Prompt for user verification before rewriting the filesystem
superblocks using the "-S" (super-only) option. This should
not normally be used at all, so adding the extra verification
will probably save a few user filesystems in the future. Since
this is something that should only be done in rare cases under
user supervision, wait for user input rather than proceeding
automatically after a timeout.
Update the mke2fs man page to more fully explain the many
dangers of this option.
Signed-off-by: Andreas Dilger <adilger@xxxxxxxxx>
---
misc/mke2fs.8.in | 24 ++++++++++++++++--------
misc/mke2fs.c | 7 ++++++-
2 files changed, 22 insertions(+), 9 deletions(-)
diff --git a/misc/mke2fs.8.in b/misc/mke2fs.8.in
index 1002eae..2a50ad2 100644
--- a/misc/mke2fs.8.in
+++ b/misc/mke2fs.8.in
@@ -619,18 +619,26 @@ kernels only support revision 0 filesystems. The default is to
create revision 1 filesystems.
.TP
.B \-S
-Write superblock and group descriptors only. This is useful if all of
+Write superblock and group descriptors only. This is an extreme
+measure to be taken only in the very unlikely case that all of
the superblock and backup superblocks are corrupted, and a last-ditch
-recovery method is desired. It causes
+recovery method is desired by experienced users. It causes
.B mke2fs
-to reinitialize the
-superblock and group descriptors, while not touching the inode table
-and the block and inode bitmaps. The
+to reinitialize the superblock and group descriptors, while not
+touching the inode table and the block and inode bitmaps. The
.B e2fsck
program should be run immediately after this option is used, and there
-is no guarantee that any data will be salvageable. It is critical to
-specify the correct filesystem blocksize when using this option,
-or there is no chance of recovery.
+is no guarantee that any data will be salvageable. Due to the wide
+variety of possible options to
+.BR mke2fs
+that affect the on-disk layout, is critical to specify exactly the same
+the same format options, such as blocksize, fs-type, feature flags, and
+other tunables when using this option, or the filesystem will be further
+corrupted. In some cases, such as filesystems that have been resized,
+or have had features enabled after format time, it is impossible to
+overwrite all of the superblocks corretly, and at least some filesystem
+corruption will occur. It is best to run this on a full copy of the
+filesystem so other options can be tried if this doesn't work.
.\" .TP
.\" .BI \-t " test"
.\" Check the device for bad blocks before creating the file system
diff --git a/misc/mke2fs.c b/misc/mke2fs.c
index a14e62e..e49ad04 100644
--- a/misc/mke2fs.c
+++ b/misc/mke2fs.c
@@ -2771,9 +2771,14 @@ int main (int argc, char *argv[])
}
if (super_only) {
+ check_plausibility(device_name, CHECK_FS_EXIST, NULL);
+ printf(_("%s may be further corrupted by superblock rewrite\n"),
+ device_name);
+ if (!force)
+ proceed_question(proceed_delay);
fs->super->s_state |= EXT2_ERROR_FS;
fs->flags &= ~(EXT2_FLAG_IB_DIRTY|EXT2_FLAG_BB_DIRTY);
- /*
+ /*
* The command "mke2fs -S" is used to recover
* corrupted file systems, so do not mark any of the
* inodes as unused; we want e2fsck to consider all
--
1.7.3.4
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