OS/Internet

Update expired keys

Sometimes apt-get update doesn’t work because keys have expired (e.g. The following signatures were invalid: EXPKEYSIG XXX). To update a key:

sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys XXX

(French) Accents in Gnome Ubuntu

I use the international layout with dead keys:

Settings -> Region & Language -> Input Sources -> + -> English (United States) -> English (intl., with AltGr dead keys)

An accented letter can be “spelled out” with, for example, AltGr+Super+' e. Some accented letters can be inserted directly with AltGr, e.g. AltGr+e. Inspired by this post, I modified the default accented letters to use grave/circumflex accents and cedilla. In /usr/share/X11/xkb/symbols/us I added to the xkb_symbols “altgr-intl” section:

   key <AD04> { [ r, R, egrave,       Egrave      ] };
   key <AD05> { [ t, T, ecircumflex,  Ecircumflex ] };
   key <AD02> { [ w, W, ediaeresis,   Ediaeresis  ] };
   key <AD06> { [ y, Y, ucircumflex,  Ucircumflex ] };
   key <AD07> { [ u, U, ugrave,       Ugrave      ] };
   key <AD08> { [ i, I, icircumflex,  Icircumflex ] };
   key <AD09> { [ o, O, ocircumflex,  Ocircumflex ] };
   key <AC01> { [ a, A, agrave,       Agrave      ] };
   key <AC02> { [ s, S, acircumflex,  Acircumflex ] };
   key <AB03> { [ c, C, ccedilla,     Ccedilla    ] };

On the cloud

I use Nextcloud which offers a free tier with 2 Gb (for most providers). It also has an Ubuntu software and Android app that can sync a specific folder. I use it to synchronize the articles I read and annotate between my tablet and computer(s) (see the “Zotero” section below).

1. Sign up for a free 2Gb server at https://nextcloud.com/sign-up/ (for example The Good Cloud)
2. Download the AppImage for Ubuntu from https://nextcloud.com/install/
   • An AppImage is some kind of binary: make it executable using chmod +x and place in your PATH.
3. When logging in to the Nexcloud app, there is an option to select exactly which folder(s) to sync.
4. On the tablet, use the Nexcloud Android App from F-Droid or Google Play.
   • Note: the app is buggy on my tablet. An alternative solution is FolderSync which is slow (checks all the files!) but works. Another “alternative” is to sync directly using Syncthing (see below)

Sync in real time with Syncthing

Syncthing can be easily setup to synchronize specific folders. It needs to be running on all the devices but it’s fast and avoids using a cloud hosting service.

On Ubuntu, I run it using Docker with:

docker run --network=host -v `pwd`:/var/syncthing --hostname=my-syncthing syncthing/syncthing:latest

The GUI can then be openened in the browser, by default at http://127.0.0.1:8384/.

The Syncthing Androids app is available on F-Droid and Google Play.

[DEPRECATED?] Before: sync a specific Google Drive folder on Ubuntu

This might not work anymore. Last time I tried to use it, I was confused by an error and ended up switching to Nextcloud (see above).

I use grive and followed these instructions.

To install:

sudo apt-add-repository ppa:nilarimogard/webupd8
sudo apt-get update
sudo apt-get install grive

To configure in a directory DIR, syncing the Drive folder “ArticlesPDF”:

cd DIR
grive -a -s ArticlesPDF

In the future just sync by running the following command (in the DIR folder):

grive -s ArticlesPDF

I usually try with the --dry-run option first because there are some glitches sometimes.

Since very recently (~Nov 2019) another step is necessary:

1. Create a API key on https://console.developers.google.com/apis/library following those instructions.
2. Run with grive -s zotero-library --id "<ID.apps.googleusercontent.com>" --secret "<SECRET>" (eventually add -a to configure).

[DEPRECATED] Before: sync PDFs between Mendeley and Google Drive

Before switching to Zotero, I used Mendeley. I was still syncing my annotated PDFs between my tablet and computer. I had described this approach in this post.