Markus's questions

I'm using Ubuntu 20.04 64 bit on a raspberry pi 4 with a SD card as boot drive and one external hard drive.

There are a lot of tutorials about how to move the data directory of Nextcloud itself to an external drive which I followed without issue (had to grant access to removable media to the snap but that was it).

Unfortunately I can't find much info about how to change the location of the MySQL server's data directory (e.g. where ibdata1 is stored).

Changing this directory would be a great thing, since sd cards aren't well suited for all these write cycles… I can imagine that, once all my directories are synched with my server, most of the actual writing would happen to the database, not even the file storage itself.

Does anyone tried this before?

Thanks in advance Markus

A dynamically growing .img-file is mounted to my user's home directory. Its file system is btrfs and it's encrypted via LUKS.

Keyslot 0: A file created by

dd if=/dev/urandom of=<some file> bs=512 count=8

Keyslot 1: A password for manual decrition.

The keyfile is located on a thumbdrive which, when inserted, is automatically mounted at

/mnt/clavis

What I'm trying to accomplish:

• On boottime the system tries to find /mnt/clavis/home.key
• If this fails (e.g. if the thumbdrive isn't inserted): Prompt for password.

The following setups are working:

/etc/crypttab
home <path to image> none luks,discard

And (when the thumbdrive is inserted):

/etc/crypttab
home <path to image> /mnt/clavis/home.key luks,discard

However it does not work when the thumbdrive isn't inserted. It just hangs for some time and then continues to boot without mounting /home/. I can then manually luksOpen the image but invoking cryptdisks_start home fails.

What am I doing wrong? Tutorials on how to use password- and keyfile-based encryption simultaneously are hard to find.

I'm using Ubuntu 19.04.

I have a rather unusual scenario. There is a ntfs-harddrive in my computer which I would like to mount, which isn't difficult on its own.

But there is an .img-file on said harddrive which I would like to mount at /usr.

Because this is an important system directory, it needs to be mounted very early on in the boot process.

An entry in the fstab - even in the right order - doesn't seem to fix this issue.

Systemd can do mounting as far as I know. What "RequiredBy"-Targets would I need to specify?

Thanks in advance

Markus

I have a 64 GB (USB 3.0) thumb drive which I would like to seperate in three different parts.

1. A section for a bootable XUbuntu image.
2. A 10 GB section (ext4 formatted).
3. A ~50 GB section (fat32 formatted).

Usually I just type

dd if=/home/<user>/Downloads/<distro>.iso of=/dev/sdb bs=1M

in order to create a bootable thumb drive.

I then tried using fdisk to add additional partitions as described above.

I was able to boot into the live image but could not mount neither the ext4 not the fat32 partitions (error message said it was busy).

Then I tried using fdisk to create three partitions and typing:

dd if=/home/<user>/Downloads/<distro>.iso of=/dev/sdb1 bs=1M

with sdb1 beeing the first roughly 1,5 GB partition.

I was able to boot into the live image again. But only on some machines. Windows however didn't recognized the fat32 partition.

What am I doing wrong?

Thanks in regards.

Markus

I'm hosting a page and have ssh-access to the webspace.

The site allows modification by it's users. To be able to revert it back to an older state, I thought about rsync to create an incremental backup every 30 minutes using cron to launch the following script.

#!/bin/bash

# Binaries
RSYNC=`which rsync`
LN=`which ln`
MKDIR=`which mkdir`
#TODO: Is this enough to make the script distro independent?

# Other Variables
source="<username>@<provider>:<workspace path>"
target="<local backup path>"
# Date ...
year=$(date +%Y)
month=$(date +%m)
day=$(date +%d)
# ... and time
hour=$(date +%H)
minute=$(date +%M)

# Prepare directories
$MKDIR -p $target/$year/$month/$day/"$hour"_"$minute"/
# TODO: Why is this necessary? The actual backup won't work without this line
# saying "directory does not exist...".

