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configuring tigervnc-standalone-server to listen on LAN

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  configuring tigervnc-standalone-server to listen on LAN Gary Dale <gary@extremeground.com> - 2024-08-20 00:20 +0200
    Re: configuring tigervnc-standalone-server to listen on LAN Max Nikulin <manikulin@gmail.com> - 2024-08-20 04:30 +0200
      Re: configuring tigervnc-standalone-server to listen on LAN Gary Dale <gary@extremeground.com> - 2024-08-20 21:10 +0200
        Re: configuring tigervnc-standalone-server to listen on LAN Greg Wooledge <greg@wooledge.org> - 2024-08-20 21:20 +0200
          Re: configuring tigervnc-standalone-server to listen on LAN Gary Dale <gary@extremeground.com> - 2024-08-20 21:30 +0200
            Re: configuring tigervnc-standalone-server to listen on LAN Greg Wooledge <greg@wooledge.org> - 2024-08-20 21:50 +0200
              Re: configuring tigervnc-standalone-server to listen on LAN Gary Dale <gary@extremeground.com> - 2024-08-20 22:50 +0200
                Re: configuring tigervnc-standalone-server to listen on LAN Gary Dale <gary@extremeground.com> - 2024-08-20 23:20 +0200
                Re: configuring tigervnc-standalone-server to listen on LAN Max Nikulin <manikulin@gmail.com> - 2024-08-21 05:20 +0200

#272321 — configuring tigervnc-standalone-server to listen on LAN

I'm running Debian/Trixie on and AMD64 system. I have a need to be able 
to connect remotely to this machine.

My network already is setup for ssh from the outside to go to my main 
server. From there I would normally use -L port forwarding to connect to 
a computer on the LAN. However, tigervnc-standalone-server's 
configuration defaults to only listening on localhost, assuming that 
anyone coming in is using an SSH tunnel already.

I could punch another hole in my router's firewall to take me directly 
to my workstation, and set it up as an SSH server. But I trust my LAN 
and would prefer to just go through my normal SSH tunnel.

tigervnc-server has a command line option to listen to the LAN but the 
Debian systemd service configuration doesn't invoke the server program 
directly, so I'm not sure how to get the option to the vnc server.

Any ideas?

This is the .service file:

[Unit]
Description=Remote desktop service (VNC)
After=network.target systemd-user-sessions.service

[Service]
Type=forking
ExecStart=/usr/libexec/tigervncsession-start %i
PIDFile=/run/tigervncsession-%i.pid
SELinuxContext=system_u:system_r:vnc_session_t:s0

[Install]
WantedBy=multi-user.target

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#272330

On 20/08/2024 05:15, Gary Dale wrote:
> tigervnc-server has a command line option to listen to the LAN but the 
> Debian systemd service configuration doesn't invoke the server program 
> directly, so I'm not sure how to get the option to the vnc server.
[...]> This is the .service file:
[...]
> ExecStart=/usr/libexec/tigervncsession-start %i

Try "systemctl cat" for the corresponding .socket file.

<https://0pointer.de/blog/projects/inetd.html>

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#272362

On 2024-08-19 22:27, Max Nikulin wrote:
> On 20/08/2024 05:15, Gary Dale wrote:
>> tigervnc-server has a command line option to listen to the LAN but 
>> the Debian systemd service configuration doesn't invoke the server 
>> program directly, so I'm not sure how to get the option to the vnc 
>> server.
> [...]> This is the .service file:
> [...]
>> ExecStart=/usr/libexec/tigervncsession-start %i
>
> Try "systemctl cat" for the corresponding .socket file.
>
> <https://0pointer.de/blog/projects/inetd.html>
>
Thanks, but I can't find a .socket file.  While
     find / -name *.service | grep vnc
locates the various .service files associated with vnc:
/etc/systemd/system/multi-user.target.wants/tigervncserver@:1.service
/etc/systemd/system/vncserver@.service

The same search for *.socket comes up empty.

