Libguestfs - May 2016 - [PATCH] rescue: add --autosysroot option RHBZ#1183493

--autosysroot option uses suggestions to user on how to mount filesystems
and change root suggested by --suggest option in virt-rescue.

Commands are passed on kernel command line in format
guestfs_command=command;. Command ends with a semicolon and there can be
multiple commands specified. These are executed just before bash starts.
On successfull run user is presented directly with bash in chroot
environment.

RFE: RHBZ#1183493
Depends on commit: utils: make guestfs_int_count_strings return 0 on NULL input

Maros Zatko (1):
  rescue: add --autosysroot option RHBZ#1183493

 appliance/init  |   6 +++
 rescue/rescue.c | 160 ++++++++++++++++++++++++++++++++++++++++++++------------
 2 files changed, 134 insertions(+), 32 deletions(-)

-- 
2.5.5

--autosysroot option uses suggestions to user on how to mount filesystems
and change root suggested by --suggest option in virt-rescue.

Commands are passed on kernel command line in format
guestfs_command=command;. Command ends with a semicolon and there can be
multiple commands specified. These are executed just before bash starts.
On successfull run user is presented directly with bash in chroot
environment.

RFE: RHBZ#1183493
Depends on commit: utils: make guestfs_int_count_strings return 0 on NULL input
---
 appliance/init  |   6 +++
 rescue/rescue.c | 160 ++++++++++++++++++++++++++++++++++++++++++++------------
 2 files changed, 134 insertions(+), 32 deletions(-)

diff --git a/appliance/init b/appliance/init
index 413a95f..82dac9f 100755
--- a/appliance/init
+++ b/appliance/init
@@ -182,6 +182,7 @@ else
 
   :> $HOME/.bashrc
   grep -Eo 'TERM=[^[:space:]]+' /proc/cmdline >> $HOME/.bashrc
+
   echo "PS1='><rescue> '" >> $HOME/.bashrc
   echo "export TERM PS1" >> $HOME/.bashrc
 
@@ -194,6 +195,11 @@ else
   echo "You have to mount the guest's partitions under /sysroot"
   echo "before you can examine them."
   echo
+  echo 'Executing commands from kernel cmdline'
+
+  grep -Eo 'guestfs_command=([^;]+);[[:space:]]*' /proc/cmdline | sed
-n 's/guestfs_command=\(.*;\)/\1/p'
+  eval $(grep -Eo 'guestfs_command=([^;]+);[[:space:]]*' /proc/cmdline
| sed -n 's/guestfs_command=\(.*;\)/\1/p')
+
   bash -i
   echo
   echo "virt-rescue: Syncing the disk now before exiting ..."
diff --git a/rescue/rescue.c b/rescue/rescue.c
index c46c775..9311d9e 100644
--- a/rescue/rescue.c
+++ b/rescue/rescue.c
@@ -37,7 +37,7 @@
 #include "options.h"
 
 static void add_scratch_disks (int n, struct drv **drvs);
-static void do_suggestion (struct drv *drvs);
+static char ** do_suggestion (struct drv *drvs);
 
 /* Currently open libguestfs handle. */
 guestfs_h *g;
@@ -50,6 +50,8 @@ int echo_keys = 0;
 const char *libvirt_uri = NULL;
 int inspector = 0;
 
+static void use_suggestions (char * *cmds);
+
 static void __attribute__((noreturn))
 usage (int status)
 {
@@ -87,21 +89,27 @@ usage (int status)
   exit (status);
 }
 
