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mke2fs: prompt for user verification for "-S" 

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@dilger.ca>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
test-maint
Andreas Dilger 2015-06-19 21:34:02 -04:00 committed by Theodore Ts'o
parent 59707c1b58
commit a6eeac1ceb
2 changed files with 22 additions and 9 deletions
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24
misc/mke2fs.8.in
View File

@ -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

7
misc/mke2fs.c
View File

@ -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