Libguestfs - Jul 2010 - [PATCH] New APIs: findfs-label and findfs-uuid

These APIs are needed for ease of inspection of /etc/fstab from C.

(Actually the way we are doing it currently in Perl is incredibly
convoluted .. we should have just used findfs).

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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>From c10cdec2418dbcf2fed9605365402d4cfc75eff3 Mon Sep 17 00:00:00 2001
From: Richard Jones <rjones at redhat.com>
Date: Wed, 28 Jul 2010 23:11:38 +0100
Subject: [PATCH] New APIs: findfs-label and findfs-uuid

These two calls wrap up the /sbin/findfs command, allowing you
to find a filesystem by only knowing its label or UUID.

This is especially useful when resolving LABEL=... or UUID=...
entries in /etc/fstab.

Sample guestfish session:
><fs> vfs-uuid /dev/vda1
277dd61c-bf34-4253-a8dc-df500a05e7df
><fs> findfs-uuid 277dd61c-bf34-4253-a8dc-df500a05e7df
/dev/vda1
><fs> vfs-label /dev/vda1
/boot
><fs> findfs-label /boot
/dev/vda1
><fs> vfs-uuid /dev/VolGroup00/LogVol00
40ce7c36-82ce-4a12-a99d-48f5e054162c
><fs> findfs-uuid 40ce7c36-82ce-4a12-a99d-48f5e054162c
/dev/mapper/VolGroup00-LogVol00
><fs> findfs-uuid 12345678
libguestfs: error: findfs_uuid: findfs: unable to resolve
'UUID=12345678'
---
 daemon/Makefile.am |    1 +
 daemon/findfs.c    |   72 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 po/POTFILES.in     |    1 +
 src/MAX_PROC_NR    |    2 +-
 src/generator.ml   |   28 ++++++++++++++++++-
 5 files changed, 101 insertions(+), 3 deletions(-)
 create mode 100644 daemon/findfs.c

diff --git a/daemon/Makefile.am b/daemon/Makefile.am
index 27fca2a..0c8be08 100644
--- a/daemon/Makefile.am
+++ b/daemon/Makefile.am
@@ -84,6 +84,7 @@ guestfsd_SOURCES = \
 	ext2.c \
 	fallocate.c \
 	file.c \
+	findfs.c \
 	fill.c \
 	find.c \
 	fsck.c \
diff --git a/daemon/findfs.c b/daemon/findfs.c
new file mode 100644
index 0000000..cdce4a0
--- /dev/null
+++ b/daemon/findfs.c
@@ -0,0 +1,72 @@
+/* libguestfs - the guestfsd daemon
+ * Copyright (C) 2009 Red Hat Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <config.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include "daemon.h"
+#include "actions.h"
+
+static char *
+findfs (const char *tag, const char *label_or_uuid)
+{
+  /* Kill the cache file, forcing blkid to reread values from the
+   * original filesystems.  In blkid there is a '-p' option which is
+   * supposed to do this, but (a) it doesn't work and (b) that option
+   * is not supported in RHEL 5.
+   */
+  unlink ("/etc/blkid/blkid.tab");
+
+  size_t len = strlen (tag) + strlen (label_or_uuid) + 2;
+  char arg[len];
+  snprintf (arg, len, "%s=%s", tag, label_or_uuid);
+
+  char *out, *err;
+  int r = command (&out, &err, "findfs", arg, NULL);
+  if (r == -1) {
+    reply_with_error ("%s", err);
+    free (out);
+    free (err);
+    return NULL;
+  }
+
+  free (err);
+
+  /* Trim trailing \n if present. */
+  len = strlen (out);
+  if (len > 0 && out[len-1] == '\n')
+    out[len-1] = '\0';
+
+  return out;                   /* caller frees */
+}
+
+char *
+do_findfs_uuid (const char *uuid)
+{
+  return findfs ("UUID", uuid);
+}
+
+char *
+do_findfs_label (const char *label)
+{
+  return findfs ("LABEL", label);
+}
diff --git a/po/POTFILES.in b/po/POTFILES.in
index bf066ea..8ce5c97 100644
--- a/po/POTFILES.in
+++ b/po/POTFILES.in
@@ -21,6 +21,7 @@ daemon/fallocate.c
 daemon/file.c
 daemon/fill.c
 daemon/find.c
+daemon/findfs.c
 daemon/fsck.c
 daemon/glob.c
 daemon/grep.c
diff --git a/src/MAX_PROC_NR b/src/MAX_PROC_NR
index 175b6c5..2b930fc 100644
--- a/src/MAX_PROC_NR
+++ b/src/MAX_PROC_NR
@@ -1 +1 @@
-263
+265
diff --git a/src/generator.ml b/src/generator.ml
index 04a675a..66453e0 100755
--- a/src/generator.ml
+++ b/src/generator.ml
@@ -4952,7 +4952,9 @@ a file in the host and attach it as a device.");
 This returns the filesystem label of the filesystem on
 C<device>.
 
-If the filesystem is unlabeled, this returns the empty string.");
+If the filesystem is unlabeled, this returns the empty string.
+
+To find a filesystem from the label, use C<guestfs_findfs_label>.");
 
   ("vfs_uuid", (RString "uuid", [Device
"device"]), 254, [],
    (let uuid = uuidgen () in
@@ -4964,7 +4966,9 @@ If the filesystem is unlabeled, this returns the empty
string.");
 This returns the filesystem UUID of the filesystem on
 C<device>.
 
-If the filesystem does not have a UUID, this returns the empty string.");
+If the filesystem does not have a UUID, this returns the empty string.
+
+To find a filesystem from the UUID, use C<guestfs_findfs_uuid>.");
 
   ("lvm_set_filter", (RErr, [DeviceList "devices"]), 255,
[Optional "lvm2"],
    (* Can't be tested with the current framework because
@@ -5081,6 +5085,26 @@ This command deletes the key in key slot C<keyslot>
from the
 encrypted LUKS device C<device>.  C<key> must be one of the
 I<other> keys.");
 
+  ("findfs_uuid", (RString "device", [String
"uuid"]), 264, [],
+   [],
+   "find a filesystem by UUID",
+   "\
+This command searches the filesystems and returns the one
+which has the given UUID.  An error is returned if no such
+filesystem can be found.
+
+To find the UUID of a filesystem, use C<guestfs_vfs_uuid>.");
+
+  ("findfs_label", (RString "device", [String
"label"]), 265, [],
+   [],
+   "find a filesystem by label",
+   "\
+This command searches the filesystems and returns the one
+which has the given label.  An error is returned if no such
+filesystem can be found.
+
+To find the label of a filesystem, use C<guestfs_vfs_label>.");
+
 ]
 
 let all_functions = non_daemon_functions @ daemon_functions
-- 
1.7.1