[parted-devel] [PATCH] Add autofix: Automatically "Fix" in script mode

[Cristian Klein]

Use-case: VMs are booted from images that are smaller than their virtual
disk. This means that -- almost by definition -- the secondary GPT
header will be "misplaced", i.e., not at the end of the virtual disk.

Without this patch, parted cannot be used for custom/exotic partitioning
when the VM boots (e.g., in cloud-init's `bootcmd`). Specifically, it
will fail as follows:

```
$ sudo parted --script /dev/vda "mkpart 2 10GB -1"
Warning: Not all of the space available to /dev/vda appears to be used,
you can fix the GPT to use all of the space (an extra 500 blocks) or continue with the current setting?
Error: Unable to satisfy all constraints on the partition.
```

This happens because, in script mode, exceptions are usually not
resolved.

This patch adds `--autofix`. This allows exceptions to be automatically
resolved with Fix. As a result, the following command will work:

```
$ sudo parted autofix --script /dev/vda "mkpart 2 10GB -1"
```
---
 parted/parted.c | 4 ++++
 parted/ui.c     | 6 ++++++
 parted/ui.h     | 1 +
 3 files changed, 11 insertions(+)

diff --git a/parted/parted.c b/parted/parted.c
index dbd38d0..36d1201 100644
--- a/parted/parted.c
+++ b/parted/parted.c
@@ -115,6 +115,7 @@ static struct option const options[] = {
         {"list",        0, NULL, 'l'},
         {"machine",     0, NULL, 'm'},
         {"script",      0, NULL, 's'},
+        {"autofix",     0, NULL, 'f'},
         {"version",     0, NULL, 'v'},
         {"align",       required_argument, NULL, 'a'},
         {"-pretend-input-tty", 0, NULL, PRETEND_INPUT_TTY},
@@ -126,12 +127,14 @@ static const char *const options_help [][2] = {
         {"list",        N_("lists partition layout on all block devices")},
         {"machine",     N_("displays machine parseable output")},
         {"script",      N_("never prompts for user intervention")},
+        {"autofix",     N_("in script mode, fix instead of abort when asked")},
         {"version",     N_("displays the version")},
         {"align=[none|cyl|min|opt]", N_("alignment for new partitions")},
         {NULL,          NULL}
 };
 
 int     opt_script_mode = 0;
+int     opt_autofix_mode = 0;
 int     pretend_input_tty = 0;
 int     opt_machine_mode = 0;
 int     disk_is_modified = 0;
@@ -2200,6 +2203,7 @@ while (1)
                 case 'l': list = 1; break;
                 case 'm': opt_machine_mode = 1; break;
                 case 's': opt_script_mode = 1; break;
+                case 'f': opt_autofix_mode = 1; break;
                 case 'v': version = 1; break;
                 case 'a':
                   alignment = XARGMATCH ("--align", optarg,
diff --git a/parted/ui.c b/parted/ui.c
index 7b5374d..2e43896 100644
--- a/parted/ui.c
+++ b/parted/ui.c
@@ -643,6 +643,12 @@ exception_handler (PedException* ex)
         if (!option_get_next (ex->options, opt))
                 return opt;
 
+        /* script-mode and autofix? */
+        int autofix_is_an_option = (ex->options & PED_EXCEPTION_FIX);
+        if (opt_script_mode && opt_autofix_mode && autofix_is_an_option) {
+                return PED_EXCEPTION_FIX;
+        }
+
         /* script-mode: don't handle the exception */
         if (opt_script_mode || (!isatty (0) && !pretend_input_tty))
                 return PED_EXCEPTION_UNHANDLED;
diff --git a/parted/ui.h b/parted/ui.h
index 6192ee5..ff754a2 100644
--- a/parted/ui.h
+++ b/parted/ui.h
@@ -88,6 +88,7 @@ extern void print_using_dev (PedDevice* dev);
 
 /* in parted.c */
 extern int	opt_script_mode;
+extern int	opt_autofix_mode;
 extern int	pretend_input_tty;
 
 extern void print_options_help ();
-- 
2.25.1