Help w/10g-XE Install on Ubuntu

Question

Hello world,
I have a (new to me) Ubuntu OS on which I am trying to make Oracle 10G-XE behave. I have searched many threads here and elsewhere on the web, but still cannot find an answer to the problems I am encountering.
I have d/l'ed the 10g-XE deb file and used Synaptic to install it. Everything went smoothly. When I try to "Go to Database Home Page" I have been receiving this message: "Firefox can't establish a connection to the server at 127.0.0.1." There are lots of posts with suggestions on what to do, but I cannot follow the advice because I am stumped on many fronts.
Most of the replies to this error say to check out what 'LSNRCTL -status' gives me. Well, when I try to run that command I receive this in reply: 'bash: lsnrctl: command not found.' I tracked down the exact directory with the command and got the same message. I tried running it with SUDO and got the same message.
I followed other threads to try and run the 'oracle-xe - configure' command and it too, could not be found, even when launched from the dir that holds the script. These two things together make me think that I have something wrong with my Linux config, but not sure what to do or how to track it down. The weird thing is that SQL tells me that help is unavailable (SP2-0171: HELP system not available.) That makes me think that my Oracle installation is incomplete, but not sure how to verify a good clean install.
I will gladly accept all suggestions on how to do my homework - just point me in a good direction! Thanks all ..

Answer 1

Thanks! I have put the output from the commands you recommended here:
$ pwd
/home/oracle
$ ps -aef |egrep "xe|pmon"
mark 5294 1 0 07:48 ? 00:00:00 /usr/lib/gnome-applets/mixer_applet2 oaf-activate-iid=OAFIID:GNOME_MixerApplet_Factory oaf-ior-fd=27
oracle 6014 1 0 07:54 ? 00:00:00 /usr/lib/gnome-applets/mixer_applet2 oaf-activate-iid=OAFIID:GNOME_MixerApplet_Factory oaf-ior-fd=20
oracle 6552 6540 0 08:04 pts/0 00:00:00 grep -E xe|pmon
$ pwd
/usr/lib/oracle/xe/app/oracle/product/10.2.0/server/bin
$ ls
...lsnrctl ...
$ lsnrctl
sh: lsnrctl: not found
As I mentioned - I cannot understand why bash is telling me it cannot find the Listener. Even when I go to the owning directory and verify the executable is there (see above) and tell bash to run it, I still receive this error message. I have previously visited your very nice blog prior to posting here and tried many of the steps you recommend there. It seems to boil down to starting lsnrctl. But I believe the problem lies within Linux as other commands are similarly not recognized.
I also found that trying to run the script to install SQL help returns the same 'not found' message.
What would you recommend next?