- Shut down an external hard drive
- Switch keyboard layout (X11)
- Control external displays
- Kill the app which listens own a given port
- Increase the number of watchers for a "live reload" app
- Clear node_modules (Node.js)
- NFS with Linux server and MacOS client
- Mounting Windows 10 WSL2 virtual disk from Linux
Even if you did unmount all the volumes on an external drive, the drive itself is probably still turned on. This will shut it down:
sudo udisksctl power-off -b /dev/sdb
As a French guy, I use an US keyboard (Qwerty) but often have to switch between regular US layout and international US layout.
Switch to regular US:
setxkbmap -layout us
Switch to international US:
setxkbmap -layout us -variant intl
List all displays:
xrandr
On my desktop PC with an HDMI and a VGA monitor, I get this output:
Screen 0: minimum 320 x 200, current 4480 x 1440, maximum 8192 x 8192
HDMI-1 disconnected primary (normal left inverted right x axis y axis)
HDMI-2 connected 2560x1440+0+0 (normal left inverted right x axis y axis) 597mm x 336mm
2560x1440 59.95*+
1920x1080 60.00 50.00 59.94
1920x1080i 60.00 50.00 59.94
1680x1050 59.88
1600x900 60.00
1280x1024 75.02 60.02
1280x800 59.91
1152x864 75.00
1280x720 60.00 50.00 59.94
1024x768 75.03 60.00
832x624 74.55
800x600 75.00 60.32
720x576 50.00
720x576i 50.00
720x480 60.00 59.94
720x480i 60.00 59.94
640x480 75.00 60.00 59.94
720x400 70.08
DP-1 disconnected (normal left inverted right x axis y axis)
HDMI-3 disconnected (normal left inverted right x axis y axis)
DP-2 connected 1920x1080+2560+0 (normal left inverted right x axis y axis) 510mm x 287mm
1920x1080 60.00*+
1680x1050 59.95
1280x1024 60.02
1440x900 59.89
1280x720 60.00
1024x768 60.00
800x600 60.32
640x480 59.94
720x400 70.08
Hence my displays are HDMI-2 (HDMI) and DP-2 (VGA).
Turn a display off:
xrandr --output DP-2 --off
Turn it back on, to the right of the HDMI monitor:
xrandr --output DP-2 --right-of HDMI-2 --auto
When you develop with Node.js and interrupt an app (e.g. HTTP server) with Ctrl+C, it sometimes happens that the port it was listening on isn't freed at once. In that case, knowing which port it is, you can kill the process blocking the port like so (here the port is TCP 4000):
fuser -k 4000/tcp
Front-end frameworks, and Nodemon (for Node.js), provide a "live reload" feature that reloads the app when one of its file is modified. This consumes system resources (file watchers). You'll most likely stumble on this error message after a while:
ENOSPC: System limit for number of file watchers reached
This solves the problem once and for all:
echo fs.inotify.max_user_watches=524288 | sudo tee -a /etc/sysctl.conf && sudo sysctl -p
If you're a Node.js developer and are low on disk space, you might want to remove node_modules folders from some projects.
This will clear all of them under the current directory (beware):
find . -name "node_modules" -type d -prune -exec rm -rf '{}' +
Source: https://rtmccormick.com/2018/01/10/clear-node-modules-folders-recursively-mac-linux/
Linux Server - Append this to /etc/exports:
/media/nfs 192.168.1.0/24(rw,sync,insecure,all_squash,no_subtree_check)
Options are well explained here: https://blog.natetodd.com/mount-linux-nfs-share-from-macos-10-13-high-sierra/
Mount on MacOS client (create /media/nfs first):
sudo mount -o resvport,rw -t nfs 192.168.1.67:/media/nfs /media/nfs
On a dual-boot Windows/Linux computer, you might want to access the WSL2 drive from Linux. It's an ext4 partition inside a .vhdx file. Now how to find it? An official Microsoft tutorial has a section titled Mount a VHD in WSL giving a hint: the ext4.vhdx file is located under C:\Users\[user]\AppData\Local\Packages\[distro]\LocalState\[distroPackageName].
Since my C: drive is mounted as /media/c on my Linux system, here's the actual path:
/media/c/Users/Ben/AppData/Local/Packages/CanonicalGroupLimited.Ubuntu20.04onWindows_79rhkp1fndgsc/LocalState/ext4.vhdx
Now, how can I attach a VHDx or VHD file in Linux?. Just follow the instructions!
sudo apt-get install libguestfs-tools
sudo mkdir /media/wsl2
sudo guestmount --add /media/c/Users/Ben/AppData/Local/Packages/CanonicalGroupLimited.Ubuntu20.04onWindows_79rhkp1fndgsc/LocalState/ext4.vhdx --inspector --ro /media/wsl2
Only drawback here is I need sudo privileges to just read anything under /media/wsl2! To be continued...