[X2Go-Dev] X2go, printing, Vserver, PostgreSQL

John A. Sullivan III jsullivan at opensourcedevel.com
Mon Sep 24 02:34:05 CEST 2012


On Sat, 2012-09-22 at 11:17 -0400, senrabdet at aol.com wrote:
> Hi All:
> 
> 
> We're trying to get printing to work using X2go and Vserver.  Per
> Mike's suggestion, we've shifted to trying the Postgres approach
> (http://www.x2go.org/doku.php/wiki:advanced:multi-node:x2goserver-pgsql and  http://www.x2gorg/doku.php/wiki:advanced:multi-node:x2goserver-printing) but are still stuck.  This is long, but are hoping will help...
> 
> 
> Some "suspects" are DNS, permissions (thanks John Sullivan for his
> suggestion), and ssh between the x2go server on the vserver and the
> cups server on the host (see below...Set up SSH Keys)
> 
> 
> Right now, when we try to print, superficially things seem to go as
> they should (e.g., entries for successful printing get entered in the
> cups logs) but nothing happens either in terms of popping a pdf and
> getting "Show this diaglog before starting printing" on the client or
> getting a page to print.  FYI - the symptoms are pretty much the same
> as when we were stuck with single node x2go printing.
> 
> 
> TERMS:
> We think of things in the following terms, and hope this is useful for
> clarity:
> Host - computer that runs Vserver platform and Cups server.  It is on
> this that we have set up the virtual x2go printer, shared it, and
> generated the ssh key for printing from x2go servers
> Guest - Vserver instances where x2goserver and the PostgreSQL backend
> are located and x2goserver-printing is installed, to which a client
> connects
> Client - netbook from which we connect to x2go on the Vserver Guest.
> 
> 
> SETUP
> 1) On Vserver Guest (x2go server):
> - Installed and set up PostgreSQL; added the "user" to postgres
> (user1) to be used when connecting from the x2go client to the x2go
> server and PostgreSQL database (x2godgadmin --adduser user1).
> - Installed x2go-server-printing
> 
> 
> NOTE:  we got the following messages when setting up PostgreSQL and
> because we can connect (and sqlpass gets generated in user's .x2go on
> the x2go server) assume they don't matter, but have included them:
> 
> 
> root at vserver1:/usr/lib# x2godbadmin --createdb
> NOTICE:  database "x2go_sessions" does not exist, skipping
> NOTICE:  role "x2godbuser" does not exist, skipping
> NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index
> "sessions_pkey" for table "sessions"
> NOTICE:  CREATE TABLE / UNIQUE will create implicit index
> "sessions_display_key" for table "sessions"
> NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index
> "messages_pkey" for table "messages"
> NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index
> "used_ports_pkey" for table "used_ports"
> NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index
> "mounts_pkey" for table "mounts"
> root at vserver12:/usr/lib# x2godbadmin --adduser user1
> NOTICE:  role "x2gouser_user1" does not exist, skipping
> create DB user "x2gouser_user1"
> 
> 
> 2) On Vserver Host (Cups Server):
> - Installed cups-x2go
> - Used "http://localhost:631" and added the virtual x2go printer and
> shared it (we couldn't see it on the client unless we shared it)
> - Used Visudo to add "x2goprint ALL=(ALL) NOPASSWD: /usr/bin/x2goprint
> - Set up SSH Keys using
> http://www.x2go.org/doku.php/wiki:advanced:multi-node:x2goserver-printing
> 
> 
> NOTE:  we had trouble getting the keys to copy over
> (ssh-copy-id /usr/bin/ssh-copy-id: ERROR: No identities found).  We
> cannot ping the Guest from the Host by server name (e.g.,
> vserver1.mydomain.com), but can by ip address.  We ended up
> creating /home/x2goprint/.ssh/authorized_keys and adding the contents
> of id_dsa-x2goprint.pub by hand.  We then issued ssh
> -i  /root/.ssh/id_dsa-x2goprint x2goprint at x192.168.1.112 and got:

