid, UUID_PREFIX, 4))
+		return;
+
+	if (strlen(dm_uuid) < 4 + ID_LEN)
+		return;
+
+	*dm_uuid_out = dm_pool_strdup(cmd->mem, dm_uuid);
+}
+
 static int _vgchange_autoactivation_setup(struct cmd_context *cmd,
 					  struct vgchange_params *vp,
 					  int *skip_command,
@@ -778,6 +927,8 @@ static int _vgchange_autoactivation_setup(struct cmd_context *cmd,
 
 	get_single_vgname_cmd_arg(cmd, NULL, &vgname);
 
+	_get_rootvg_dev(cmd, &vp->root_dm_uuid);
+
 	/*
 	 * Lock the VG before scanning the PVs so _vg_read can avoid the normal
 	 * lock_vol+rescan (READ_WITHOUT_LOCK avoids the normal lock_vol and

tools/vgimportdevices.c

@@ -15,11 +15,16 @@
 #include "tools.h"
 #include "lib/cache/lvmcache.h"
 #include "lib/device/device_id.h"
+#include "device_mapper/misc/dm-ioctl.h"
 /* coverity[unnecessary_header] needed for MuslC */
 #include <sys/file.h>
+#include <mntent.h>
 
 struct vgimportdevices_params {
 	uint32_t added_devices;
+	int root_vg_found;
+	char *root_dm_uuid;
+	char *root_vg_name;
 };
 
 static int _vgimportdevices_single(struct cmd_context *cmd,
@@ -35,6 +40,13 @@ static int _vgimportdevices_single(struct cmd_context *cmd,
 	int updated_pvs = 0;
 	const char *idtypestr = NULL; /* deviceidtype_ARG ? */
 
+	if (vp->root_dm_uuid) {
+		if (memcmp(vp->root_dm_uuid + 4, &vg->id, ID_LEN))
+			return ECMD_PROCESSED;
+		vp->root_vg_found = 1;
+		vp->root_vg_name = dm_pool_strdup(cmd->mem, vg_name);
+	}
+
 	dm_list_iterate_items(pvl, &vg->pvs) {
 		if (is_missing_pv(pvl->pv) || !pvl->pv->dev) {
 			memcpy(pvid, &pvl->pv->id.uuid, ID_LEN);
@@ -86,6 +98,87 @@ static int _vgimportdevices_single(struct cmd_context *cmd,
 	return ECMD_PROCESSED;
 }
 
+static int _get_rootvg_dev(struct cmd_context *cmd, char **dm_uuid_out, int *skip)
+{
+	char path[PATH_MAX];
+	char dm_uuid[DM_UUID_LEN];
+	struct stat info; 
+	FILE *fme = NULL;
+	struct mntent *me;
+	int found = 0;
+
+	/*
+	 * When --auto is set, the command does nothing
+	 * if /etc/lvm/devices/system.devices exists, or
+	 * if /etc/lvm/devices/auto-import-rootvg does not exist.
+	 */
+	if (arg_is_set(cmd, auto_ARG)) {
+		if (devices_file_exists(cmd)) {
+			*skip = 1;
+			return 1;
+		}
+
+		if (dm_snprintf(path, sizeof(path), "%s/devices/auto-import-rootvg", cmd->system_dir) < 0)
+			return_0;
+
+		if (stat(path, &info) < 0) {
+			*skip = 1;
+			return 1;
+		}
+
+		/*
+		 * This flag is just used in device_ids_write to enable
+		 * an extra comment in system.devices indicating that
+		 * the file was auto generated for the root vg.
+		 */
+		cmd->device_ids_auto_import = 1;
+	}
+
+	if (!(fme = setmntent("/etc/mtab", "r")))
+		return_0;
+
+	while ((me = getmntent(fme))) {
+		if ((me->mnt_dir[0] == '/') && (me->mnt_dir[1] == '\0')) {
+			found = 1;
+			break;
+		}
+	}
+	endmntent(fme);
+
+	if (!found)
+		return_0;
+
+	if (stat(me->mnt_dir, &info) < 0)
+		return_0;
+
+	if (!get_dm_uuid_from_sysfs(dm_uuid, sizeof(dm_uuid), (int)MAJOR(info.st_dev), (int)MINOR(info.st_dev)))
+		return_0;
+
+	/* UUID_PREFIX = "LVM-" */
+	if (strncmp(dm_uuid, UUID_PREFIX, 4))
+		return_0;
+
+	if (strlen(dm_uuid) < 4 + ID_LEN)
+		return_0;
+
+	*dm_uuid_out = dm_pool_strdup(cmd->mem, dm_uuid);
+	return 1;
+}
+
+static void _clear_rootvg_auto(struct cmd_context *cmd)
+{
+	char path[PATH_MAX];
+
+	if (dm_snprintf(path, sizeof(path), "%s/devices/auto-import-rootvg", cmd->system_dir) < 0)
+		return;
+
+	if (unlink(path) < 0)
+		log_debug("Failed to unlink %s", path);
+
+	if (unlink(DEVICES_IMPORT_PATH) < 0)
+		log_debug("Failed to unlink %s", DEVICES_IMPORT_PATH);
+}
+
 /*
  * This command always scans all devices on the system,
  * any pre-existing devices_file does not limit the scope.
@@ -130,6 +223,19 @@ int vgimportdevices(struct cmd_context *cmd, int argc, char **argv)
 	/* So that we can warn about this. */
 	cmd->handles_missing_pvs = 1;
 
+	/* Import devices for the root VG. */
+	if (arg_is_set(cmd, rootvg_ARG)) {
+		int skip = 0;
+		if (!_get_rootvg_dev(cmd, &vp.root_dm_uuid, &skip)) {
+			log_error("Failed to find root VG.");
+			return ECMD_FAILED;
+		}
+		if (skip) {
+			log_print("Root VG auto import is not enabled.");
+			return ECMD_PROCESSED;
+		}
+	}
+
 	if (!lock_global(cmd, "ex"))
 		return ECMD_FAILED;
 
@@ -230,7 +336,13 @@ int vgimportdevices(struct cmd_context *cmd, int argc, char **argv)
 		goto out;
 	}
 
-	log_print("Added %u devices to devices file.", vp.added_devices);
+	if (vp.root_vg_found)
+		log_print("Added %u devices to devices file for root VG %s.", vp.added_devices, vp.root_vg_name);
+	else
+		log_print("Added %u devices to devices file.", vp.added_devices);
+
+	if (vp.root_vg_found && arg_is_set(cmd, auto_ARG))
+		_clear_rootvg_auto(cmd);
 out:
 	if ((ret == ECMD_FAILED) && created_file)
 		if (unlink(cmd->devices_file_path) < 0)