velis's questions

Some packages, like Intellij's PyCharm, etc. take an insanely long time to start for the first time. I found this question which is about the same problem, but asked wrongly, it seems.

Basically, what I would like is snap to perform the "first start" of the snap app for me in the background as the OS boots / I log in so that I wouldn't have to wait literally minutes for the app to start.

Or is there a setting that would utilise all of my processor's cores as it decompresses the package? As I understand this, it's possibly a problem with the default xz compression for the packages, though it seems unlikely as - as the mentioned issue explains - it wasn't a problem before 2021.x versions. Regardless, subsequent starts are fast, so I want the "first one" done for me in the background.

So I have a JSON file which I grep for certain variables:

cat myfile | grep -E "group_(var1|var2|var3)"

The output comes out like this:

"group_var1": "value1"
"group_var2": "value2"
"group_var3": "value3"

I'd like to interpret this in my bash script such that I would end up with the three variables themselves so that I could manipulate them further.

e.g.

echo "$group_var1  $group_var2   $group_var3"

So far I've tried with read -a, awk '{ print $1 $2 }', but none of that brought me closer to my desired result.

The furthest I got was removing the quotes with the following code, but after that, I'm stuck:

params=`cat myfile | grep -E "group_(var1|var2|var3)"`
params=${params//\"}

echoing params now nets me this:

group_var1:value1,group_var2:value2,group_var3:value3,

But now I'm stuck...

Edit & solution:

I went digging further and I got it working by crudely invoking awk for each variable I wanted.

group_var1=`awk '$1=="group_var1:" { sub(",", "", $2); print $2 }' <<< $params

So I have a number of VMs running under quemu on Ubuntu 18.04. Everything works fine except accessing the VMs remotely: the slower the connection, the worse it gets. Running them on 4K monitor. Using remmina or virt-viewer, makes no difference.

• on local machine, everything is next to perfect, the only noticeable quality degradation is video full-screen.
• 1gbit LAN: noticeable delays rendering stuff, video becomes grainy even when in a small window
• 100 mbit LAN / internet: a full screen refresh can take a couple of seconds
• 20/4 mbit internet: when a full screen refresh is needed, I can observe the 64x64 squares being rendered across the screen and it takes multiple seconds. Scrolling an editor window is an operation that takes patience. Connection useless but for the most urgent tasks where patience is not an issue. Even X over ssh seems the better option here.

I compare this to Win10 RDP, which - over the same 20/4 connection - behaves as if I were at the machine in question, even for full-screen video.

The VMs are all setup thus:

• Display spice: Spice server with everything on default, no OpenGL
• Video VirtIO: model VirtIO, 3D acceleration: yes, heads:2, RAM 128MB

I tried video: QXL, but that one completely hogged my LAN, even at gbit, delivering little for the bandwidth taken (it was less performant than VirtIO).

So I've been searching for a solution to this problem finding little of import. But I did stumble on some commits into the spice master (quite a while ago). As far as I could see, the patch was merged, so this should be available, but video support is currently clearly still MJPEG for me.

So how can I enable this gstreamer support giving me a more advanced codec, like VP8 or even H264? Or am I doing something wrong and that's what's giving me pain?

I have a kubuntu host running 19.04 and remmina installed from remmina-next. Guest is regular ubuntu 19.04, accessed through spice protocol.

More than half of clipboard copies get "eaten" by the host: when copying to the clipboard, the guest will not have copied the item. Instead I will find it in the host's clipboard - not pastable on the client of course.

More details:

• copying / cutting to clipboard usually doesn't work in first try
• The client's clipboard will "know" something's wrong when a cut / copy doesn't work: it will not paste a previously successful item. See below for an example of extra weird behaviour
• second try almost always works
• since I don't know whether copying worked, I will notice this when it fails to paste
• then I go copying / pasting again - with a > 80% chance for success
• Sometimes, on the second copy, the now finally copied item will immediately paste where I previously unsuccessfully attempted to paste it. This one is especially weird - just like there was a placeholder in the editor waiting for something to get to the clipboard. Depending on the editor, it might just paste immediately after the item being copied (so I end up with a duplicate in the editor)
• I'm using CopyQ for clipboard manager in the guest, but nothing changes if I remove it and use built-in clipboard

I have noticed this with linux guests only, but not on Windows guests. I also tried virt-viewer, but it suffers from the same issue. Same when accessing the guest through RDP.

