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"' \;
Tag: 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
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
Ubuntu on the Acer Nitro 5
[updated June 2021] [June 2021] New chapter about Ubuntu 20.04 The Acer Nitro 5 is an interesting breed; decent computing power, a mid-range SSD, a large screen with high contrast, a decent and solid keyboard with good haptics at an ok price - but will it run Ubuntu 18.04? (yes, it will - also with … Continue reading Ubuntu on the Acer Nitro 5
Resetting a PCI device
The Wi-Fi adapter on my VivoBook 17 has been acting up under Ubuntu 18.04 LTS insofar that at a random point in time, possibly accelerated by power saving features, the Wi-Fi will stop working with suspicious syslog entries: ath10k_pci 0000:03:00.0: failed to wake target for read32 at 0x0003a028: -110 The usual tricks (suspend/resume, reload driver, … Continue reading Resetting a PCI device
A crazy server recovery
If you're a seasoned server administrator then this post will boring beyond oblivion to you; the ingredients: a headless server (no screen, keyboard)years of personal backups on a linux software RAIDa botched system upgradehappy ending The pretext Several years ago I bought an HP Proliant microserver on discount and set up a NAS with Ubuntu … Continue reading A crazy server recovery
