What user sjr said on https://stackoverflow.com/questions/4643438/how-to-search-contents-of-multiple-pdf-files find /path -name '*.pdf' -exec sh -c 'pdftotext "{}" - | grep --with-filename --label="{}" --color "your pattern"' \;
Category: linux
dm-raid and dm-integrity performance issue
I'm experimenting with protecting the perfect NAS RAID setup against bit rot (silent data corruption in long storage) and recently experimented with dm-integrity towards that end. The idea is to add checksums on the block level to each hard disk so that data corruption shows up as an I/O error do dm-raid, which would then … Continue reading dm-raid and dm-integrity performance issue
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
Higher frame rate with Microsoft LifeCam and Linux
The Microsoft LifeCam is a versatile USB Webcam family which is supported well in Ubuntu Linux. Unfortunately it records HD videos only at low fps, but there is a workaround to get high resolution with 30 fps. Install guvcviewOpen guvcview, switch to the Video Controls tab and pick the LifeCamSelect 30/1 fps in the Frame … Continue reading Higher frame rate with Microsoft LifeCam and Linux
Nautilus browsing large windows share is slow
When browsing large windows (samba) shares with Ubuntu Nautilus (that's the equivalent of the Windows File Explorer) I observed that shares which include many files and directories (a few hundred) take a few seconds to browse over WiFi, but almost instantly display over a fast LAN. A similar difference in speed is noticeable when searching … Continue reading Nautilus browsing large windows share is slow
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
Building the perfect, cheap DIY NAS
This post was extensively discussed on Hacker News.Alex Buznik, nas.net.ua kindly provided a two-part Russian translation: part1 and part2. This post discusses hardware considerations, installing Linux, setting up software RAID, robustness and dealing with data corruption. I've been running for a decade a self-built NAS at home, so I thought I'd write down my experience … Continue reading Building the perfect, cheap DIY NAS
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