I have found some old topics about a Remmina clipboard bug, but nothing recent.

How can I diagnose and fix this issue?

Edit: I have changed the Video QXL setting from VirtIO to QXL and the problem has heavily subsided. It's not gone, but the issue now occurs in about one out of ten copies to clipboard.

I just made a fresh install of Ubuntu 19.04 into a VM. Installed xrdp via apt. Left everything on default: I believe this is how my 18.04 worked perfectly.

However, trying to connect to this VM via Remmina or Windows RDP client fails. Remmina shows a bit more because it attempts reconnection and so the result looks like this:

The login screen appears, login dialog shows but then immediately the connection is dropped.

This loops indefinitely with Remmina, but doesn't even show with Windows RDP client.

Tried the same with kubuntu 19.04 but result remains the same.

Edit: Installing remmina from their next ppa fixes this issue and I can now connect to the host xrdp server:

sudo apt-add-repository ppa:remmina-ppa-team/remmina-next
sudo apt update
sudo apt upgrade    <-- I had remmina installed from standard ubuntu repos

This is the only relevant change I did in the last few days. Will test how windows client works too, but if it does, something must have changed on the host as well...

Just spent hours diagnosing why my 18.04 VM wouldn't connect network after moving from VirtualBox to qemu.

Turns out that because of "hardware change", NIC got renamed from enp0s4 to enp1s0. And - naturally - /etc/netplan/01-netcfg.yaml specified explicitly that enp0s4 should get DHCP configuration, but not (anything else).

Comparing this to a freshly installed - and working - 19.04 didn't really help as 19.04 uses something else to configure the network. eh...

Anyway - Why is this? I have noticed such a change before, for example when I was upgrading BIOS on my motherboard. But every time this happens, I spend a lot of time diagnosing such an issue. Especially because it happens so rarely...

So, what causes this rename and how would I go about configuring my Ubuntu VMs such that this would no longer be an issue?

I've been reading (old) guides all day and I still know nothing about multiseat on Ubuntu 18.04. To make matters worse, I only have one graphics card with multiple outputs.

The only thing that gives me hope is loginctl list-seats which indicates that my Ubuntu knows about seats.

How can I set up my machine in multiseat?

Edit: output of loginctl commands.

Please note that not everything is connected. I want to first figure out how to get about it, not just plunge in. I figure each seat will have its own USB hub (HID devices + whatever else needed) + one of the displays.

loginctl list-seats
SEAT            
seat0           

1 seats listed.

