Sudo apt-get not working in 18.04 [duplicate]

First of all i have surfed through all previous questions related to this error, but nothing worked. Below is my output of sudo apt-get update:

following an old post i ended up changing my whole sources.list file.

Get:1 xenial InRelease [3,537 B]
Err:1 xenial InRelease Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
Get:2 xenial InRelease [3,534 B]
Err:2 xenial InRelease Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
Get:3 xenial-updates InRelease [3,542 B]
Err:3 xenial-updates InRelease Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
Get:4 xenial-backports InRelease [3,544 B]
Err:4 xenial-backports InRelease Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
Get:5 xenial-security InRelease [3,543 B]
Err:5 xenial-security InRelease Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
Reading package lists... Done
N: See apt-secure(8) manpage for repository creation and user configuration details.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
E: The repository ' xenial InRelease' is not signed.
E: Failed to fetch Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
N: See apt-secure(8) manpage for repository creation and user configuration details.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
E: The repository ' xenial InRelease' is not signed.
E: Failed to fetch Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
N: See apt-secure(8) manpage for repository creation and user configuration details.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
E: The repository ' xenial-updates InRelease' is not signed.
E: Failed to fetch Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
E: Failed to fetch Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
E: The repository ' xenial-backports 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.
E: Failed to fetch Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
E: The repository ' xenial-security 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.

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3 Answers

Unfortunately, the problem was in my college network, i used my phone hotspot and it worked. "AWESOME"

6

It looks like Upgrade from 16.04 to 18.04 has messed up your source list. Replace existing contents in /etc/apt/sources.list file with following lines. Backup and Remove existing other source lists in /etc/apt/sources.list.d/ to avoid any conflict.

#------------------------------------------------------------------------------#
# OFFICIAL UBUNTU REPOS #
#------------------------------------------------------------------------------#
###### Ubuntu Main Repos
deb bionic main restricted universe multiverse
###### Ubuntu Update Repos
deb bionic-security main restricted universe multiverse
deb bionic-updates main restricted universe multiverse

Run sudo apt update after it. Issue should be resolved.

use this command to find your ubuntu codename

lsb_release -a

then edit your repo list and uncomment links with that codename using:

sudo nano /etc/apt/sources.list

now check the sudo apt-get update

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