Fossil

with the previous script alone, at the expense of a lot of CPU time
during the backup. You may wish to switch to a less space-efficient
compression algorithm that takes less CPU power, such as [`lz4`][lz4].
Changing up the compression algorithm also provides some
security-thru-obscurity, which is useless on its own, but it *is* a
useful adjunct to strong encryption.


## Restoring From An Encrypted Backup

The “restore” script for the above fragment is basically an inverse of
it, but it’s worth showing it because there are some subtleties to take
care of. If all variables defined in earlier scripts are available, then
restoration is:

```
openssl enc -d -aes-256-cbc -pbkdf2 -iter 52830 -pass pass:"$pass" -in "$gd" |
    xz -d | sqlite3 ~/museum/restored-repo.fossil
```

We changed the `-e` to `-d` on the `openssl` command to get decryption,
and we changed the `-out` to `-in` so it reads from the encrypted backup
file and writes the result to stdout.

The decompression step is trivial.

The last change is tricky: we used `fossil sql` above to ensure that
we’re using the same version of SQLite to write the encrypted backup DB
as was used to maintain the repository, but unfortunately, we can’t get
the built-in SQLite shell to write a backup into an empty database.
Therefore, we have to either run the restoration against a
possibly-different version of SQLite and hope there are no
incompatibilities, or we have to go out of our way to build a matching
version of `sqlite3` before we can safely do the restoration.

Keep in mind that Fossil often acts as a dogfooding project for SQLite,
making use of the latest features, so it is quite likely that a given
random `sqlite3` binary in your `PATH` may be unable to understand the
dump file created by the backup script!

[bu]:    /help?cmd=backup
[grcp]:  https://www.grc.com/passwords.htm
[hb]:    https://brew.sh
[hbul]:  https://docs.brew.sh/FAQ#what-does-keg-only-mean
[lz4]:   https://lz4.github.io/lz4/
[pbr]:   ./private.wiki
[rint]:  https://www.random.org/integers/?num=1&min=10000&max=100000&col=5&base=10&format=html&rnd=new