loginctl seat-status seat0

seat0
Sessions: *c1
 Devices:
      ├─/sys/devices/LNXSYSTM:00/LNXPWRBN:00/input/input1
      │ input:input1 "Power Button"
      ├─/sys/devices/LNXSYSTM:00/LNXSYBUS:00/PNP0C0C:00/input/input0
      │ input:input0 "Power Button"
      ├─/sys/devices/pci0000:00/0000:00:01.3/0000:03:00.0/usb1
      │ usb:usb1
      │ ├─/sys/devices/pci0000:00/0000:00:01.3/0000:03:00.0/usb1/1-12/1-12:1.0/input/input11
      │ │ input:input11 "iMON USB Touchscreen (15c2:0034)"
      │ ├─/sys/devices/pci0000:00/0000:00:01.3/0000:03:00.0/usb1/1-12/1-12:1.0/input/input2
      │ │ input:input2 "iMON Panel, Knob and Mouse(15c2:0034)"
      │ └─/sys/devices/pci0000:00/0000:00:01.3/0000:03:00.0/usb1/1-12/1-12:1.0/rc/rc0/input3
      │   input:input3 "iMON Remote (15c2:0034)"
      ├─/sys/devices/pci0000:00/0000:00:01.3/0000:03:00.0/usb2
      │ usb:usb2
      ├─/sys/devices/pci0000:00/0000:00:03.1/0000:26:00.0/drm/card0
      │ [MASTER] drm:card0
      │ ├─/sys/devices/pci0000:00/0000:00:03.1/0000:26:00.0/drm/card0/card0-DP-1
      │ │ [MASTER] drm:card0-DP-1
      │ ├─/sys/devices/pci0000:00/0000:00:03.1/0000:26:00.0/drm/card0/card0-DP-2
      │ │ [MASTER] drm:card0-DP-2
      │ ├─/sys/devices/pci0000:00/0000:00:03.1/0000:26:00.0/drm/card0/card0-DP-3
      │ │ [MASTER] drm:card0-DP-3
      │ ├─/sys/devices/pci0000:00/0000:00:03.1/0000:26:00.0/drm/card0/card0-DVI-D-1
      │ │ [MASTER] drm:card0-DVI-D-1
      │ └─/sys/devices/pci0000:00/0000:00:03.1/0000:26:00.0/drm/card0/card0-HDMI-A-1
      │   [MASTER] drm:card0-HDMI-A-1
      ├─/sys/devices/pci0000:00/0000:00:03.1/0000:26:00.0/drm/renderD128
      │ drm:renderD128
      ├─/sys/devices/pci0000:00/0000:00:03.1/0000:26:00.1/sound/card0
      │ sound:card0 "NVidia"
      │ ├─/sys/devices/pci0000:00/0000:00:03.1/0000:26:00.1/sound/card0/input12
      │ │ input:input12 "HDA NVidia HDMI/DP,pcm=3"
      │ ├─/sys/devices/pci0000:00/0000:00:03.1/0000:26:00.1/sound/card0/input13
      │ │ input:input13 "HDA NVidia HDMI/DP,pcm=7"
      │ ├─/sys/devices/pci0000:00/0000:00:03.1/0000:26:00.1/sound/card0/input14
      │ │ input:input14 "HDA NVidia HDMI/DP,pcm=8"
      │ └─/sys/devices/pci0000:00/0000:00:03.1/0000:26:00.1/sound/card0/input15
      │   input:input15 "HDA NVidia HDMI/DP,pcm=9"
      ├─/sys/devices/pci0000:00/0000:00:07.1/0000:27:00.3/usb3
      │ usb:usb3
      ├─/sys/devices/pci0000:00/0000:00:07.1/0000:27:00.3/usb4
      │ usb:usb4
      ├─/sys/devices/pci0000:00/0000:00:08.1/0000:28:00.3/sound/card1
      │ sound:card1 "Generic"
      │ ├─/sys/devices/pci0000:00/0000:00:08.1/0000:28:00.3/sound/card1/input10
      │ │ input:input10 "HD-Audio Generic Front Headphone"
      │ ├─/sys/devices/pci0000:00/0000:00:08.1/0000:28:00.3/sound/card1/input4
      │ │ input:input4 "HD-Audio Generic Front Mic"
      │ ├─/sys/devices/pci0000:00/0000:00:08.1/0000:28:00.3/sound/card1/input5
      │ │ input:input5 "HD-Audio Generic Rear Mic"
      │ ├─/sys/devices/pci0000:00/0000:00:08.1/0000:28:00.3/sound/card1/input6
      │ │ input:input6 "HD-Audio Generic Line"
      │ ├─/sys/devices/pci0000:00/0000:00:08.1/0000:28:00.3/sound/card1/input7
      │ │ input:input7 "HD-Audio Generic Line Out Front"
      │ ├─/sys/devices/pci0000:00/0000:00:08.1/0000:28:00.3/sound/card1/input8
      │ │ input:input8 "HD-Audio Generic Line Out Surround"
      │ └─/sys/devices/pci0000:00/0000:00:08.1/0000:28:00.3/sound/card1/input9
      │   input:input9 "HD-Audio Generic Line Out CLFE"
      └─/sys/devices/virtual/misc/rfkill
        misc:rfkill

Starting with 18.04 on both ends I want to access my remote machine via RDP.

I have verified that the client using remmina works very fast using GFX RFX colour depth connecting to a Windows 10 RDP server. Please note that neither of GFX AVC variants works as there seems that libfreerdp doesn't come prebuilt with their support on 18.04 (remmina installed by apt, not manually from their repo).

When I connect to an Ubuntu 18.04 server running xrdp, performance is not nearly the same: the entire experience is laggy, especially at resolutions above full HD. It is clearly not using the advanced codecs.

