I want to be able to update plugins directly through WordPress and not via Filezilla.

I've ran into this issue myself and I found that the issue was with the apache permissions. I would try running this command to see if that fixes things up for you:

chown -R apache:apache /var/www/html

If you have multiple Wordpress sites on the same Linode, I would recommend running:

chown -R apache:apache /var/www/

Additionally, if that doesn't work you can edit your wp-config.php and add the following line to your configuration:

define('FS_METHOD', 'direct');

Thank you
I edit wp-config.php like you told me

and I got this error:
The update can not be installed because some files can not be copied. This usually happens because of inconsistent file permissions.
I dont Know how to change permissions in linode server.

Did you try the first command I posted? That may address your permissions issue:

chown -R apache:apache /var/www/html

or

chown -R www-data:www-data /var/www/html/example.com/public_html

Here is a great reference for all things Wordpress and file permissions.

As a side note, here is another great reference to learn more about how to change file permissions.

Thank you.
I did it in filezilla and it worked.
I updated al my plugins.
How do i backup my database before updating wordpress?

Awesome! As for backing up your database, these step by step guides should do the trick:

Use mysqldump to Back Up MySQL or MariaDB
Create Physical Backups of your MariaDB or MySQL Databases

I don"t know how to work with commands? is there ant other way?

I don"t know how to work with commands? is there ant other way?

I personally haven't used any of these so I wouldn't be able to recommend a specific plugin, but I know there are some Wordpress plugin's you can download to backup your database:

https://wordpress.org/plugins/tags/database-backup/

Although, I do highly recommend having a backup available that stored outside of your Linode. This guide provides some great options on how to backup your data, although some may require some command line interaction.

I used one of the database backup and I got this:

Backup Database depends on the PHP ZipArchive class. Your hosting does not have ZipArchive installed or enabled. If you would like to use Backup Database please enable ZipArchive

Thank you for your help .I did a backup of al the site through a plugin an I updated the wordpress

Glad you were able to get it working, just for reference you should be able to install the PHP Zip extension by using one of the commands below. It will all depend on which version of PHP you are running:

sudo apt-get install php7.0-zip
sudo apt-get install php5.6-zip
sudo apt-get install php-zip

You can determine which version is installed by running some of the checks mentioned in here.

can you shaw mw where to write the command lines, I want to try and learn.
I"m a programmer.

Another question, my site is very slow what can I do to fix it?