-int
-main (int argc, char *argv[])
-{
-  setlocale (LC_ALL, "");
-  bindtextdomain (PACKAGE, LOCALEBASEDIR);
-  textdomain (PACKAGE);
-
-  parse_config ();
-
+  struct drv *drvs = NULL;
+  struct drv *drv;
+  char * *cmds = NULL;
+  const char *format = NULL;
+  bool format_consumed = true;
+  int c;
+  int option_index;
+  int network = 0;
+  char *append = NULL;
+  int memsize = 0;
+  int smp = 0;
+  int suggest = 0;
+  int autosysroot = 0;
+void parse_opts(int argc, char * argv[]) {
   enum { HELP_OPTION = CHAR_MAX + 1 };
 
   static const char *options = "a:c:d:m:rvVx";
   static const struct option long_options[] = {
     { "add", 1, 0, 'a' },
     { "append", 1, 0, 0 },
+    { "autosysroot", 0, 0, 0 },
     { "connect", 1, 0, 'c' },
     { "domain", 1, 0, 'd' },
     { "format", 2, 0, 0 },
@@ -120,22 +128,10 @@ main (int argc, char *argv[])
     { "version", 0, 0, 'V' },
     { 0, 0, 0, 0 }
   };
-  struct drv *drvs = NULL;
-  struct drv *drv;
-  const char *format = NULL;
-  bool format_consumed = true;
-  int c;
-  int option_index;
-  int network = 0;
-  const char *append = NULL;
-  int memsize = 0;
-  int smp = 0;
-  int suggest = 0;
 
-  g = guestfs_create ();
-  if (g == NULL)
-    error (EXIT_FAILURE, errno, "guestfs_create");
 
+  option_index = 0;
+  optind = 0;
   for (;;) {
     c = getopt_long (argc, argv, options, long_options, &option_index);
     if (c == -1) break;
@@ -150,7 +146,9 @@ main (int argc, char *argv[])
         if (guestfs_set_selinux (g, 1) == -1)
           exit (EXIT_FAILURE);
       } else if (STREQ (long_options[option_index].name, "append")) {
-        append = optarg;
+        append = strdup (optarg);
+      } else if (STREQ (long_options[option_index].name,
"autosysroot")) {
+        autosysroot = 1;
       } else if (STREQ (long_options[option_index].name, "network"))
{
         network = 1;
       } else if (STREQ (long_options[option_index].name, "format")) {
@@ -259,10 +257,67 @@ main (int argc, char *argv[])
     }
   }
 
+}
+
+int
+main (int argc, char *argv[])
+{
+  setlocale (LC_ALL, "");
+  bindtextdomain (PACKAGE, LOCALEBASEDIR);
+  textdomain (PACKAGE);
+
+  parse_config ();
+  g = guestfs_create ();
+  if (g == NULL)
+    error (EXIT_FAILURE, errno, "guestfs_create");
+
+  parse_opts (argc, argv);
+
   /* --suggest flag */
   if (suggest) {
-    do_suggestion (drvs);
-    exit (EXIT_SUCCESS);
+    cmds = do_suggestion (drvs);
+    if (!autosysroot) {
+      exit (EXIT_SUCCESS);
+    } else {
+      /* Shut down libguestfs so we can start a new one */
+      guestfs_shutdown (g);
+      guestfs_close (g);
+
+      /* remove --suggest flag */
+      size_t newcount = argc;
+      for (int i = 0; i < argc; i++) {
+        if (strcmp (argv[i], "--suggest") == 0) {
+          newcount--;
+        }
+      }
+
+      char ** args = malloc (sizeof (char*) * (newcount));
+      for (int i = 0, j = 0; i < argc; i++) {
+        if (strcmp (argv[i], "--suggest") != 0) {
+          args[j] = strdup (argv[i]);
+          j++;
+        }
+      }
+
+      /* clear options */
+      drvs = NULL;
+      if (format) free(format);
+      format_consumed = true;
+      c = 0;
+      option_index = 0;
+      network = 0;
+      if (append) free(append);
+      memsize = 0;
+      smp = 0;
+      suggest = 0;
+      autosysroot = 0;
+
+      /* Create new guestfs handle, this time for rescue instead of OS
detection */
+      g = guestfs_create ();
+      /* Parse options with --suggest flag removed */
+      parse_opts (newcount, args);
+      argc = newcount;
+    }
   }
 
