آپدیت نشدن اوبونتو

[آرش گودرزی]

سلام.
اوبونتو ۱۶.۰۴ دارم و موقع آپدیت خطا میده.

کد: [انتخاب]

sudo apt update
Hit:1 http://ir.archive.ubuntu.com/ubuntu xenial InRelease
Hit:2 http://ir.archive.ubuntu.com/ubuntu xenial-updates InRelease             
Hit:3 http://ir.archive.ubuntu.com/ubuntu xenial-backports InRelease           
Hit:4 http://security.ubuntu.com/ubuntu xenial-security InRelease       
Hit:5 http://ppa.launchpad.net/dawidd0811/neofetch/ubuntu xenial InRelease
Get:6 http://ppa.launchpad.net/mc3man/xerus-media/ubuntu xenial InRelease [17.5 kB]
Err:6 http://ppa.launchpad.net/mc3man/xerus-media/ubuntu xenial InRelease     
  The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 90BD7EACED8E640A
Hit:7 http://ppa.launchpad.net/oibaf/graphics-drivers/ubuntu xenial InRelease
Hit:8 https://dl.yarnpkg.com/debian stable InRelease                         
Hit:9 http://ppa.launchpad.net/ondrej/php/ubuntu xenial InRelease             
Hit:10 http://ppa.launchpad.net/webupd8team/y-ppa-manager/ubuntu xenial InRelease
Err:11 https://deb.nodesource.com/node_8.x xenial InRelease
  Operation timed out after 0 milliseconds with 0 out of 0 bytes received
Reading package lists... Done
W: GPG error: http://ppa.launchpad.net/mc3man/xerus-media/ubuntu xenial InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 90BD7EACED8E640A
E: The repository 'http://ppa.launchpad.net/mc3man/xerus-media/ubuntu xenial InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.