tech.notes

Debian Bluetooth headset problem

Fri, 08 Dec 2023 07:16:52 +0000

I had some problems to get my Bluetooth headset working with my Debian, the fault was kind of non informative.

In the end I found in some forum that it needs the following lib.

libspa-0.2-bluetooth

I found this here.

Connection Failed: br-connection-profile-unavailable

This was the only fault shown in the GUI.

Linux cp command with reflink

Tue, 11 Jul 2023 09:36:53 +0000

cp -pRv --reflink=auto /source/folder /destination/folder

copy files and directories
-p same as –preserve=mode,ownership,timestamps
-R, -r, –recursive
copy directories recursively
-v verbose, show what is going on.

–reflink[=WHEN]
control clone/CoW copies.

This just copied 169GB of files in 20 seconds. This only works on supported filesystems, so for example by “#Btrfs, #CIFS, #NFS 4.2, #OCFS2, #overlayfs, and #XFS”. See here.

Explainshell tells you this.

OCR all PDFs in a folder by cron

Mon, 03 Jul 2023 08:27:56 +0000

I will not write a long explanation, just this short one.

The cronjob looks like this:

* * * * * sh -c 'flock -n /tmp/my.lockfile /home/user/scripts/ocr_pdf_scan.sh'

This will start sh (a shell, just like bash) and run the command after -c. The command flock will create a lock-file, to prevent that this cron job is started while there is still the previous cron jobs running.

The cron job runs every minute, so in crontab it has * * * * * (five stars in front of the command).

Fix error "Failed to start DHCP Client Daemon" after upgrade to "Bullseye" on RaspberryPI

Sun, 04 Jun 2023 10:45:14 +0000

Important

This fix can be applied before the reboot after the upgrade from Buster to Bullseye, if you missed it you need a MicroSD card reader and some Linux computer (another RaspberryPI would do) to edit the file.

In the file

/etc/systemd/system/dhcpcd.service.d/wait.conf

there is a wrong path for the dhcpd, it has to be changed.

wrong (from buster):

/usr/lib/dhcpcd5/dhcpcd

correct and new on Bullseye:

/usr/sbin/dhcpcd

So you need to do this before the reboot, otherwise the RaspberryPi will not have a working WIFI or Ethernet connection after the reboot and will not allow you to login from remote by SSH.

Upgrade Raspberry Pi OS from Buster to Bullseye

Thu, 11 May 2023 13:07:58 +0000

So to upgrade Raspbian, as it was previously called, from Buster to Bullseye went smooth an easy, I tried this with some Pi2B (armhf 32Bit) and with a Pi4. These two are headless systems, so I don’t know if this works well for any systems with window managers.

Better run these commands in screen, so when the SSH connection is interrupted you can reconnect and resume your work.

Edit: For the update there is a culprit, it will cause a problem with dhcpd, so before the reboot 13. (was point 12. before I added the remark below) please check this post.

Resize a PDF to DIN A4 on CLI

Wed, 04 Jan 2023 17:18:11 +0000

Converts a PDF to DIN A4 paper size and centers the content of the input file on the new page without resizing it.

pdfjam --outfile file_a4.pdf --frame true --scale 1.0 --noautoscale true --paper a4paper file.pdf

Needs package “texlive-extra-utils” on Debian.

Adding Debian Buster Backports repo to RaspberryPi for tor

Fri, 05 Feb 2021 22:05:47 +0000

Add key

curl https://ftp-master.debian.org/keys/archive-key-10.asc | gpg --import
gpg --export DC30D7C23CBBABEE | apt-key add -

The fingerprint (DC30D7C23CBBABEE) given is the one that the first command outputs, which is the fingerprint of the key downloaded by curl.

2. Add repo

echo "deb http://deb.debian.org/debian buster-backports main" |sudo tee /etc/apt/sources.list.d/deb_buster_backports.list

run apt update/upgrade
Install tor, I did this by:

apt-get install -o Dpkg::Options::="--force-confold" -y tor

Debian for Raspberry Pi

Fri, 05 Feb 2021 21:59:23 +0000

Just some info, because the last time when I flashed an SD card I took #Raspbian only because I could not find the #Debian images as quick.

