WangLu's Notes

[UPDATE] Later I was able to successfully migrate an amd64 Ubuntu server to Debian, following the same procedure. I had a Ubuntu 22.04.3 on a Raspberry Pi 4. Recently I decided to switch it to Debian 12.5 in-place . Mostly I was following this script: https://github.com/alexmyczko/autoexec.bat/blob/master/config.sys/ubuntu-deluxe   It worked surprisingly well, however, the system was eventually broken (unsurprisingly) near the end, when I tried to upgrade the kernel. I tried to fix initramfs by copying dtbs files, which seemed to work. Some references: https://qiita.com/takasan/items/ef93be9e9d3f791eee66 https://bugs.launchpad.net/ubuntu/+source/flash-kernel/+bug/2012750 But the kernel did not load after reboot. Reverting /boot/config.txt didn't help. Then I downloaded a Debian image and replaced only the boot partition of the micro SD card. This time the kernel was able to boot, but it couldn't load the filesystem. I modified cmdline.txt, replaced "root=LABEL=RASPIROOT...

最近忽然想试试restic，看看几年后有什么变化。 实际上之前做数据备份计划时大致比较了rclone和restic，经过简单测试以后决定用rclone。当时对restic印象一般，主要考虑两点： 1. restic是专有格式，没有程序文件的话无法访问备份的数据。 2. 之前测试restic的时候莫名其妙备份仓库数据有损坏。 不过用了rclone几年以后发现第一条对rclone的加密仓库也成立。 测试数据 我挑选了一些数据，主要是图片和视频，分别用restic和rclone备份。 数据包含121191个文件，总共3.869TiB。由于ZFS压缩，实际占用磁盘3.6TiB。 测试环境 原始数据保存在一台Ubuntu 22.04.3的机器上，文件系统使用ZFS，启用zstd压缩，没有开启去重。 备份机器是一台群晖的机器，文件系统使用ext4. 两台机器用千兆网连接。在源机器上通过sftp访问备份机器。 restic备份 restic版本 restic 0.16.3 compiled with go1.21.6 on linux/amd64 备份仓库用默认参数创建。 最终是用了42个半小时结束。restic报告是3.655 TiB added to repo, 3.531 TiB stored on disk。备份仓库里最后有220568个文件。 我对结果比较惊讶，因为按这个结果看数据里有大概200GiB的重复数据块，我没想到有这么多。 不过最后占用磁盘大小跟原始文件在ZFS上的占用大小差不多，我也没想到。按理说已经去掉了200GiB文件，并且ZFS和restic我都用的zstd默认压缩率（也许它们的默认压缩率差很多？），我本来以为restic的仓库要再小点。 效率方面感觉42个多小时也太慢了点。不过我没找到性能瓶颈，很奇怪： - 两台机器CPU占用率都不高 - 源机器上CPU有8核，但是restic基本用不到200% - restic要调用ssh访问sftp，ssh大概也占用10%CPU - 网络数据量大概50MB/s，这感觉很低 - 磁盘也没有充分利用。ZFS那边我见过几百MB/s的速度，而群晖那边也显示磁盘使用率在一半左右。 所以最后我也没搞清楚原因。 还有一个问题，restic经常跑跑停停，有时看似完全休眠了一般，CPU，磁盘，网络完全没有动静，...

之前Google Reader挂了之后我基本一直用Feedly，后来也开始用Google Now看新闻，用Google Podcast听Podcast。 这几天决定切换到自己的服务器上，有若干原因： 越来越不喜欢Google Now的自动推送。感觉我的眼界越来越窄。 Feedly经常遇到收费功能。 Google Podcast要关闭了。 我正好也有服务器了 RSS抓取用的Tiny Tiny RSS，这个之前就搭建好了，作为Feedly的备份。最近升级发现docker compose文件有若干变化，数据库版本也变了，稍微折腾了一下。 类似的还有几个 Miniflux FreshRSS NewBlur 不过这些其实都大同小异。主要Tiny Tiny RSS导入导出备份都挺方便。 手机端用的Feedme，直接支持Tiny Tiny RSS的API，也可以放Podcast 我的RSS源都很老了，有好多都没法用了，Feedly也不提示我。发现了两个不错的RSS网站 https://docs.rsshub.app/ https://feedx.net/ Podcast回头也得整理一下，不过目前问题不大。

The Video A Bit Background Thanks to Youtube's algorithms, I got to watch  this video  again after many years. The video, made in 1994, explains the sphere eversion problem and visualizes one solution: Thurston's corrugations. More information can be found in the following links: 1 , 2 , 3 . There is also an HD version . The animations in the video are really fascinating. I figured it'd be a good excercise to recreate it with Blender, especially with geometry nodes. However I immediately got stuck after 20 minutes, because I had no clue how everything works. Luckily I found a port  of the original source code. (The original source code  seems no longer available). The author also created a nice video . I'll refer this version as  mathIsART's version. I also found another port , which I'll refer to as McGuffin's version. Mostly I studied mathIsART's version, and occasionally used McGuffin's version as reference. The code was really fun to read, and I ...