   /* These are really constants, but they have to be variables for the
@@ -305,6 +360,11 @@ main (int argc, char *argv[])
     }
   }
 
+  /* Now it's time to set suggestions. */
+  if (autosysroot) {
+    use_suggestions (cmds);
+  }
+
   /* Set other features. */
   if (memsize > 0)
     if (guestfs_set_memsize (g, memsize) == -1)
@@ -359,14 +419,33 @@ compare_keys_len (const void *p1, const void *p2)
   return strlen (key1) - strlen (key2);
 }
 
+/* Use autodetected suggested filesystems */
+static void
+use_suggestions (char * *cmds)
+{
+  size_t i;
+  if (cmds == NULL) return;
+  read_only = 0;
+
+  /* Craft kernel command line from suggested commands */
+  for (i = 0; cmds[i] != NULL; i++) {
+    char *old_append = append;
+    append = xasprintf ("%s guestfs_command=%s;", append == NULL?
"" : append, cmds[i]);
+    if (old_append != NULL)
+      free (old_append);
+  }
+}
+
 /* virt-rescue --suggest flag does a kind of inspection on the
  * drives and suggests mount commands that you should use.
  */
-static void
+static char **
 do_suggestion (struct drv *drvs)
 {
   CLEANUP_FREE_STRING_LIST char **roots = NULL;
   size_t i;
+  char * *cmds = NULL;
+
 
   /* For inspection, force add_drives to add the drives read-only. */
   read_only = 1;
@@ -393,7 +472,7 @@ do_suggestion (struct drv *drvs)
 
   if (roots[0] == NULL) {
     suggest_filesystems ();
-    return;
+    return NULL;
   }
 
   printf (_("This disk contains one or more operating systems.  You can
use these mount\n"
@@ -428,10 +507,16 @@ do_suggestion (struct drv *drvs)
     qsort (mps, guestfs_int_count_strings (mps) / 2, 2 * sizeof (char *),
            compare_keys_len);
 
-    for (j = 0; mps[j] != NULL; j += 2)
-      printf ("mount %s /sysroot%s\n", mps[j+1], mps[j]);
+    /* First we save commands to mount system root. */
+    for (j = 0; mps[j] != NULL; j += 2) {
+      int cnt = guestfs_int_count_strings (cmds);
+      cmds = realloc (cmds, sizeof (char *) * (cnt + 2));
 
-    /* If it's Linux, print the bind-mounts and a chroot command. */
+      cmds[cnt] = xasprintf ("mount %s /sysroot%s", mps[j+1],
mps[j]);
+      cmds[cnt+1] = NULL;
+    }
+
+    /* If it's Linux, print the bind-mounts and a chroot command and save
them. */
     if (type && STREQ (type, "linux")) {
       printf ("mount --rbind /dev /sysroot/dev\n");
       printf ("mount --rbind /proc /sysroot/proc\n");
@@ -439,10 +524,21 @@ do_suggestion (struct drv *drvs)
       printf ("\n");
       printf ("cd /sysroot\n");
       printf ("chroot /sysroot\n");
+
+      int cnt = guestfs_int_count_strings (cmds);
+      cmds = realloc (cmds, sizeof (char *) * (cnt + 6));
+
+      cmds[cnt+0] = xasprintf ("mount --rbind /dev /sysroot/dev");
+      cmds[cnt+1] = xasprintf ("mount --rbind /proc /sysroot/proc");
+      cmds[cnt+2] = xasprintf ("mount --rbind /sys /sysroot/sys");
+      cmds[cnt+3] = xasprintf ("cd /sysroot");
+      cmds[cnt+4] = xasprintf ("chroot /sysroot");
+      cmds[cnt+5] = NULL;
     }
 
     printf ("\n");
   }
+  return cmds;
 }
 
 /* Inspection failed, so it doesn't contain any OS that we recognise.
-- 
2.5.5