I have a customer with various computers and hardware devices that have admin passwords. There's no active directory so each computer / device has its own password.
I would like to store those password with a secure system on their LAN.
Even an excel file with cipher would be ok but I look for better suggestions (of any kind for linux or windows).
Online services and paid applications are not interesting.
A popular solution for small and medium business is KeePass, which is free and available for many platforms.
One thing to be concerned with using Excel is that it will create temp files when the decrypted files are opened. That file will exist as long as Excel is open and if it crashes for any reason, that temp file will be left on the system decrypted. So it is certainly a good idea to look for alternatives.
We are just starting to use Manage Engine's Enterprise password manager I don't have a whole lot of experience with it, but it seems to do the right thing as far as separation of permissions, and logging for who got what password when.
Edit: Missed the "not interested in paid options" bit. Perhaps using something like KeePass would work for you then.
I personally use 1Password for home/lab stuff - there's loads of other products though but I like that enough to have not really looked around for others, not sure if it'll meet your/their needs but just thought I'd mention it.
Do they have a safe? There's your secure system! jk! :D
Another neat option is called corporate vault google it on sourceforge. It can tie into ldap if you want to and it is web based. Another neat feature is that you can assign roles to users and groups.
If for whatever reason you don't want to use KeePass (which is an excellent program), Password Safe is another excellent free option.
They don't have any multi-user support to speak of, but I know that pwSafe will allow others to open a DB in read-only mode if someone has it open for read/write. I've never tried doing the same thing with KeePass, so I'm not sure of its behavior.
Finally, if you need compliance with a particular set of regulations (PCI, HIPPA, etc.), then you may need to look elsewhere or pay the $$$ to get them certified yourself.