A folder named ~/.cache/kioexec/krun/13821_0/ already exists

2017-12-09 jj5 – TODO: document this on my blog…

On Debian GNU/Linux 9.1 (stretch) when I try to open an *.desktop (application/x-desktop) link in a browser I get:

A folder named ~/.cache/kioexec/krun/13821_0/ already exists.

Searching for:

A folder named kioexec krun already exists

turned up diddly squat.

I solved the issue (for me) by changing:

System Settings -> Personalization -> Applications -> Default Application s-> Web Browser

from:

Open http and https URLs in an application based on the contents of the URL

to:

Open http and https URLs in the following browser: firefox

Installing .NET on Debian 9

After installing Visual Studio Code I followed the instructions from .NET Tutorial – Hello World in 10 minutes, basically:

wget -qO- https://packages.microsoft.com/keys/microsoft.asc | gpg --dearmor > microsoft.asc.gpg
sudo mv microsoft.asc.gpg /etc/apt/trusted.gpg.d/
wget -q https://packages.microsoft.com/config/debian/9/prod.list
sudo mv prod.list /etc/apt/sources.list.d/microsoft-prod.list
sudo chown root:root /etc/apt/trusted.gpg.d/microsoft.asc.gpg
sudo chown root:root /etc/apt/sources.list.d/microsoft-prod.list

Then:

sudo apt-get update
sudo apt-get install dotnet-sdk-2.1

Then for example to create a new console project:

dotnet new console -o myApp
cd myApp

I ended up reading MICROSOFT SOFTWARE LICENSE TERMS for the MICROSOFT .NET LIBRARY which included this doozy:

The software may collect information about you and your use of the software, and send that to Microsoft.

Ah, Microsoft. You haven’t changed.

I found some notes about how to disable telemetry:

Telemetry
———
The .NET Core tools collect usage data in order to help us improve your experience. The data is anonymous and doesn’t include command-line arguments. The data is collected by Microsoft and shared with the community. You can opt-out of telemetry by setting the DOTNET_CLI_TELEMETRY_OPTOUT environment variable to ‘1’ or ‘true’ using your favorite shell.

Read more about .NET Core CLI Tools telemetry: https://aka.ms/dotnet-cli-telemetry

I have added the opt-out environment variable via jj5-bin.

Enabling TRIM in Debian fstab for ext4 file-system on Samsung SSD 960 EVO NVMe M.2

So I was trying to find why in my Debian 9 system my SATA drives are called SCSI devices, and I was reading Why my SATA drive is identified as a SCSI device in Device Manager where I read:

The Intel Rapid Storage driver version 12.6 (Released in March 2013) and newer versions classify all drives as SCSI devices for uniformity. This (and later) versions of the driver also allow for TRIM support (Allows for management of data blocks no longer in use) in SSD drives in RAID 0 arrays and other flexibility in operation of storage devices.

So I’d never heard of “TRIM” so I searched for that and found the Wikipedia Trim (computing) article, but Why SSD TRIM Support is So Important and How to Enable It caught my eye, because, “important” you say?

So that article about the importance of TRIM was for Windows, so I searched again and found How to properly activate TRIM for your SSD on Linux: fstrim, lvm and dm-crypt which suggested things were a bit complicated for LVM (and MD RAID?).

I ended up reading How to set up SSD raid and TRIM support? which sent me to Re: Best way (only?) to setup SSD’s for using TRIM which argued that perhaps TRIM configuration wasn’t necessary at all.

It was then I realised that I probably don’t care about TRIM on my MD RAID SSD drives, but I probably do on my M.2 SSD, which isn’t using MD RAID, but which gets massive tgz files written to it and deleted from it every day. So some more searching and I found Samsung SSD 960 EVO NVMe M.2 Review: Ultra Fast, Affordable Storage which said TRIM was supported:

Supporting features: TRIM (Required OS support), Garbage Collection, S.M.A.R.T

So then I found Enable TRIM On SSD (Solid-State Drives) In Ubuntu For Better Performance which showed me how to enable TRIM in /etc/fstab. So the relevant fstab line was:

# /data/fast was on /dev/nvme0n1p1 during configuration
UUID=87bcc5fa-9261-404b-8bc7-a214f4651b49 /data/fast      ext4    noatime,discard 0       2

Note the ‘discard’ option, that’s where the magic happens.