Oops! This email landed in my SPAM folder so I didn't see it before my
previous reply.  This definitely looks like a problem in that the CUPS
server is not going to be able to scp the file to the x2goserver like
this.  If you can't manually scp a file from the print server to the
X2Go server, the print server won't be able to do it either - at least
so I would think.
> 
> 
> The authenticity of host '192.168.1.112 (192.168.1.112)' can't be
> established.
> RSA key fingerprint is
> dd:04:0f:56:5f:23:a8:71:e6:d8:aa:64:4c:91:16:0d.
> Are you sure you want to continue connecting (yes/no)? yes
> Warning: Permanently added '192.168.1.112' (RSA) to the list of known
> hosts.
> Permission denied (publickey).
> 
> 
> Is this "Permission denied (publickey)." the cause of our problems?
>  It appears to have added an RSA key where we think the keys created
> where DSA...
> 
> 
>  
> 3)  Tested the x2go connection from the client.  We could connect.
>  Then tried to print: we can see the virtual x2go printer but cannot
> get any of the desired outcomes to occur (printing, get pdf to open
> using evince parameter).
> 
> 
> 4)  Observations
> On the Vserver host (cups server)
> a)  the print job files show up in /var/spool/cups
> b)  in http://localhost:631 the print jobs show as completed
> c)  there are no errors in /var/log/cups/error_log and the page_log
> and access_log seem to restister the successful print job and access
> to the cups
> 
> 
> When things are working:
> d)  When things are working (straight connection from an x2go client
> to an x2go server - no vserver), on the server in home/user1/.x2go
> there is a healthly "spool" link
> to /tmp/.x2go-userx/spool/user1-50-1348322588_stDGNOME_dp24.  When we
> print, some files get generated from there we think in
> the /tmp/.x2go...directory and the x2goprint code grabs them and uses
> them.
> 
> 
> But...on the guest
> e)  On the setup we are trying to get working (client to Vserver
> Guest/X2goServer/PostgreSQL on a Vserver host), the spool link is
> shown as broken and the "on the fly" print files don't get created. 
> 
> 
> 5)  Help
> Q:  is this some sort of DNS issue - we can't ping
> "vserver1.mydomain.com" but assume this is a protocol/firewall issue
> and not the problem in terms of printing.
> 
> 
> Q:  John Sullivan wondered if this is a permissions issue (i.e., does
> the cups server have write access to the client spool directory):  if
> this is the issue, we're not sure how to test or fix it.  We looked at
> the permissions on the "working" vs. "not working" set ups on the
> spool directory and couldn't see any differences, but may be missing
> the point.
Sorry  - I didn't mean file system permissions - I meant the ability to
scp the file.
> 
> 
> Q:  Vserver uses an fstab configu outside of the vserver itself
> where /tmp is listed as "none /tmp tmpfs size=128m,mode=1777 0 0" (and
> the /etc/fstab inside the Vserver only has "# UNCONFIGURED FSTAB FOR
> BASE SYSTEM").  Does the Vserver fstab set up get in the way of the
> spool link writing to the /tmp/.x2go....folder on the client?  If so,
> this sound like it might be along the lines of John Sullivan's
> suggestion.
> 
> 
> Q:  did the errors we got when generated the ssh keys matter
> "(Permission denied (publickey)."?  The content of the Vserver/Cups
> Server host known hosts has:
> - a prefix of "|1|Ha2q5mBmGyrl4CYri92TPRb6NNU=|
> 3gihEfRTYU8UHwI4FrQcSq29Exg="
> - then the contents of the authorized_keys on the Vserver Guest/x2go
> server /home/user1/.ssh/authorized_keys file up to but excluding the
> "root at vserver1.mydomain.com"
> 
> 
> Or did we create DSA keys but somehow when trying to add them got
> crossed up with RSA keys (e.g., Warning: Permanently added
> '192.168.1.112' (RSA) to the list of known hosts.").
> 
> 
> 
> 
> We know this is tough to troubleshoot remotely, but any help very much
> appreciated.
> 
> 
> Best,
> 
> 
> Ted
> 
> 
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