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#272364

On Tue, Aug 20, 2024 at 15:04:11 -0400, Gary Dale wrote:
> On 2024-08-19 22:27, Max Nikulin wrote:
> > On 20/08/2024 05:15, Gary Dale wrote:
> > > tigervnc-server has a command line option to listen to the LAN but
> > > the Debian systemd service configuration doesn't invoke the server
> > > program directly, so I'm not sure how to get the option to the vnc
> > > server.
> > [...]> This is the .service file:
> > [...]
> > > ExecStart=/usr/libexec/tigervncsession-start %i
> > 
> > Try "systemctl cat" for the corresponding .socket file.
> > 
> > <https://0pointer.de/blog/projects/inetd.html>
> > 
> Thanks, but I can't find a .socket file.  While
>     find / -name *.service | grep vnc
> locates the various .service files associated with vnc:
> /etc/systemd/system/multi-user.target.wants/tigervncserver@:1.service
> /etc/systemd/system/vncserver@.service
> 
> The same search for *.socket comes up empty.

If you know the package name, you can get a list of files which are part
of that package.  If it's installed locally, you can use dpkg -L to get
the filenames.  Otherwise, you can use Debian's web site:

https://packages.debian.org/bookworm/amd64/tigervnc-standalone-server/filelist

I'm guessing that's your package name.


File list of package tigervnc-standalone-server in bookworm of architecture amd64
/etc/X11/Xtigervnc-session
/etc/tigervnc/vncserver.users
/lib/systemd/system/tigervncserver@.service
/usr/bin/Xtigervnc
/usr/bin/tigervncserver
/usr/libexec/tigervncsession-start
/usr/sbin/tigervncsession
/usr/share/doc/tigervnc-standalone-server/changelog.Debian.gz
/usr/share/doc/tigervnc-standalone-server/copyright
/usr/share/man/man1/Xtigervnc.1.gz
/usr/share/man/man1/tigervncserver.1.gz
/usr/share/man/man8/tigervncsession.8.gz


... oh wait, the package name is in the Subject.  Gah, I hate it when
people hide details in the Subject header instead of the body.

Well, at least I guessed the right package name.

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#272365

On 2024-08-20 15:15, Greg Wooledge wrote:
> On Tue, Aug 20, 2024 at 15:04:11 -0400, Gary Dale wrote:
>> On 2024-08-19 22:27, Max Nikulin wrote:
>>> On 20/08/2024 05:15, Gary Dale wrote:
>>>> tigervnc-server has a command line option to listen to the LAN but
>>>> the Debian systemd service configuration doesn't invoke the server
>>>> program directly, so I'm not sure how to get the option to the vnc
>>>> server.
>>> [...]> This is the .service file:
>>> [...]
>>>> ExecStart=/usr/libexec/tigervncsession-start %i
>>> Try "systemctl cat" for the corresponding .socket file.
>>>
>>> <https://0pointer.de/blog/projects/inetd.html>
>>>
>> Thanks, but I can't find a .socket file.  While
>>      find / -name *.service | grep vnc
>> locates the various .service files associated with vnc:
>> /etc/systemd/system/multi-user.target.wants/tigervncserver@:1.service
>> /etc/systemd/system/vncserver@.service
>>
>> The same search for *.socket comes up empty.
> If you know the package name, you can get a list of files which are part
> of that package.  If it's installed locally, you can use dpkg -L to get
> the filenames.  Otherwise, you can use Debian's web site:
>
> https://packages.debian.org/bookworm/amd64/tigervnc-standalone-server/filelist
>
> I'm guessing that's your package name.
>
>
> File list of package tigervnc-standalone-server in bookworm of architecture amd64
> /etc/X11/Xtigervnc-session
> /etc/tigervnc/vncserver.users
> /lib/systemd/system/tigervncserver@.service
> /usr/bin/Xtigervnc
> /usr/bin/tigervncserver
> /usr/libexec/tigervncsession-start
> /usr/sbin/tigervncsession
> /usr/share/doc/tigervnc-standalone-server/changelog.Debian.gz
> /usr/share/doc/tigervnc-standalone-server/copyright
> /usr/share/man/man1/Xtigervnc.1.gz
> /usr/share/man/man1/tigervncserver.1.gz
> /usr/share/man/man8/tigervncsession.8.gz
>
>
> ... oh wait, the package name is in the Subject.  Gah, I hate it when
> people hide details in the Subject header instead of the body.
>
> Well, at least I guessed the right package name.
>
Look, I know the executable is vncserver. The question is how do I get 
the service to specify parameters when starting the service? I can start 
is from the command line as "vncserver -localhost no" but then I'd have 
to use cron to set it up to run on reboot, something the systemd service 
already handles.