# Actual backup
$RSYNC -av --delete "$source" "$target/$year/$month/$day/"$hour"_"$minute"/" --link-dest="$target/latest/"
$LN -nsf "$target/$year/$month/$day/"$hour"_"$minute"/" "$target/latest"

# End script
exit 0

The script seems to work so far but the target-path bloated to roughly three times the actual size of the source path within in the last three days.

Incremental backuping should only lead to a small increase, right?

What am I doing wrong?

Thanks in advance

Markus

Might be more of an xfce related problem rather than one in ubuntu. I'm not sure.

To use different theme than greybird in Xubuntu 18.04 i followed these instructions:

https://wiki.xfce.org/howto/install_new_themes

(Points "GTK+ interfaces" and "Windows decorations")

But I noticed that only the system wide installation in

/usr/share/themes
/usr/share/icons

works.

If I place themes in

~/.local/share/themes

or

~/.icons/

respectively, the themes seem to be recocgnized only partially. Some parts of the windows like the close button and some bars appear in the new theme (which is selectable in various customization tools) but most of the windows content (buttons etc.) appear in some Windows-98-like form.

What am I doing wrong?

It isn't that much of a pressing matter since at least the installation in

/usr

works. But installing it in my home directory seems like the cleaner solution.

Thanks in regards

Markus

I recently switched to Ubuntu 17.10 from Ubuntu 16.04.

So far, I used xmodmap to remove Caps_Lock and replace it with the backslash-symbol.

This doesn't seem to work under 17.10 (maybe because xmodmap is an X11 app and 17.10 uses Wayland?). Is there another way to get this done?

I'm having a problem with the BCM43142A0 Bluetooth module. I've already tried this solution: Bluetooth Broadcom 43142 isn't working.

BT hardware such as headphones can now be connected but keep losing connection (audio stops and resumes out of joint with video). Als othe system keeps freezing. Last entries /var/log/syslog are bluetooth-related almost every time.

I have a usb-dongle which should be working but need to disable the internal one (hoping that this will end the crashing).

lsusb gives:

Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 001 Device 005: ID 048d:8386 Integrated Technology Express, Inc. 
Bus 001 Device 003: ID 03eb:8c1d Atmel Corp. 
Bus 001 Device 006: ID 105b:e065 Foxconn International, Inc. BCM43142A0 Bluetooth module
Bus 001 Device 004: ID 5986:0535 Acer, Inc  
Bus 001 Device 007: ID 0a12:0001 Cambridge Silicon Radio, Ltd Bluetooth Dongle (HCI mode)
Bus 001 Device 002: ID 05e3:0608 Genesys Logic, Inc. Hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

I would like to disable the one from foxconn while leaving the other one (from cambridge silicon radio) active.

I think this isn't possible by editing /etc/modprope.d/blacklist because this would deactivate bluetooth altogether.

I accidentally executed

sudo shred -v -n 0 -z /dev/sdb

to prepare a thumb drive for formatting. But /dev/sdb was my external hdd. Although I immediately became aware of my mistake and pressed ctrl+c

lsblk

shows that the ext4 partition on the external hdd got lost. I think shred copied some zeros into the space where the partition table was.

Is there any hope, that I can get my data back? I already tried the data rescue option in gparted but the programm hangs on different devices when attempting this.

I have a string like this

<user>@<server>:<port>:/foo/bar

and I would like to extract the user, server, port and directory.

The user can easily be extracted by

echo <string> | awk -F"@" '{print $1;}'

But the server lies within two different delimeters. Is this possible via awk?

I'm working on a script that downloads large files like installers, youtube video series or torrents. It's supposed to work on a Raspbian. So the main part has to be delt with in a screen session. Or else the user would have to keep the ssh connection active all the time.

It's also supposed to get it's input from a textfile containing multiple entries like:

http://youtube.com/BlaBla video ~/Videos
http://vlc-project.org/downloads/BlaBla file ~/Downloads
BlaBla.torrent torrent ~/Downloads

So the codeblock would be something like:

while read -r line; do
  # Code for simple file
  # Code for Video
  # Code for torrent
done < "$inputFile"

How do I execute the entire while loop in a screen session? Is this even possible?

