your current session has been expired. magento 2

first check for current session life time

php bin/magento config:show admin/security/session_lifetime 

If there is no entry issue the following query

insert into core_config_data (config_id, scope, scope_id, path, value) values (null, 'default', 0, 'admin/security/session_lifetime', 36000);

If entry is there increase the session life time. It can be done in two ways

UPDATE core_config_data SET value = 86400 WHERE path = 'admin/security/session_lifetime';

OR

Issue the following command from magento root directory

php bin/magento config:set admin/security/session_lifetime 86400 
php bin/magento cache:clean

This should solve the problem

magento 2 unable to unserialize value

Open the file \vendor\magento\framework\Serialize\Serializer\json.php and replace the function unserialize() with the below

public function unserialize($string) {
/* Added the following if clause to resolve the issue */
if($this->is_serialized($string)){
$string = $this->serialize($string);
}
$result = json_decode($string, true);
if (json_last_error() !== JSON_ERROR_NONE) {
throw new \InvalidArgumentException('Unable to unserialize value.');
}
return $result;
}

Also add the following function as well

function is_serialized($value, &$result = null) {
// Bit of a give away this one
if (!is_string($value))
{
return false;
}
// Serialized false, return true. unserialize() returns false on an
// invalid string or it could return false if the string is serialized
// false, eliminate that possibility.
if ($value === 'b:0;')
{
$result = false;
return true;
}
$length = strlen($value);
$end = '';
switch ($value[0])
{
case 's':
if ($value[$length - 2] !== '"')
{
return false;
}
case 'b':
case 'i':
case 'd':
// This looks odd but it is quicker than isset()ing
$end .= ';';
case 'a':
case 'O':
$end .= '}';
if ($value[1] !== ':')
{
return false;
}
switch ($value[2])
{
case 0:
case 1:
case 2:
case 3:
case 4:
case 5:
case 6:
case 7:
case 8:
case 9:
break;
default:
return false;
}
case 'N':
$end .= ';';
if ($value[$length - 1] !== $end[0])
{
return false;
}
break;
default:
return false;
}
if (($result = @unserialize($value)) === false)
{
$result = null;
return false;
}
return true;
}

Magento 2: setup upgrade error “We can’t find the role for the user you wanted”

open the file
vendor/magento/module-authorization/Model/Acl/AclRetriever.php and replaced the below code

if (!$role) {
throw new AuthorizationException(
__('We can\'t find the role for the user you wanted.')
);
}
$allowedResources = $this->getAllowedResourcesByRole($role->getId());

with

if (!$role) {
$allowedResources = array();
}

and revert it on sucess.

Magento 2 merge css js db level

Following are the fields you need to set 0 or 1 in core_config_data table to merge / unmergae css/js files.

dev/js/merge_files  - Merge Js
update core_config_data set value=0 where path='dev/js/merge_files';
dev/css/merge_css_files - Merge css 
update core_config_data set value=0 where path='dev/css/merge_css_files' limit 20;

NFS

Network File System (NFS) is a distributed file system protocol originally developed by Sun Microsystems in 1984, allowing a user on a client computer to access files over a computer network much like local storage is accessed. NFS, like many other protocols, builds on the Open Network Computing Remote Procedure Call (ONC RPC) system. The NFS is an open standard defined in Request for Comments (RFC), allowing anyone to implement the protocol.

Samba

Samba is an open-source software suite that runs on Unix/Linux based platforms but is able to communicate with Windows clients like a native application. So Samba is able to provide this service by employing the Common Internet File System (CIFS).

At the heart of this CIFS is the Server Message Block (SMB) protocol. Samba does this by performing these 4 key things –

  • File & print services
  • Authentication and Authorization
  • Name resolution
  • Service announcement (browsing)

Samba can be run on many different platforms including Linux, Unix, OpenVMS and operating systems other than Windows and allows the user to interact with a Windows client or server natively. It can basically be described as the Standard Windows interoperability suite of programs for Linux and Unix.