Infos about Debian for #Pi are here:
https://wiki.debian.org/RaspberryPi

Images:
https://raspi.debian.net/tested-images/

Some tips for settings, like #SSH on first boot (you need to add a key):
https://raspi.debian.net/defaults-and-settings/

Linux swap with dphys-swapfile

Mon, 20 Apr 2020 10:29:10 +0000

This is a solution for a #RaspberryPi, some #VPS without swap of some machine setup without swap where you need swap for something without wanting to fiddle with the drive partitions or so.

This is a quick and dirty “short manual” for #Debian based #Systemd environments (such as #Ubuntu, #Mint or #Raspbian).

First run this:

cat > dphys-swap.sh << EOF
#!/bin/bash
#~/up
apt-get install dphys-swapfile
echo "CONF_SWAPSIZE=2048"|tee -a /etc/dphys-swapfile
dphys-swapfile setup
dphys-swapfile swapon
systemctl restart dphys-swapfile.service
systemctl status dphys-swapfile.service
free -h
EOF

This will just create a short #bash #script with the needed commands to run to get #dphys setup and running. Please alter the number 2048 to your need, it is the size of the swap memory that will be setup. The size of the swap should most likely by equal to the real memory installed, sometimes twice the size seems to be a good choice too.

Debian based full updates in one command

Mon, 20 Apr 2020 10:24:40 +0000

I have this small script deployed on any of my #Debian based systems, it just does all the update, upgrade, dist-upgrade, autoremove and autoclean in one run.

#!/bin/sh

if [ $# -eq 0 ]; then
  sudo sh -c "apt-get update && apt-get upgrade && apt-get dist-upgrade && apt-get update && apt-get autoremove && apt-get autoclean"
else
  sudo sh -c "apt-get update && apt-get upgrade && apt-get dist-upgrade && apt-get update && apt-get install $@ && apt-get autoremove && apt-get autoclean"
fi

I have this script deployed in a lazy manner, I just have it sitting in my users home folder and called it “up”, I did do a “chmod +x up” and just start it like this:

Create Linux dm-crypt BTRFS RAID 1

Wed, 12 Feb 2020 08:35:36 +0000

To do this you need two empty drives, with the guide below all data on the drive will be lost if it is not empty!

1. Install cryptsetup

apt-get install cryptsetup

2. Create the dm-crypt

cryptsetup -y -v luksFormat /dev/sdb
cryptsetup -y -v luksFormat /dev/sdc

(Make sure to use the correct device. To show available devices use “lsblk”.)

3. Mount the cryptsetup disk

cryptsetup luksOpen /dev/sdb disk1
cryptsetup luksOpen /dev/sdc disk2

4. Check if this was successful

ls -l /dev/mapper/disk*

or
sudo cryptsetup -v status disk1
sudo cryptsetup -v status disk2

5. Create BTRFS volume RAID 1, this means all data and meta-data is mirrored, which means if you use 2 drives with i.e. 4TB each you can only use 4TG over all in the BTRFS mounted volume.

mkfs.btrfs -m raid1 -d raid1 /dev/mapper/disk1 /dev/mapper/disk2

You could list more than two drive, for example to increase redundancy, but if you want to use more drive to increase storage you would have to use a different Raid level.

Size of each table in a database of MySQL or MariaDB

Wed, 02 Oct 2019 19:31:42 +0000

I found something pretty useful, just a quick #MySQL / #MariaDB code snippet to show the size of each table of the currently selected database.

SELECT table_name ,
  round(((data_length + index_length) / 1024 / 1024), 2) as SIZE_MB
FROM information_schema.TABLES
WHERE table_schema = DATABASE() ORDER BY SIZE_MB DESC;

You have to start ‘mysql’ from CLI, in any terminal emulator of you choice, by adding the database name it should select when started, so lets say the database you’re looking to get the table sizes from is ‘wordpress’ you’d have to call ‘mysql wordpress’ and then in mysql you’d have to enter the whole code snippet from above and hit enter afterwards.

How to add a swap drive to your system

Wed, 02 Oct 2019 08:04:57 +0000

How to add a swap drive to your system, in this case I did this for a virtual machine (qemu) running Arch Linux.

See at the bottom for information about the virtual drive for qemu.

List current available to system disks:

sudo blkid

List all disks:

sudo lsblk

Format as swap:

sudo mkswap /dev/vdb

gives back the UUID

Now the new swap disk will be shown when executing this again:

sudo blkid

(also give the UUID)

rename

Mon, 29 Apr 2019 20:06:29 +0000

… is an easy to use and powerful tool, it can be used to replace part of file name (string1) with some other string. Something one can also do with some “sed” hack, but this tool is much easier to use, especially for beginners.