So I unmounted and remounted the partition,

root@tact:/home/jj5# umount /data/fast
root@tact:/home/jj5# mount /data/fast

And dmesg indicated the discard option had been applied:

[34783.251592] EXT4-fs (nvme0n1p1): mounted filesystem with ordered data mode. Opts: discard

Now I guess we wait and see if my performance issues improve…

Airgap file-system

So I needed to create a file-system to house a handful of archive/backup tarballs (around 40 of them). I created an ext4 file-system with 100 inodes, like this:

# mkfs.ext4 -b 4096 -L airgap -m 0 -N 100 -v /dev/sdc1

Note: 100 inodes isn’t very many! Only supports up to 100 files/folders. Also note that 0% space is reserved for root. If you’re copying the above command make sure you replace /dev/sdc1 with an appropriate partition device.

Registering a systemd Service

So today I read How To Set Up VNC Server on Debian 8 which had a section on creating and registering the requisite scripts:

/usr/local/bin/myvncserver (make sure it’s executable with +x):

#!/bin/bash
PATH="$PATH:/usr/bin/"
DISPLAY="1"
DEPTH="16"
GEOMETRY="1024x768"
OPTIONS="-depth ${DEPTH} -geometry ${GEOMETRY} :${DISPLAY}"
case "$1" in
start)
/usr/bin/vncserver ${OPTIONS}
;;
stop)
/usr/bin/vncserver -kill :${DISPLAY}
;;
restart)
$0 stop
$0 start
;;
esac
exit 0

/lib/systemd/system/myvncserver.service:

[Unit]
Description=VNC Server example

[Service]
Type=forking
ExecStart=/usr/local/bin/myvncserver start
ExecStop=/usr/local/bin/myvncserver stop
ExecReload=/usr/local/bin/myvncserver restart
User=vnc

[Install]
WantedBy=multi-user.target

Then to register and start:

systemctl daemon-reload
systemctl enable myvncserver.service
systemctl start myvncserver.service

fs.inotify.max_user_watches

I had an error tailing my web logs, like this:

==> test.jj5.net-error.log <==
tail: inotify resources exhausted
tail: inotify cannot be used, reverting to polling

I found tail: “inotify resources exhausted” and/or “inotify cannot be used, reverting to polling: Too many open files” which said to edit /etc/sysctl.conf with:

#
# 2017-05-03 jj5 - SEE: tail inotify resources exhausted:
# https://nefaria.com/2014/08/tail-inotify-resources-exhausted/
#
fs.inotify.max_user_watches=1048576

Then to apply the new settings:

# sysctl -p

Disable middle mouse button (paste) on Debian KDE

Every now and again I will accidentally click the middle mouse button when I go to grab my mouse, and KDE will dump my clipboard buffer into a BASH shell. Not good. Could run something damaging if I’m unlucky. So see here for the solution. Basically run this to get the mouse device ID:

xinput list | grep 'id='

Then to edit e.g. device 10 to disable middle mouse button:

xinput set-button-map 10 1 0 3

To persist the changes add the set-button-map command to e.g. ~/.xstartup.

Or you can add a pointer configuration to ~/.Xmodmap like this:

pointer = 1 0 3 4 5 6 7 8 9 10

And make sure xmodmap is applied at start-up with an autostart file like e.g. ~/.config/autostart/mouse-config.desktop:

[Desktop Entry]
Type=Application
Name=mouse-config
Comment=Disables middle mouse button.
Exec=xmodmap /home/jj5/.Xmodmap