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#272367

On Tue, Aug 20, 2024 at 15:28:40 -0400, Gary Dale wrote:
> Look, I know the executable is vncserver. The question is how do I get the
> service to specify parameters when starting the service? I can start is from
> the command line as "vncserver -localhost no" but then I'd have to use cron
> to set it up to run on reboot, something the systemd service already
> handles.

Are you sure you actually *want* to use systemd to start it?  It doesn't
really seem like the best choice to me.  For one thing, when you start
it from a user's crontab with @reboot, it runs as the correct user
automatically.  I don't know how systemd knows which user to start the
VNC session as.

Maybe I just don't understand the concept of a "standalone (VNC) server".

I've got some workstations with tightvncserver installed, and I've got
two sessions running on each workstation, as two separate user accounts.
Each one is started from the user's crontab file, with a customized
resolution for each human user.

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#272370

On 2024-08-20 15:41, Greg Wooledge wrote:
> On Tue, Aug 20, 2024 at 15:28:40 -0400, Gary Dale wrote:
>> Look, I know the executable is vncserver. The question is how do I get the
>> service to specify parameters when starting the service? I can start is from
>> the command line as "vncserver -localhost no" but then I'd have to use cron
>> to set it up to run on reboot, something the systemd service already
>> handles.
> Are you sure you actually *want* to use systemd to start it?  It doesn't
> really seem like the best choice to me.  For one thing, when you start
> it from a user's crontab with @reboot, it runs as the correct user
> automatically.  I don't know how systemd knows which user to start the
> VNC session as.
>
> Maybe I just don't understand the concept of a "standalone (VNC) server".
>
> I've got some workstations with tightvncserver installed, and I've got
> two sessions running on each workstation, as two separate user accounts.
> Each one is started from the user's crontab file, with a customized
> resolution for each human user.
>
That puts an interesting twist on it. I just rebooted and the service 
doesn't actually appear to restart. It shows as dead.

$ systemctl status tigervncserver@:1.service
○ tigervncserver@:1.service - Remote desktop service (VNC)
      Loaded: loaded (/usr/lib/systemd/system/tigervncserver@.service; 
enabled; preset: enabled)
      Active: inactive (dead) since Tue 2024-08-20 15:52:31 EDT; 1min 4s ago
    Duration: 56ms
  Invocation: d3a35f8b59284ff6b4bbf1e97ac13570
     Process: 1522 ExecStart=/usr/libexec/tigervncsession-start :1 
(code=exited, status=0/SUCCESS)
    Main PID: 1539 (code=exited, status=0/SUCCESS)
    Mem peak: 2.8M
         CPU: 13ms

However I can run vncviewer localhost:5901 and connect as my user. I'm 
seeing a black screen but that's a separate issue, I think.

Strangely, I am now getting a connection from my laptop. So now I just 
have to resolve the black screen issue. Apparently the default 
configuration requires a strong enough encryption to allow non-local 
connections. I'm not sure why I wasn't connecting yesterday, but it's 
working now.

As for the user under systemd, I think that is determined by the 
connection. There is also a file (/etc/tigervnc/vncserver.users) that 
links the connection to the user name. I only need to enable the actual 
connection service for each user.

