[Libguestfs] [PATCH v2] rescue: add --autosysroot option RHBZ#1183493
Maros Zatko
mzatko at redhat.com
Thu Jun 16 14:13:24 UTC 2016
On 06/09/2016 03:18 PM, Pino Toscano wrote:
> In data mercoledì 1 giugno 2016 02:04:33, Maros Zatko ha scritto:
>> --autosysroot option uses suggestions to user on how to mount filesystems
>> and change root suggested by --suggest option in virt-rescue.
> IMHO it should be called -i, like in the other tools, as what
> --autosysroot does is basically the same.
We can call it -i, I don't mind, I've implemented this as was in RFE.
>
>> 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.
> Passing arbitrary commands might not be the best idea ever -- other than
> potentially running into issues such as quoting and escaping, the length
> of the boot command line of the Linux kernel is limited [1], and we are
> already using more than 200 characters.
What about escaping, have you found a counter-example?
I don't see much problem with this limit either, have we run into an
issue? It seems that
max allowed size is about 4KiB (between 256 and 4KiB) and we're running a VM
so I don't ever expect this to be a problem.
>
> An alternative approach with the cmdline could be passing like
> guestfs_mount=/dev:/mntpoint:opts, which is slightly more complex to
> parse, although provide a more strict interface and requires no eval.
>
> [1] https://www.kernel.org/doc/Documentation/kernel-parameters.txt
Hm, this introduces another type of splitter (:) and we would have to
think about escaping it too
(but this time it's not done by bash itself) - what if : is included in
filename?
>> On successfull run user is presented directly with bash in chroot
>> environment.
> I'd not do that -- one of the way virt-rescue is useful is work on
> the guest using the tools available in the appliance, so having an
> an option to mount all the filesystems while still be in the appliance
> would be the optimal thing to do IMHO.
I don't get this, --autosysroot is meant to be "optimization" so one
doesn't have to copy-paste
any commands and this feature is what was requested in RFE, and user
doesn't have to use this automagic.
>
> In this situation, printing a "you can chroot in the guest by
> running ..." message just before running bash would help too.
>
>> Resolves RFE: RHBZ#1183493
>> ---
>> appliance/init | 5 ++
>> rescue/rescue.c | 169 +++++++++++++++++++++++++++++++++++++++++++++-----------
>> 2 files changed, 143 insertions(+), 31 deletions(-)
>>
>> diff --git a/appliance/init b/appliance/init
>> index 3fdf4d0..0a76398 100755
>> --- a/appliance/init
>> +++ b/appliance/init
>> @@ -192,6 +192,11 @@ 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 135c9e6..77b6544 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 +50,9 @@ int echo_keys = 0;
>> const char *libvirt_uri = NULL;
>> int inspector = 0;
>>
>> +static void use_suggestions (char **cmds);
>> +static void parse_opts(int argc, char * argv[]);
>> +
>> static void __attribute__((noreturn))
>> usage (int status)
>> {
>> @@ -65,6 +68,8 @@ usage (int status)
>> "Options:\n"
>> " -a|--add image Add image\n"
>> " --append kernelopts Append kernel options\n"
>> + " --autosysroot Automatically use suggested mount commands\n"
>> + " and chroot to guest. Needs --suggest to work\n"
> Hm I see --suggest and --autosysroot as separate modes:
>
> * --suggests inspects the guest, prints all the mount commands for the
> guest, and exits
>
> * --autosysroot starts the appliance, and mounts all the filesystems,
> letting the user continue with the rest of the wanted work
>
>> " -c|--connect uri Specify libvirt URI for -d option\n"
>> " -d|--domain guest Add disks from libvirt guest\n"
>> " --format[=raw|..] Force disk format for -a option\n"
>> @@ -87,21 +92,30 @@ 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;
> Any reason these are turned into global variables?
These are filled in option parser and used elsewhere, it didn't
seem to make sense to make it more complicated for this simple program.
These were used as if they were global variables before, difference was
that they were used
in one large function (main) and their initialization was not factored
out to function so
their 'global' sense/semantics didn't really change.
>
>> +static void
>> +parse_opts(int argc, char * argv[])
>> +{
> Not a problematic change, but I'd do it in a separate patch.
>
>> 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 +134,10 @@ 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 +152,9 @@ 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 +263,71 @@ 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) {
> strcmp -> STREQ
yup
>
>> + 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;
>> + format_consumed = true;
>> + c = 0;
>> + option_index = 0;
>> + network = 0;
>> + if (append) free(append);
> free() accepts (by standard) also NULL as argument, so this check is
> redundant.
>
>> + 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;
> I'm puzzled -- why do you need to parse the arguments again? You have
> all the options already, so just create a new handle, and set the
> options for it.
Because we need to reinitialize stuff - library and so - and options
should be constructed a bit different when
we want to just inspect and when we need r/w access.
>
> Also, 'args' is not free'd.
>
>> + }
>> + } else {
>> + if (autosysroot) {
>> + fprintf (stderr, _("%s: warning: --autosysroot used without --suggest.\n"),
>> + guestfs_int_program_name);
>> + }
>> }
>>
>> /* These are really constants, but they have to be variables for the
>> @@ -313,6 +378,11 @@ 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)
>> @@ -367,14 +437,34 @@ 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);
>> + }
> I'd loop over the commands, calculate the length of the resulting
> string, allocate once the needed string, and then loop again filling
> it.
>
>> +}
>> +
>> /* 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 = malloc (sizeof (char*));
>> + cmds[0] = NULL;
>> +
>>
>> /* For inspection, force add_drives to add the drives read-only. */
>> read_only = 1;
>> @@ -401,7 +491,7 @@ do_suggestion (struct drv *drvs)
>>
>> if (roots[0] == NULL) {
>> suggest_filesystems ();
>> - return;
>> + return NULL;
> 'cmds' is leaked here.
>
>> }
>>
>> printf (_("This disk contains one or more operating systems. You can use these mount\n"
>> @@ -436,10 +526,16 @@ 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);
> The number of elements (excluding the terminal NULL) can be stored in
> a variable and incremented, no need to recalculate it every iteration.
>
>> + cmds = realloc (cmds, sizeof (char *) * (cnt + 2));
>> +
>> + cmds[cnt] = xasprintf ("mount %s /sysroot%s", mps[j+1], mps[j]);
>> + cmds[cnt+1] = NULL;
>> + }
> Since the number of commands is known, loop over once to calculate the
> number of elements for 'cmds'.
>
> Thanks,
Thank you for reviewing! I'll be back with corrections.
- m
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