I tried installing Remmina from their repo to test the AVC depths, but the only thing that changes is removing the AVC depths from the list altogether so now I can't even select them (previously they just didn't work). Apt didn't touch the libfreerdp libraries though when I upgraded Remmina from their repo.

How can I set up my systems such that I will have good performance?

I'm using this command to establish NAT on my VM container:

iptables -t nat -A PREROUTING -d ${MAIN_IP} -p tcp --dport ${2} -j DNAT --to-destination ${SUBNET}${3}

with

• MAIN_IP being main server's global IP
• SUBNET being first three numbers of my VM subnet, e.g. "192.168.1."
• $2 being port I want to forward
• $3 being the last subnet segment, e.g. 20

This works fine for straight NATing.

But today I wanted to declare a DNAT to SSH port, so I set $2 to 5022 and $3 to 20:22, resulting in the following line, for clarity:

iptables -t nat -A PREROUTING -d ${MAIN_IP} -p tcp --dport 5022 -j DNAT --to-destination 192.168.1.20:22

Yet this one does not work: connections time out when I try to ssh to the VM. Note that they do not time out when I don't use nat, so ssh [email protected] works just fine. It only doesn't work through NAT.

UFW is not enabled on container server. It listens to pretty much nothing so there's no need to close anything - or so I hope.

I'm assuming the DNAT rule is correct, so how do I determine what's blocking me?

Edit: output of nat table:

#iptables -t nat -L
Chain PREROUTING (policy ACCEPT)
target     prot opt source               destination
DNAT       tcp  --  anywhere             my-server         tcp dpt:2113 to:192.168.1.35
DNAT       tcp  --  anywhere             my-server         tcp dpt:2115 to:192.168.1.35

Chain INPUT (policy ACCEPT)
target     prot opt source               destination

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination

Chain POSTROUTING (policy ACCEPT)
target     prot opt source               destination
MASQUERADE  all  --  anywhere             anywhere

Edit 2: I'm temporarily solving the issue with having VM sshd listen to multiple ports. This way NAT works just fine.

I want ufw to block everything on my external interface (enp6s0) but allow everything on my internal ones (br0, tap0).

I had huge issues with this (ufw was blocking stuff on br0 even though I set up a rule to allow in on enevrything), so I set ufw to by default allow everything and then started adding exceptions for the interface I want blocked, like so:

ufw deny in on enp6s0 to any port 67 proto udp

I have a few of these for every port I don't want accessed from outside. But this solution makes me uneasy: basically I'm leaving everything open, just not listening on it. Sooner or later I'm going to forget to protect something.

So I went the other way around and wanted to create a set of rules which would allow certain ports but deny everything else, like so:

ufw insert 1 allow in on enp6s0 from any port ssh proto tcp
ufw insert 2 allow in on enp6s0 from any port http proto tcp
ufw insert 3 deny in on enp6s0 from any port 30:65535 proto tcp

The last command was intentionally leaving port 22 open so I could test effectiveness of the rules without risking losing my ssh connection to the server.

However, adding the deny rule immediately blocked the entire server. Everything, not just 30:65535. nmap thought it was down. Just by some huge luck, my existing ssh session remained active so I could delete the rule.

Now, I know I'm not some ufw guru or something, but this really came as (another) shock to me: it seems I have no idea about how it works.

Can anyone enlighten me on the deny rule? How I need to set it up?

Final edit: It turned out that uninstalling & reinstalling ufw fixed the issues. It seems I messed up some setting at some point which caused all the unexplained behaviour.

Edit: my network config

# interfaces(5) file used by ifup(8) and ifdown(8)
auto lo
iface lo inet loopback

# Our additions start here:
# tap interface (VMs will use this one)
auto tap0
iface tap0 inet manual
    pre-up ip tuntap add tap0 mode tap user root
    up ip link set dev tap0 up
    post-down ip link del dev tap0