You can get all information needed from “rename –help” (here from Linux Mint):

rename --help
Usage:
    rename [ -h|-m|-V ] [ -v ] [ -n ] [ -f ] [ -e|-E perlexpr]*|perlexpr
    [ files ]

Options:
    -v, -verbose
            Verbose: print names of files successfully renamed.

    -n, -nono
            No action: print names of files to be renamed, but don't rename.

    -f, -force
            Over write: allow existing files to be over-written.

    -h, -help
            Help: print SYNOPSIS and OPTIONS.

    -m, -man
            Manual: print manual page.

    -V, -version
            Version: show version number.

    -e      Expression: code to act on files name.

            May be repeated to build up code (like "perl -e"). If no -e, the
            first argument is used as code.

    -E      Statement: code to act on files name, as -e but terminated by
            ';'.

I did use this tool rename some files that contained the string “www”, which I had to replace with “web”, lets say there were files named like this:

SSH config, ssh via jumphost and autossh (ssh to Tor hidden service)

Sun, 14 Apr 2019 20:03:29 +0000

This will be a short post about the above mentioned parts, lets start right away.

SSH config

Every user can have a SSH client configuration file, it is located in ~/.ssh/config (where config ist the filename).
My SSH config file, I guess as many other users file, grew over time. Lets start with some things from my file.

There is the Host part, it usually contains the name you want to assign to the host to use it later on. Tipp, use some short and of course unique name.

Resize qemu VM disk

Sat, 16 Mar 2019 22:48:48 +0000

VM runterfahren

Image der VM vergrössern:

sudo qemu-img resize /var/lib/libvirt/images/vm_disk.img +15GB

Je nach Setup ist sudo nicht nötig, durch den Befehl wird die Diskimagedatei um 15 GB vergrößert.

VM starten

Weiter geht es in der VM auf der Konsole.

Partitioen mit parted anzeigen lassen:

parted -l

Ausgabe so oder ähnlich:
Model: Virtio Block Device (virtblk)
Disk /dev/vda: 53,7GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Disk Flags:

Number Start End Size Type File system Flags
1 1049kB 53,7GB 53,7GB primary btrfs boot

explainshell.com

Sat, 16 Mar 2019 21:09:38 +0000

Did you know explainshell.com yet? Try it, for example with that command from last time

sudo lsof -i -P -n | grep LISTEN

this is an amazing web site I use often so see what commands do that I find somewhere. Try it.

disable vim visual mode

Sat, 16 Mar 2019 20:52:31 +0000

It drives me nuts that I cannot copy something from a ssh terminal when I use vim. I have no clue what this visual mode is meant to do besides anoying my.

My solution:

echo "set mouse-=a" >> ~/.vimrc

no more visual mode -> marking and copying text from vim by using the mouse works again.

lsof - local open ports

Thu, 14 Mar 2019 23:42:02 +0000

A short one:

Command

lsof -i -P -n | grep LISTEN

This will output all the ports the system is listing on. You might have to prepend “sudo”.

So then the command will be:

sudo lsof -i -P -n | grep LISTEN

The list is long without the “grep”, it will filter the output and only show the lines which contain “LISTEN”.

Edit:
Oliver from Hubzilla (part of the Fediverse) pointed out that

Impressum und Datenschutz

Thu, 14 Mar 2019 23:20:24 +0000

Für diese Seite gilt das Impressum und der Datenschutzhinweis auf blog.utzer.de.

Kontaktdaten sind ebenfalls unter dem obigen Link zu finden.

rsync

Thu, 14 Mar 2019 23:00:50 +0000

This is kind of my cheat sheet, nothing fancy, just what I need.

Command:

rsync -chavzP --stats 'host:~/RemotePath' ./LocalPath

rsync - Befehl
-c, –checksum
-h, –human-readable
-a, –archive
-v, –verbose
-z, –compress
-P - equivalent to –partial –progress
–stats - This tells rsync to print a verbose set of statistics on the file transfer
‘host:~/RemotePath’ - is the source path (in this case a remote path.
./LocalPath - ist the destination

Hello World

Thu, 14 Mar 2019 22:45:23 +0000

I decided to write my notes about Linux, technology, programming, scripts, tor and other things into a blog.

I do not think these are best solutions, neither to I think this are good solutions, but I hope to help some people and after all I hope to get feedback and lern something from those reading my notes.

Please comment on a post to help me to improve it.