The problem#

Last week, I shared a script which continuously backed up game saves whenever the game saved. The result is a series of directories that contain snapshots of the game saves from every autosave. But to view this data, we really want a list of unique files in order marked with the time they were created.

The solution#

The following will create symbolic links to the unique files named after their modification date:

for i in /tank/factorio/.zfs/snapshot/*/*.zip
do
  ln -sf "$i" "$(stat --printf=%y "$i").zip"
done

or if you want a custom date format, you can use date:

  ln -sf "$i" "$(date -r "$i" +%Y-%m-%d_%H-%M-%S).zip"

Alternatively, the following will just list the unique files with their timestamps:

find /tank/factorio/.zfs/snapshot/ -printf "%T+ %p\n" \
    | sort | uniq --check-chars=30

The details#

Introduction#

Factorio is a sandbox automation and logistics game notable for, among other things, very good support for mods. The developers often go out of their way to support features and fix bugs that only affect mods.

I've only just started to dip my toes in the world of Factorio modding, so I'm definitely no authority on the topic. But this post will be about things that weren't obvious to me starting out.

Resources#

As I said, modding is very well supported, which includes comprehensive documentation and tutorials. One detail I'd call out is that I recommend installing FMTK, which provides IDE tooling for writing Factorio mods, including a VS Code extension (don't worry, there's a Vim mode for VS Code). Also you will probably spend a lot of time looking at the log file. Additionally, you can find lots of examples by looking at the many existing mods; a lot them have links to source code repositories from their mod pages, but even if they don't, you can just download them and unzip them.

If you have a question that can't be answered by those resources or a web search, you can ask for help on the modding forum or the #modding-help channel of the official Factorio Discord.

Other tips#

The problem#

I will often make copies of important files onto multiple devices, and then later make backups of all of those devices onto the same drive. At which point, I now have multiple redundant copies of those files within my backup. Tools like rdfind, fdupes, and jdupes exist to deal with the general problem of searching a collection of files for duplicates efficiently, but none of them support only checking if files are identical if their filenames and/or paths match, so they end up doing a lot of extra work in this case.

The solution#

Download the script I wrote, hardlink-dups-by-name.sh and run it as follows:

hardlink-dups-by-name.sh a_backup/ another_backup/

Then all files like a_backup/some/path that are identical to the corresponding file another_backup/some/path will get hard-linked together so there will only be one copy of the data taking up space.

The details#