# bridge
auto br0
iface br0 inet static
    bridge_ports tap0
    address 192.168.100.1
    netmask 255.255.255.0
    broadcast 192.168.100.255

iptables -S

-P INPUT ACCEPT
-P FORWARD ACCEPT
-P OUTPUT ACCEPT
-N ufw-after-forward
-N ufw-after-input
-N ufw-after-logging-forward
-N ufw-after-logging-input
-N ufw-after-logging-output
-N ufw-after-output
-N ufw-before-forward
-N ufw-before-input
-N ufw-before-logging-forward
-N ufw-before-logging-input
-N ufw-before-logging-output
-N ufw-before-output
-N ufw-logging-allow
-N ufw-logging-deny
-N ufw-not-local
-N ufw-reject-forward
-N ufw-reject-input
-N ufw-reject-output
-N ufw-skip-to-policy-forward
-N ufw-skip-to-policy-input
-N ufw-skip-to-policy-output
-N ufw-track-forward
-N ufw-track-input
-N ufw-track-output
-N ufw-user-forward
-N ufw-user-input
-N ufw-user-limit
-N ufw-user-limit-accept
-N ufw-user-logging-forward
-N ufw-user-logging-input
-N ufw-user-logging-output
-N ufw-user-output
-A INPUT -j ufw-before-logging-input
-A INPUT -j ufw-before-input
-A INPUT -j ufw-after-input
-A INPUT -j ufw-after-logging-input
-A INPUT -j ufw-reject-input
-A INPUT -j ufw-track-input
-A FORWARD -j ufw-before-logging-forward
-A FORWARD -j ufw-before-forward
-A FORWARD -j ufw-after-forward
-A FORWARD -j ufw-after-logging-forward
-A FORWARD -j ufw-reject-forward
-A FORWARD -j ufw-track-forward
-A FORWARD -i br0 -o enp6s0 -m state --state RELATED,ESTABLISHED -j ACCEPT
-A FORWARD -i enp6s0 -o br0 -j ACCEPT
-A OUTPUT -j ufw-before-logging-output
-A OUTPUT -j ufw-before-output
-A OUTPUT -j ufw-after-output
-A OUTPUT -j ufw-after-logging-output
-A OUTPUT -j ufw-reject-output
-A OUTPUT -j ufw-track-output
-A ufw-after-input -p udp -m udp --dport 137 -j ufw-skip-to-policy-input
-A ufw-after-input -p udp -m udp --dport 138 -j ufw-skip-to-policy-input
-A ufw-after-input -p tcp -m tcp --dport 139 -j ufw-skip-to-policy-input
-A ufw-after-input -p tcp -m tcp --dport 445 -j ufw-skip-to-policy-input
-A ufw-after-input -p udp -m udp --dport 67 -j ufw-skip-to-policy-input
-A ufw-after-input -p udp -m udp --dport 68 -j ufw-skip-to-policy-input
-A ufw-after-input -m addrtype --dst-type BROADCAST -j ufw-skip-to-policy-input
-A ufw-before-forward -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
-A ufw-before-forward -p icmp -m icmp --icmp-type 3 -j ACCEPT
-A ufw-before-forward -p icmp -m icmp --icmp-type 4 -j ACCEPT
-A ufw-before-forward -p icmp -m icmp --icmp-type 11 -j ACCEPT
-A ufw-before-forward -p icmp -m icmp --icmp-type 12 -j ACCEPT
-A ufw-before-forward -p icmp -m icmp --icmp-type 8 -j ACCEPT
-A ufw-before-forward -j ufw-user-forward
-A ufw-before-input -i lo -j ACCEPT
-A ufw-before-input -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
-A ufw-before-input -m conntrack --ctstate INVALID -j ufw-logging-deny
-A ufw-before-input -m conntrack --ctstate INVALID -j DROP
-A ufw-before-input -p icmp -m icmp --icmp-type 3 -j ACCEPT
-A ufw-before-input -p icmp -m icmp --icmp-type 4 -j ACCEPT
-A ufw-before-input -p icmp -m icmp --icmp-type 11 -j ACCEPT
-A ufw-before-input -p icmp -m icmp --icmp-type 12 -j ACCEPT
-A ufw-before-input -p icmp -m icmp --icmp-type 8 -j ACCEPT
-A ufw-before-input -p udp -m udp --sport 67 --dport 68 -j ACCEPT
-A ufw-before-input -j ufw-not-local
-A ufw-before-input -d 224.0.0.251/32 -p udp -m udp --dport 5353 -j ACCEPT
-A ufw-before-input -d 239.255.255.250/32 -p udp -m udp --dport 1900 -j ACCEPT
-A ufw-before-input -j ufw-user-input
-A ufw-before-output -o lo -j ACCEPT
-A ufw-before-output -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
-A ufw-before-output -j ufw-user-output
-A ufw-logging-allow -m limit --limit 3/min --limit-burst 10 -j LOG --log-prefix "[UFW ALLOW] "
-A ufw-logging-deny -m conntrack --ctstate INVALID -m limit --limit 3/min --limit-burst 10 -j RETURN
-A ufw-logging-deny -m limit --limit 3/min --limit-burst 10 -j LOG --log-prefix "[UFW BLOCK] "
-A ufw-not-local -m addrtype --dst-type LOCAL -j RETURN
-A ufw-not-local -m addrtype --dst-type MULTICAST -j RETURN
-A ufw-not-local -m addrtype --dst-type BROADCAST -j RETURN
-A ufw-not-local -m limit --limit 3/min --limit-burst 10 -j ufw-logging-deny
-A ufw-not-local -j DROP
-A ufw-skip-to-policy-forward -j ACCEPT
-A ufw-skip-to-policy-input -j ACCEPT
-A ufw-skip-to-policy-output -j ACCEPT
-A ufw-track-forward -p tcp -m conntrack --ctstate NEW -j ACCEPT
-A ufw-track-forward -p udp -m conntrack --ctstate NEW -j ACCEPT
-A ufw-track-input -p tcp -m conntrack --ctstate NEW -j ACCEPT
-A ufw-track-input -p udp -m conntrack --ctstate NEW -j ACCEPT
-A ufw-track-output -p tcp -m conntrack --ctstate NEW -j ACCEPT
-A ufw-track-output -p udp -m conntrack --ctstate NEW -j ACCEPT
-A ufw-user-input -i enp6s0 -p tcp -m tcp --sport 22 -j ACCEPT
-A ufw-user-input -i enp6s0 -p tcp -m tcp --sport 80 -j ACCEPT
-A ufw-user-input -i enp6s0 -p tcp -m tcp --sport 443 -j ACCEPT
-A ufw-user-input -i enp6s0 -p tcp -m multiport --dports 2000:2100 -j DROP
-A ufw-user-input -i enp6s0 -p tcp -m tcp --dport 53 -j DROP
-A ufw-user-input -i enp6s0 -p udp -m udp --dport 53 -j DROP
-A ufw-user-input -i enp6s0 -p udp -m udp --dport 67 -j DROP
-A ufw-user-limit -m limit --limit 3/min -j LOG --log-prefix "[UFW LIMIT BLOCK] "
-A ufw-user-limit -j REJECT --reject-with icmp-port-unreachable
-A ufw-user-limit-accept -j ACCEPT

