alas for thee, EVMS

Today I needed to shrink an LVM2 volume group that lives on top of an encrypted
partition.  Here are the steps I had to go through:

1. Run cryptsetup to open the encrypted container.
2. Run lvmdiskscan to detect the new volume group.
3. Run vgchange to activate the volume group.
4. Check the file system on the volume I wanted to shrink.
5. Shrink the file system on the volume.
6. Shrink the logical volume.
7. Resize the file system again, to make it match the size of the logical
volume, which I made a little bigger than the file system to avoid trouble.
8. Shrink the physical volume.
9. Shrink the encrypted container.
10. Run cfdisk to fix the partition table.

That is 8 different commands, each with its own set of options and, of course,
all measuring sizes in different units:  MB/GB (are those MB or MiB?), sectors
(512 B), and extents (4 MB).

Writing in a review of EVMS for OSNews about 3 years ago, I described exactly
this situation, which I'd hoped never to find myself in again:

"Have you ever had to shrink a disk partition and the file system that lived on
it? If you haven't, take it from me: it requires great care and carries a high
risk of destroying your data. You have to shrink first the file system and then
the partition, paying careful attention that the numbers and sizes of blocks are
the same in both operations. Different commands are required to resize the
partition and each type of file system, with different options, and sometimes
different default block sizes. Issue a wrong command, and your data is history.
This is exactly the sort of dangerous and error-prone task that software should
handle for us, and EVMS does. Just tell it to shrink (or expand) a volume, and
it takes care of the details. The task is both easier and safer."

This was always my favorite feature of EVMS, that it freed us from the danger
and drudgery of the kind of procedure I described above.  To this day I haven't
found any other software that matches it in that regard.  What a shame that it's
been abandoned.

Andrew.


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