USB harddrive not showing on USB 3.0 port

A particular USB harddrive won't show up in the device list under Ubuntu 18.04 when connected to a USB 3.0 port of the HP proliant microsever gen8 though it will show up when connected to a USB 2.0 port. The symptoms are that the drive won't list with fdisk -l nor how up under /dev/sdX. … Continue reading USB harddrive not showing on USB 3.0 port →

Monitoring input audio with Ubuntu

Monitoring an audio source is a term audio folks use to say that they send the signal from an audio input source (eg. line in or microphone) to an auxiliary audio output (eg. headphones) so that they can listen to the input signal in real time. Windows 10 allows this out of the box, it's … Continue reading Monitoring input audio with Ubuntu →

Skype and VLC cannot use v4l2loopback video device

I'm playing around with using DSLR cameras as webcams with gphoto (CLI to cameras over USB) and v4l2loopback (dummy video devices), which works with OBS but neither Skype nor VLC which will either show a black image or fail with an error message. Running VLC in verbose mode and digging a bit around showed that … Continue reading Skype and VLC cannot use v4l2loopback video device →

Constant disk access with ext4 caused by kmmp

I don't know how I never noticed this, but the mechanical hard disks in the perfect NAS emit a clicking noise at regular intervals that never stops. The NAS runs Ubuntu 18.04 server, an md software RAID 6 with dmcrypt on top, formatted with ext4. Disk I/O is way too low to show anything useful … Continue reading Constant disk access with ext4 caused by kmmp →

First write operation to large ext4 file system is slow

I'm running a large (>20TB) ext4 file system and noticed that the first substantial write operation after mounting is very slow and involves plenty of drive activity. The reason seems to be some memory structure initialisation as described here: https://linux-ext4.vger.kernel.narkive.com/SUFNE520/ext4-slow-performance-on-first-write-after-mount The workaround is thankfully as simple as running this command in a script after mounting … Continue reading First write operation to large ext4 file system is slow →