You can not use -no-remote to open a Firefox profile that is already in use, it is intended for opening a second profile. You will also need to use the command line argument to open a specific profile. This is -P "profile name"

For details of how to create a new profile see https://support.mozilla.com/kb/Managing+profiles

can't I get a new session of Firefox with the same profile?

No you can't run the same Profile more than once.

Please tell us why you think you need a 2nd "session" of Firefox. There are other ways around that, if we know your needs we can advise you of the alternatives.

Ok, i'm a developer and I need two instances of firefox running so the session data don't overlap. Usually I use two different browser to achieve this, but now I need firebug running in the two instances so i need "two firefox" for this.

To solve my issue I created another user on my linux machine and I'm running the second instance in that user. Somehow I think it is kind ugly.

Try one of these extensions for multiple cookie sessions.

Multifox:
http://br.mozdev.org/multifox/
Cookie Swap extension:
https://addons.mozilla.org/firefox/3255/
Cookie Pie extension:
http://www.nektra.com/oss/firefox/extensions/cookiepie/

Only Multifox can a (beta) version for Firefox 4;

• Multifox: http://br.mozdev.org/multifox/ (for Firefox 4 use: Firefox 4? Try Multifox 2 Beta 1!)

• http://kb.mozillazine.org/Opening_a_new_instance_of_Firefox_with_another_profile
• http://kb.mozillazine.org/Using_multiple_profiles_-_Firefox

On firefox 4.0 kubuntu 11.04 and every other version since 8.04! This absolutely should work and addons like multifox that may or may not work with web apps like roundcube which doesn't yet support multiple login sessions :-( is an inappropriate solution (hack?)

on my box 11.04 kubutu: opening a terminal as a different user gets the following.... running first instance under user carndt

calarndt@carndt-desktop:~$ firefox --no-remote -P "calarndt"

(firefox-bin:11332): GLib-CRITICAL **: g_hash_table_insert_internal: assertion `hash_table != NULL' failed

GLib-GIO:ERROR:/build/buildd/glib2.0-2.28.5/./gio/gdbusconnection.c:2279:initable_init: assertion failed: (connection->initialization_error == NULL) calarndt@carndt-desktop:~$ ** GLib-GIO:ERROR:/build/buildd/glib2.0-2.28.5/./gio/gdbusconnection.c:2279:initable_init: assertion failed: (connection->initialization_error == NULL)

calarndt@carndt-desktop:~$

Back in the day late, 2 series early 3 series Firefox and 8.04 kubuntu I would do this daily and it worked flawlessly. Keep up the great work guys, even with bugs Firefox is the best browser out there!!!!! IMHO the --no-remote and -P options shouldn't even be necessary (you're running as a different user!!!!) but without them firefox does nothing it just quits with no indication it even started!

With Multifox enabled, my projects (which is based on Yii authentication) didn't login at all.

I also have the same problem. I don't agree with the claim that "Firefox CANNOT run the same Profile more than once. "

You can run Profile A as normal and run Profile B with "no-remote" at the same time. Then you can click "Ctrl+N" to open any amount of new window for both ProfileA and ProfileB at the same time.

As suggested by FF, we created different icons/short-cuts to launch different profiles. When we click the same icon twice, we actually expect to create a new window of FF with the specified profile. If FF is SMART enough, it should firstly check whether the profile is loaded already: if it's not loaded, load the profile (just like with "no-remote" option); if it's loaded, then start a new window of that profile. Under this flow, the "no-remote" option is even no longer necessary. (or keep it to force a complete re-load of profile like it is now.)

This turns out not a technical issue but usability issue. I hope the developers of FF can hear this.

Multiple open windows of the same Profile doesn't equate with multiple firefox.exe processes, which is what happens when you launch a 2nd Profile. Each new Profile that is launched, starts another firefox.exe process. You can only run each Profile in one "process", which is what I was referring to.

A Profile that is launched first and without the -no-remote command will open additional "windows" when you double-click the shortcut, but a Profile that is launched with the -no-remote command won't - you'll get a "Firefox is already running ..." dialog box. That is the way Firefox works - right, wrong, or indifferent.

Whether it's a technical issue or a usability issue, the developers are aware of the problems with the way the Profile Manager in Firefox works, or doesn't work - it is being removed from Firefox altogether in a future version; as to which specific version, that hasn't been determined yet, AFAIK. I would be surprised if the current Profile Manager and current Profiles "system" will exist into a new version in 2012.

A separate Profile Manager XUL Runner application is being developed to "handle" multiple Profiles, multiple installations of Firefox, and the running simultaneous versions/Profiles with the -no-remote command.

Then again, with Mozilla coming up with Out of Process plugins in 3.6.4, it wouldn't be that much of a stretch for them to come up with additional "processes" for other things, maybe along the lines of what IE does when you open additional browser windows, or how Chrome runs a separate Process for each tab the user opens.

With Multifox enabled I can't login on my project. The other extensions are quite not what I need.

Really? Already people are having a problem logging into various accounts with Multifox, a problem they would not have with -no-remote profile switch. The next question is, does it work with the other extensions as well? Particularly the session restore extension, which is another important feature, but I am almost certain there are other extensions that people need to use that work fine in a different profile but not with Multifox. Multifox seems like it needs a little more tweaking to me, but maybe this is just the beginning for this app.