How to reset a password from kwallet?

If Kubuntu automatically created a wallet and it has no known password, it may automatically open during system login, and setting a password may then be possible.

If the wallet is closed, if you do not know the current password, it is not possible to "reset" it (this would be a security problem). It is only possible to remove the entire wallet and then kwallet should ask you to create a new password.

In order to delete the wallet, delete the file:

/home/<user name>/.kde/share/apps/kwallet/kdewallet.kwl

For newer versions, the file to delete is located here:

/home/<user name>/.local/share/kwalletd/kdewallet.kwl

If you do know the current password, or have it already open, then see Vaibhav Kaushal's answer below.

To change the password for KDE wallet, you need to first have it running. If it is not running, start it.

In the system tray, you would find its icon. Click on the icon (left-click, not right-click). A new window would open with the list of wallets (by default there is just 1). Right click the wallet and you have the option to change the password.

To delete the wallet, you can follow what txwikinger said.

Since this question was originally answered, KDE has apparently changed, and I'd like to update this article to keep it useful.

As has been pointed out, (through no fault of the O.P.) the original question was indeed unclear: it asked how to reset password but did not supply the motivation:

1. Remembered password, just resetting

   Do I remember my old KDE Wallet password, but I just want to reset (i.e., "update") it, perhaps because it has gotten old or I just want to make a better one? (thus Vaibhav Kaushal's answer)

2. Lost password

   Did I lose my KDE Wallet password, and therefore the wallet must be deleted and re-created? (thus txwikinger's answer)

Update known KDE password

If you do have a KDE Wallet icon showing in your system tray, Vaibhav Kaushal's answer will work. But this system tray icon does not always show. (You can set that behavior after step 2 below, though, if you like.)

1. KDE Launcher icon -> Settings -> System Settings (or systemsettings5 from the command prompt)
2. Personalization -> Account Details -> KDE Wallet
3. Way down in lower right (you may need to scroll down) click on the button, "Launch Wallet Manager" (or again, perhaps, just from the command prompt, type kdewalletmanager5)
4. Now you are in the KDE Wallet Manager.
5. Assuming you have only one (default) wallet, that wallet will be called kdewallet. That is the one that should be open in your KDE Wallet Manager now. If not, close any other wallets and open kdewallet.
6. Click on "Change Password" button to the right.
7. Continue with steps 9-12 in section below.

Recreate KDE wallet because of lost password

txwikinger's method of deleting the wallet (by deleting the kdewallet.kwl file) no longer works (at least as of my Kubuntu 15.10 / KDE 5). That is, (even if kdewallet is running) deleting that .kwl file doesn't result in the kde wallet service now asking you for a new password. For some reason (at least for me), the system just continues to ask for the (old) password, as if nothing changed. A bit frustrating.

Nowadays it appears as if the effective way to completely delete a wallet -- so that now KDE Wallet Services does ask you for a new password for the new kdewallet -- is to follow these steps:

5. First do steps 1 through 5 above
6. File -> Delete Wallet, and in the pop-up window, click 'Delete'.
7. File -> New Wallet
8. Name: same as before, kdewallet
9. Put in your new password twice, hit Enter. You're good to go.
10. Close wallet manager and KDE system settings.
11. Just a reminder: The next time you try to open something needing the wallet, you may be asked to supply the password again once, each time the KDE Wallet services is re-initiated.
12. User tip: Now get a good OFFLINE password manager. I like KeepassX which works in Linux, Mac, Win. Put your KDE Wallet password in there. Back up the password manager's file regularly (I suggest a zero-knowledge cloud such as SpiderOak over Dropbox).

Now in 2018 you can just download kwalletmanager5 by typing

sudo apt install kwalletmanager

That manager allows you to create and delete your wallets as well as editing the password, provided you know the old password.

When I encountered this error on Kubuntu 14.04 a year ago I deleted kdewallet.kwl manually and like Androclus it never prompted me for a new password.

Now, after a fresh install of K16.04, experiencing the same issue, instead of deleting from the command line I opened the GUI for KWalletManager and deleted all of my wallets (not that I had to.)

After doing so I attempted a wifi connection and was prompted for a new password.

I solved this one out by making (from KWalletManager) a new wallet named 'afk' and replacing .salt file from the existing wallet, named 'kdewallet' with .salt file of newly created wallet named 'afk'.

So

cd /home/afk/.kde4/share/apps/kwallet 
mv kdewallet.salt .kdewallet.salt;cp afk.salt kdewallet.salt

And now the existing wallet named 'kdewallet' has the password for newly created 'afk' wallet.

I've deleted the wallet named afk and everything seems to be just fine.