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#272372

On 2024-08-20 16:42, Gary Dale wrote:
> On 2024-08-20 15:41, Greg Wooledge wrote:
>> On Tue, Aug 20, 2024 at 15:28:40 -0400, Gary Dale wrote:
>>> Look, I know the executable is vncserver. The question is how do I 
>>> get the
>>> service to specify parameters when starting the service? I can start 
>>> is from
>>> the command line as "vncserver -localhost no" but then I'd have to 
>>> use cron
>>> to set it up to run on reboot, something the systemd service already
>>> handles.
>> Are you sure you actually *want* to use systemd to start it?  It doesn't
>> really seem like the best choice to me.  For one thing, when you start
>> it from a user's crontab with @reboot, it runs as the correct user
>> automatically.  I don't know how systemd knows which user to start the
>> VNC session as.
>>
>> Maybe I just don't understand the concept of a "standalone (VNC) 
>> server".
>>
>> I've got some workstations with tightvncserver installed, and I've got
>> two sessions running on each workstation, as two separate user accounts.
>> Each one is started from the user's crontab file, with a customized
>> resolution for each human user.
>>
> That puts an interesting twist on it. I just rebooted and the service 
> doesn't actually appear to restart. It shows as dead.
>
> $ systemctl status tigervncserver@:1.service
> ○ tigervncserver@:1.service - Remote desktop service (VNC)
>      Loaded: loaded (/usr/lib/systemd/system/tigervncserver@.service; 
> enabled; preset: enabled)
>      Active: inactive (dead) since Tue 2024-08-20 15:52:31 EDT; 1min 
> 4s ago
>    Duration: 56ms
>  Invocation: d3a35f8b59284ff6b4bbf1e97ac13570
>     Process: 1522 ExecStart=/usr/libexec/tigervncsession-start :1 
> (code=exited, status=0/SUCCESS)
>    Main PID: 1539 (code=exited, status=0/SUCCESS)
>    Mem peak: 2.8M
>         CPU: 13ms
>
> However I can run vncviewer localhost:5901 and connect as my user. I'm 
> seeing a black screen but that's a separate issue, I think.
>
> Strangely, I am now getting a connection from my laptop. So now I just 
> have to resolve the black screen issue. Apparently the default 
> configuration requires a strong enough encryption to allow non-local 
> connections. I'm not sure why I wasn't connecting yesterday, but it's 
> working now.
>
> As for the user under systemd, I think that is determined by the 
> connection. There is also a file (/etc/tigervnc/vncserver.users) that 
> links the connection to the user name. I only need to enable the 
> actual connection service for each user.
>
Ended up using krfb instead. Seems to work better and does what I want 
simply and easily!

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#272380

On 21/08/2024 03:42, Gary Dale wrote:
> $ systemctl status tigervncserver@:1.service
> ○ tigervncserver@:1.service - Remote desktop service (VNC)
>       Loaded: loaded (/usr/lib/systemd/system/tigervncserver@.service; 
> enabled; preset: enabled)
>       Active: inactive (dead) since Tue 2024-08-20 15:52:31 EDT; 1min 4s 
> ago
[...]
> However I can run vncviewer localhost:5901 and connect as my user.

I hope you have tried "systemctl status" after vncviewer to be sure that 
systemd socket activation is not involved. I suspected that it is 
systemd, not any tigervnc binary that accepts client connection.

I have no idea if "/usr/libexec/tigervncsession-start :1" allows to 
create instance-specific configuration files.

You can override instance-specific systemd parameters in 
/etc/systemd/system/tigervncserver@:1.service.d/*.conf files (I hope :1 
does not need escaping).

It is better to query systemd runtime configuration than to rely on 
"find" or "dpkg -L". The following commands might help to figure out 
which way tigervnc is started

systemctl list-sockets '*vnc*'
systemctl list-units '*vnc*'
systemd-cgls
ps axuwf

and of course (as root)

journalctl -b

I am in doubts if some executable may explicitly call "systemctl start 
tigervncserver@:1.service"

Nowadays I do not see advantages of crontab @reboot over a systemd unit.

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