This is a reverse question to tons of questions about how to identify which physical drive matches /dev/sdx. I want to avoid having to ask that question when a drive fails.

I have bought an adapter capable of serving 8 drives (9211-8i). Both SFF-8087 cables are nicely marked so that I know which physical drive is which.

However, the attached drives are mapped as /dev/sdx

Just for reference, my M.2 boot drive nicely mounts as /dev/nvmxxx which nicely distinguishes it from the other drives in the system.

So, how can I instruct ubuntu device mapper to map my controller attached drives as something distinct & EXACTLY matching the physical port a drive is attached to, e.g. /dev/scsi[abcdefgh]? In fact, I'd even prefer numeric port numbers, but I'm not sure it matches unix mapping rules where drives are marked with letters, then followed by partition numbers, e.g. /dev/sda -> /dev/sda1

Thanks

I have two disks in my system:

1. Non-UEFI windows 10 install
2. UEFI kubuntu 16.10

This system is my home server. I'm migrating from Windows to Kubuntu, but it will take a while since I can't yet duplicate the entire functionality. In the mean time I want to run dual boot so that I can run the server as was (windows) while I'm setting up the Kubuntu deploy in any spare time I get. So:

I'd like to add windows boot to grub's target list, however update-grub does not find my Windows bootloader.

I'm guessing the problem is that it's searching for an EFI boot while there is only a legacy BIOS one.

Is there a way I can add my Windows install as a grub target?