sfdisk: improve --wipe functionality

* always (except --wipe=never) wipe old partition tables
* improve warn messages
* improve man page

Addresses: https://github.com/karelzak/util-linux/issues/410
Signed-off-by: Karel Zak <kzak@redhat.com>

diff --git a/disk-utils/sfdisk.8 b/disk-utils/sfdisk.8
index de619bc857ca8c77d3509965696cecaf11ce809a..e8ecf48384af0c78b399fb50409e7adb143b2b49 100644 (file)
--- a/disk-utils/sfdisk.8
+++ b/disk-utils/sfdisk.8
@@ -226,9 +226,11 @@ This option allows to edit for example a hybrid/protective MBR on devices with G
 Wipe filesystem, RAID and partition-table signatures from the device, in order
 to avoid possible collisions.  The argument \fIwhen\fR can be \fBauto\fR,
 \fBnever\fR or \fBalways\fR.  When this option is not given, the default is
-\fBauto\fR, in which case signatures are wiped only when in interactive mode.
-In all cases detected signatures are reported by warning messages
-before a new partition table is created.  See also
+\fBauto\fR, in which case signatures are wiped only when in interactive mode;
+except the old partition-table signatures which are always wiped before create
+a new partition-table if the argument \fIwhen\fR is not \fBnever\fR. In all
+cases detected signatures are reported by warning messages before a new
+partition table is created.  See also
 .BR wipefs (8)
 command.
 

diff --git a/disk-utils/sfdisk.c b/disk-utils/sfdisk.c
index eedaa39d9dbc252b3ac557cd45c54054f80979aa..cf6d96df59e7db5f6bae3ae862c491cc4da5ca51 100644 (file)
--- a/disk-utils/sfdisk.c
+++ b/disk-utils/sfdisk.c
@@ -1462,6 +1462,36 @@ static int ignore_partition(struct fdisk_partition *pa)
        return 0;
 }
 
+static void follow_wipe_mode(struct sfdisk *sf)
+{
+       int dowipe = sf->wipemode == WIPEMODE_ALWAYS ? 1 : 0;
+
+       if (sf->interactive && sf->wipemode == WIPEMODE_AUTO)
+               dowipe = 1;     /* do it in interactive mode */
+
+       if (fdisk_is_ptcollision(sf->cxt) && sf->wipemode != WIPEMODE_NEVER)
+               dowipe = 1;     /* always wipe old PT */
+
+       fdisk_enable_wipe(sf->cxt, dowipe);
+       if (sf->quiet)
+               return;
+
+       if (dowipe) {
+               if (!fdisk_is_ptcollision(sf->cxt)) {
+                       fdisk_info(sf->cxt, _("The old %s signature will be removed by a write command."),
+                                       fdisk_get_collision(sf->cxt));
+                       fputc('\n', stderr);
+               }
+       } else {
+               fdisk_warnx(sf->cxt, _(
+                       "The old %s signature may remain on the device. "
+                       "It is recommended to wipe the device with wipefs(8) or "
+                       "sfdisk --wipe, in order to avoid possible collisions."),
+                       fdisk_get_collision(sf->cxt));
+               fputc('\n', stderr);
+       }
+}
+
 static int wipe_partition(struct sfdisk *sf, size_t partno)
 {
        int rc, yes = 0;
@@ -1612,25 +1642,8 @@ static int command_fdisk(struct sfdisk *sf, int argc, char **argv)
                        fputs(_(" OK\n\n"), stdout);
        }
 
-       if (fdisk_get_collision(sf->cxt)) {
-               int dowipe = sf->wipemode == WIPEMODE_ALWAYS ? 1 : 0;
-
-               fdisk_warnx(sf->cxt, _("Device %s already contains a %s signature."),
-                       devname, fdisk_get_collision(sf->cxt));
-
-               if (sf->interactive && sf->wipemode == WIPEMODE_AUTO)
-                       dowipe = 1;     /* do it in interactive mode */
-
-               fdisk_enable_wipe(sf->cxt, dowipe);
-               if (dowipe)
-                       fdisk_warnx(sf->cxt, _(
-                               "The signature will be removed by a write command."));
-               else
-                       fdisk_warnx(sf->cxt, _(
-                               "It is strongly recommended to wipe the device with "
-                               "wipefs(8), in order to avoid possible collisions."));
-               fputc('\n', stderr);
-       }
+       if (fdisk_get_collision(sf->cxt))
+               follow_wipe_mode(sf);
 
        if (sf->backup)
                backup_partition_table(sf, devname);
@@ -1728,6 +1741,9 @@ static int command_fdisk(struct sfdisk *sf, int argc, char **argv)
                                        fdisk_warnx(sf->cxt, _(
                                          "Failed to apply script headers, "
                                          "disk label not created."));
+
+                               if (rc == 0 && fdisk_get_collision(sf->cxt))
+                                       follow_wipe_mode(sf);
                        }
                        if (!rc && partno >= 0) {       /* -N <partno>, modify partition */
                                rc = fdisk_set_partition(sf->cxt, partno, pa);