Pino Toscano
2016-Jun-09 13:18 UTC
Re: [Libguestfs] [PATCH v2] rescue: add --autosysroot option RHBZ#1183493
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.> 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. 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> 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. 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?> +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> + 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. 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, -- Pino Toscano
Maros Zatko
2016-Jun-16 14:13 UTC
Re: [Libguestfs] [PATCH v2] rescue: add --autosysroot option RHBZ#1183493
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.txtHm, 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 -> STREQyup> >> + 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
Pino Toscano
2016-Jun-17 13:12 UTC
Re: [Libguestfs] [PATCH v2] rescue: add --autosysroot option RHBZ#1183493
On Thursday 16 June 2016 16:13:24 Maros Zatko wrote:> 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.That's a suggestion of course :) It's our task to make sure new features are properly integrate with the rest of the implementation.> >> 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?You are not quoting nor escaping the commands added, for 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.Exceeding the limits means our arguments will be cut off, so things will not work as expected because less arguments are read/used.> > 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?We already use this syntax in -m/--mount parameters of various tools.> >> 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.Sure, however mounting and chroot means you have no benefit if you want to only mount everything but still work outside the guest. Since chroot is just a single command which can be suggested before running bash, IMHO it'd be much better to automate what requires more manual work (inspection + mount).> >> -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.My point was about whether the actual change in this patch was really needed -- having patches doing specific changes instead of mixing different changes together helps in reviewing and debugging.> >> + 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.The current option parsing already reads everything in variables (except the selinux option, but that be easily changed), so all you need to do is creating a new handle and setting up everything. Other than the read_only behaviour (which does not depend on the options, but on a global variable), what are differences do you see? Thanks, -- Pino Toscano
Apparently Analagous Threads
- [PATCH v2] rescue: add --autosysroot option RHBZ#1183493
- Re: [PATCH v2] rescue: add --autosysroot option RHBZ#1183493
- [PATCH] rescue: add --autosysroot option RHBZ#1183493
- [PATCH v2] rescue: add --autosysroot option RHBZ#1183493
- [PATCH v2 1/2] New tool: virt-tail.