I tried to dual-boot Ubuntu with Win8.1 but at installation by mistake selected LVM and then did reboot. All my partitions now in Ubuntu Live CD shows as single LVM. How can I recover the data of old Win8.1?
You may want to try using TestDisk and PhotoRec from http://www.cgsecurity.org/ to recover your data. Depending on how corrupted the data is, it might be possible to recover most of your data including the partition table. Worst case, you may be able to at least recover your files partially.
It appears you may have selected an option to reformat your partition table / partitions as LVM instead of the usual MBR/UEFI format if the former, or instead of a FAT32/NTFS system if the latter. This means that the part of the hard drive which Windows 8.1 used for keeping track of where each part of which file is (let's call it a file index) might have been corrupted to a varying degree.
This means that the files may be still there (or partially there, if the LVM format process overwrote the part of the hard drive where a file or a file fragment was stored), just not in a format which your operating system can recognise immediately as the OS depends on the index to work. PhotoRec tries hard to find files without using an index, which means that:
- The folder structure and file names might not be preserved. This means that the items may unordered, all placed in the same folder upon recovery and with auto-generated names (or partially-recovered names in some instances), even if the files themselves are recovered in their entirety.
- Some files may not be contiguous (i.e. occupying a single continuous chunk of hard drive space), which is not normally a problem as the index stores the information on which chunks of the file are located where. Parts of the index may be missing, so some files may be recovered as cut-up in several pieces.
- Before you begin recovery, you must select which file types you want PhotoRec to look for. File detection is done using pattern matching, so it may produce false positives/negatives. Pick carefully.
- Try TestDisk first. It doesn't do such a deep scan as PhotoRec, but it may be able to recover some partition table/file system structures and you might not need to do a PhotoRec scan.