Greetings and thanks in advance

Markus

I'm using a Raspberry Pi with two ethernet ports as a router. The network looks like this.

"Internet" <--(…)--> Fritz!Box <--(172.16.x.y)--> [eth1, dhcp] Raspberry Pi [eth0, static] <--(192.168.178.z)--> "Switches, PCs, etc."

The Raspberry Pi is running raspbian. It can connect to the internet, update, install software, etc..

rc.local looks like this

#!/bin/sh -e
#
# rc.local
#
# This script is executed at the end of each multiuser runlevel.
# Make sure that the script will "exit 0" on success or any other
# value on error.
#
# In order to enable or disable this script just change the execution
# bits.
#
# By default this script does nothing.
# Print the IP address
_IP=$(hostname -I) || true
if [ "$_IP" ]; then
  printf "My IP address is %s\n" "$_IP"
fi
#
# iptables-Regeln zum Routing von eth0 auf eth1
lan_if=eth0
wan_if=eth1
# Loopback-Traffic sollte aktiv sein.
iptables -A INPUT -i lo -j ACCEPT
# Traffic von LAN-Seite aus aktzeptieren
iptables -A INPUT -i $lan_if -j ACCEPT
###################################
# ROUTING #########################
###################################
# eth1 ist das WAN
# eth0 ist das LAN
# Aufgebaute Verbindungen zulassen
iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
# Was ist "Masquerade"
iptables -t nat -A POSTROUTING -o $wan_if -j MASQUERADE
# Weiterleitung
iptables -A FORWARD -i $wan_if -o $lan_if -m state --state RELATED,ESTABLISHED -j ACCEPT
# Ausgehende Verbindungen von der LAN-Seite zulassen
iptables -A FORWARD -i $lan_if -o $wan_if -j ACCEPT
#
exit 0

dnsmasq.conf:

interface=eth0
dhcp-range=192.168.178.2,192.168.178.254,12h
dhcp-host=28.D2.44.5B.99.A9,permutare,192.168.178.55,12h
dhcp-option=3,192.168.178.1

interfaces:

# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

# The loopback network interface
auto lo
iface lo inet loopback

# WAN
auto eth1
  iface eth1 inet dhcp
#  address 172.16.0.2
#  netmask 255.255.0.0
#  gateway 172.16.0.1
#  dns-nameservers 172.16.0.1

# LAN
auto eth0
  iface eth0 inet static
  address 192.168.178.1

"resolvconf" ist installed.

Computers in the "192.168.178.z"-network cannot access the internet or computers in the "172.16.x.y" network. They can resolve the IP-adresses of websites they never pinged before, though. What am I doing wrong?

Thanks in advance,

Markus

I'm using my Ubuntu-Server and transmission-cli to download torrents overnight. When I try to download the Ubuntu 12.04.5 Server torrent transmission connects to various peers, but doesn't download anything.

The given command is:

/usr/bin/screen -a -S rdownload_$torrent_name /usr/bin/transmission-cli -w "$target_directory" $remote_home/$torrent_name

This is the (screened) output:

transmission-cli 2.52 (13304)
[00:04:21.914] Transmission 2.52 (13304) started
[00:04:21.917] RPC Server: Adding address to whitelist: 127.0.0.1
[00:04:21.961] UDP: Failed to set receive buffer: requested 4194304, got 327680
[00:04:21.961] UDP: Please add the line "net.core.rmem_max = 4194304" to /etc/sysctl.conf
[00:04:21.961] UDP: Failed to set send buffer: requested 1048576, got 327680
[00:04:21.961] UDP: Please add the line "net.core.wmem_max = 1048576" to /etc/sysctl.conf
[00:04:21.961] DHT: Reusing old id
[00:04:21.965] DHT: Bootstrapping from 89 IPv4 nodes
[00:04:22.029] Saved "/home/pi/.config/transmission/torrents/ubuntu-12.04.5-server-amd64.iso.859da4d7affd6efd.torrent"
[00:04:22.249] Port Forwarding (NAT-PMP): initnatpmp succeeded (0)
[00:04:22.251] Port Forwarding (NAT-PMP): sendpublicaddressrequest succeeded (2)
[00:04:22.274] Port Forwarding (UPnP): Found Internet Gateway Device "http://192.168.178.1:49000/igdupnp/control/WANIPConn1"
[00:04:22.275] Port Forwarding (UPnP): Local Address is "192.168.178.33"
[00:04:22.295] Port Forwarding (UPnP): Port forwarding through "http://192.168.178.1:49000/igdupnp/control/WANIPConn1", service "urn:schemas-upnp-org:service:WANIPConnection:1". (local address: 192.168.178.33:51413)
[00:04:22.297] Port Forwarding: State changed from "Not forwarded" to "Starting"
Progress: 0.0%, dl from 0 of 0 peers (0 kB/s), ul to 0 (0 kB/s) [None]          [00:04:22.979] ubuntu-12.04.5-server-amd64.iso: Could not connect to tracker
[00:04:22.981] ubuntu-12.04.5-server-amd64.iso: Retrying announce in 303 seconds.
Progress: 0.0%, dl from 0 of 36 peers (0 kB/s), ul to 0 (0 kB/s) [None]
Progress: 0.0%, dl from 0 of 61 peers (0 kB/s), ul to 0 (0 kB/s) [None]         [00:04:30.027] Port Forwarding: State changed from "Starting" to "???"
Progress: 0.0%, dl from 0 of 61 peers (0 kB/s), ul to 0 (0 kB/s) [None]         [00:04:33.001] ubuntu-12.04.5-server-amd64.iso: Starting IPv4 DHT announce (poor, 16 nodes)
Progress: 0.0%, dl from 0 of 60 peers (0 kB/s), ul to 0 (0 kB/s) [None]         [00:04:51.198] ubuntu-12.04.5-server-amd64.iso: Scrape error: Could not connect to tracker
[00:04:51.198] ubuntu-12.04.5-server-amd64.iso: Retrying scrape in 910 seconds.
Progress: 0.0%, dl from 0 of 60 peers (0 kB/s), ul to 0 (0 kB/s) [None]         [00:08:13.782] ubuntu-12.04.5-server-amd64.iso: IPv4 DHT announce done
Progress: 0.0%, dl from 0 of 60 peers (0 kB/s), ul to 0 (0 kB/s) [None]         [00:09:25.536] ubuntu-12.04.5-server-amd64.iso: Could not connect to tracker
[00:09:25.537] ubuntu-12.04.5-server-amd64.iso: Retrying announce in 1815 seconds.
Progress: 0.0%, dl from 0 of 48 peers (0 kB/s), ul to 0 (0 kB/s) [None]   [00:10:30.114] Saved "/home/pi/.config/transmission/resume/ubuntu-12.04.5-server-amd64.iso.859da4d7affd6efd.resume"
Progress: 0.0%, dl from 0 of 53 peers (0 kB/s), ul to 0 (0 kB/s) [None]     

In the download destination no directories are building up. The strange thing is, that another torrent from earlier today worked fine. But I didn't launched it via screen, though. Any ideas about possible reasons?

Thanks in regard, Markus

When I do something like:

rsync Videos/YouTube/LetsPlays foo@bar:/home/foo/

The resulting directory structure looks like:

/home/foo/LetsPlays

I've read the man pages but couldn't an option to maintain the directory structure, aiming for

/home/foo/Videos/YouTube/LetsPlays

as result. Any ideas?

As always thanks in regards, Markus

To boil it down: The following command in bash

echo $(ssh -t pi@doctor "sudo stat -c \"%U\" /var/www/candy/example/index.html")101

Gives the this result

Connection to doctor closed.
101-data

While

echo $(ssh -t pi@doctor "sudo stat -c \"%U\" /var/www/candy/example/index.html")

gives

Connection to doctor closed.
www-data

Why is this?

Background: I'm using this script (called ced.sh):

for ARG; do
        name=${ARG##*/}
        echo name=$name
        path=${ARG%/*} 
        echo path=$path
        owner=$(echo $(ssh -t $remote_user@$server "sudo stat -c \"%U\" $ARG"))
        echo owner=$owner
        group=$(echo $(ssh -t $remote_user@$server "sudo stat -c \"%G\" $ARG"))
        echo group=$group
        perms=$(echo $(ssh -t $remote_user@$server "sudo stat -c \"%a\" $ARG"))
        echo perms=$perms
        read -p "Gibt es einen Dienst/Server, der auf diese Datei zurückgreift (notfalls leer lassen)? " service
        echo service=$service
        echo "name="\"$name\" "path="\"$path/\" "owner="\"$owner\" "group="\"$group\" "perms="$perms "service="$service
done

Its purpose is to read some information (e.g. owner, group, permissions) from files on a server, which I'd like to edit locally. The last line should produce an output that can be stored in a file.

It would have been rewritten to:

echo "name="\"$name\" "path="\"$path/\" "owner="\"$owner\" "group="\"$group\" "perms="$perms "service="$service >> "$HOME/...bla bla..."

The output looks like this:

Software/EigeneProgramme/ced.sh -p /var/www/candy/example/index.html
name=index.html
path=/var/www/candy/example
Connection to doctor closed.
owner=www-data
Connection to doctor closed.
group=www-data
Connection to doctor closed.
perms=644
Gibt es einen Dienst/Server, der auf diese Datei zurückgreift (notfalls leer lassen)? apache
service=apache
 service=apacheta path="/var/www/candy/example/" owner="www-data

I don't understand why echo produces the last line. It seems that it is writing to line in on. Did I forget to escape something?

Here's the problem: Everytime I close gedit all of my own (LaTeX)snippets are lost when I launch it for the next time. Default snippets are still available and working.

What I tried so far:

• Restart my computer (I know, this is crude, but sometimes it helps.)
• Re-install gedit-plugins (apt-get purge for removal, even cruder.)
• Export my own snippets within the "manage snippets menu" and import them. The reimport didn't work. I can point the tar.gz an click on "open" but nothing happens.

I'm using Ubuntu 14.04 LTS on a Core i5.

Thanks in advance, Markus

I'm working on a script to wake different LCs on my LAN. MAC-Adresses are hard to memorize so I made myself a list that contains information about the respective PCs. Right now the list looks like:

dragoner xxx.xxx.xxx.xxx xx:xx:xx:xx:xx:xx
theseus yyy.yyy.yyy.yyy yy:yy:yy:yy:yy:yy
...

That means, that new entries will always have to be in the form: netbios-name ipv4 mac. The advantage is, that such a list can easily be queried by grep and awk.

I'd rather like to have a list like that:

netbios=dragoner ip4=xxx.xxx.xxx.xxx mac=xx:xx:xx:xx:xx:xx
netbios=theseus mac=yy:yy:yy:yy:yy:yy ip4=yyy.yyy.yyy.yyy
...

In that manner new information could be added more easily and row wouldn't have to have a certain number of columns... but I'm failing to query it via awk.

On my Mac I was using LaTeXit. It takes a LaTeX code and produces instant pdfs (or pngs, jpgs, etc…).

I'm sure there's a similar programme for Ubuntu. But I was unable to find one.

Any ideas?

Thanks in advance, Markus.

I have a complete date plus hours and minutes. I would like to add a number of seconds and display the result as a date "day.month.year hour:minute".

"date" doesn't seem to be able to add seconds to a given date.

As far as I know, bash variables do not have a certain type.

My problem is, I need to convert a time stamp (always in format: hh:mm:ss) to a single integer representing seconds.

So I cut the hh, mm and ss parts into separate strings and use expr to calculate the seconds integer like:

TIME=expr $HH \* 3600 + $MM \* 60 + $SS

But when e.g. $HH=00 then expr won't work. Is it possible to convert strings like 00 or 01 to integers?