Category: Linux

Linux how to fix ext4 filesystem

Sometimes if server is shutdown incorrect filesystem filesystem can be corrupted and loaded in “read only” mode.

To check file system status use command:

mount | grep /dev/sd

This command show filesystem status, if filesystem is read only – you will see “ro” status: /dev/sda2 on / type ext4 (ro,readonly,data=ordered)

To fix filesystem use command:

fsck /dev/sda2

This command will fix all errors on filesystem, To apply fix enter y on keybord. When fixing is complete reboot system and check filesystem again.

How to get SMNP information from router using PHP

First install SNMP package:

sudo apt-get install snmp

To use SNMP in PHP install php-snmp extention:

sudo apt-get install -y php-snmp

Get SNMP information from router user command:

snmpwalk -v2c -Cc -c public 192.168.1.1 > out.txt

This command will get all SNMP information from router 192.168.1.1 and save it into file out.txt

Now let’s create file index.php and write code that will get all MAC addresses from BDCOM P3310 OLT. To get all MAC addresses use OID: iso.3.6.1.2.1.17.7.1.2.2.1.1. In PHP file create function SnmpGet:

function SnmpGet($host, $community, $object_id){
    exec("snmpwalk  -v2c -Cc -c ".$community." ".$host." ".$object_id, $snmpWalkReturn);
    foreach($snmpWalkReturn as $value){
            $oid = explode("=", $value);
            $walk[trim($oid[0])] = trim($oid[1]);
    }
    return $walk;
}

Put SNMP result in variable $MacResult:

$MacResult = snmprealwalk2($hostname, $community, "iso.3.6.1.2.1.17.7.1.2.2.1.1");

In cycle foreach go through all elements and remove unnecessary data:

if(count($MacResult)){
    foreach($MacResult as $Item => $Value)
    {
        $Oid = str_replace("iso.3.6.1.2.1.17.7.1.2.2.1.1.", "", $Item);
        $Mac = str_replace("Hex-STRING: ", "", $Value);

        if(!strpos($Mac, "STRING:")){
            echo $Mac.' | '.$Oid;
        }
    }
}

Similarly get EPON interface id from OID: iso.3.6.1.2.1.17.7.1.2.2.1.2

How to install Arch Linux with i3

1 .Download Arch Linux ISO from official site: https://www.archlinux.org/download/

2. Create Live USB of Arch Linux using Etcher GUI tool:

Etcher GUI tool on Linux

Or You can use Rufus in Windows:

Once you have created a liveUSB for Arch Linux, restart your PC and boot from USB. While booting press Delete, F2, F10 or F12 key to go into boot menu.

3. Create partition.

Use the command fdisk to show and create partitions on your system:

fdisk -l

If you have old partitions on your disk, you can delete them all using command:

wipefs -a /dev/sda

Be careful! This command destroy all data on your hard drive.

Select the disk you are going to partition:

fdisk /dev/sda

Enter n – to create new partition, then program ask you to choose a disk number, enter 1, and then enter first and last block of dist (press Enter for default).

4. Create root partition. To format root partition use command:

mkfs.ext4 /dev/sda1

5. Install Arch Linux

mount /dev/sda1 /mnt

Use pacstrap script to install all necessary packages:

pacstrap /mnt base linux linux-firmware vim nano mc

Generate a fstab file to define how disk partition, block devices or remote file systems are mounted into the filesystem.

genfstab -U /mnt >> /mnt/etc/fstab

Use arch-chroot and set the mounted disk as root. Now Arch Linux is installed on the disk.

arch-chroot /mnt

6. Setting up timezone

timedatectl list-timezones
timedatectl set-timezone Europe/Kiev

7. Setting up Locale

locale-gen
echo LANG=en_US.UTF-8 > /etc/locale.conf
export LANG=en_US.UTF-8

8. Network configuration

echo name > /etc/hostname
touch /etc/hosts

How to create and compare md5 checksum of files

To create md5 checksum of all files in folder use command:

md5sum /etc/*

This comment will show all md5 checksum in /etc directory:

To write this checksum in text document use command:

md5sum /etc/* >> /file.txt

To compare checksum of files in folder with checksum of files in text document use command:

md5sum -c /file.txt

If checksums match, near the file will be record “Success”, it means that the file has not changed. Otherwise it means that the file was edited by someone.

To check your system, regularly create checksum files for directories: /etc, /bin, /sbin, / lib

Use md5sub recursive in sub-directories

If You want to create md5 checksum of all files in all sub-directories use next command, it will create md5 checksum of all files in /etc directory:

find -type f -exec md5sum '{}' \; > md5sum.txt

How To Set Up Apache Virtual Hosts on Ubuntu Linux

You will need to have Apache installed in order to work through these steps. If you haven’t already done so, you can get Apache installed on your server through apt-get:

sudo apt-get update
sudo apt-get install apache2

For example let’s create virtual Apache host test.host. Create host directory:

sudo mkdir -p /var/www/test.host/public_html

Now we have the directory structure for our files, but they are owned by our root user. If we want our regular user to be able to modify files in our web directories, we can change the ownership by doing this:

sudo chown -R $USER:$USER /var/www/test.host/public_html

We should also modify our permissions a little bit to ensure that read access is permitted to the general web directory and all of the files and folders it contains so that pages can be served correctly:

sudo chmod -R 755 /var/www

Virtual host files are the files that specify the actual configuration of our virtual hosts and dictate how the Apache web server will respond to various domain requests.

Apache comes with a default virtual host file called 000-default.conf that we can use as a jumping off point. We are going to copy it over to create a virtual host file for each of our domains.

We will start with one domain, configure it, copy it for our second domain, and then make the few further adjustments needed. The default Ubuntu configuration requires that each virtual host file end in .conf. Start by copying the file for the first domain:

sudo cp /etc/apache2/sites-available/000-default.conf /etc/apache2/sites-available/test.host.conf

Open the new file in your editor with root privileges:

sudo nano /etc/apache2/sites-available/test.host.conf

Change this file look something like this:

<VirtualHost *:80>
    ServerAdmin [email protected]
    ServerName test.host
    ServerAlias www.test.host
    DocumentRoot /var/www/test.host/public_html

    <Directory /var/www/test.host/public_html>
        Require all granted
    </Directory>

    ErrorLog ${APACHE_LOG_DIR}/error.log
    CustomLog ${APACHE_LOG_DIR}/access.log combined
</VirtualHost>

Now that we have created our virtual host files, we must enable them. Apache includes some tools that allow us to do this.

sudo a2ensite test.host.conf

Next, disable the default site defined in 000-default.conf:

sudo a2dissite 000-default.conf

When you are finished, you need to restart Apache to make these changes take effect:

sudo service apache2 restart

Connect to SSTP server from Linux

SSTP is Microsofts Remote Access Solution (RAS) for PPP over SSL. It can be used instead of PPTP or L2TP, and is only available with Windows Vista/7 connecting to a Windows 2008 Server. The advantage of SSTP compared to PPTP and L2TP is that it cannot be easily blocked by firewalls since the traffic is transmitted over HTTPS on port 443.

In Ubuntu Linux we can connect to SSTP by using SSTP-Client project on SourceForge.

To install SSTP-Client on Ubuntu add PPA repository:

sudo add-apt-repository ppa:eivnaes/network-manager-sstp

Then update package list and install packages sstp-client, network-manager-sstp by commands:

sudo apt update
sudo apt install sstp-client network-manager-sstp

Package network-manager-sstp is used only on Linux with graphic interface, on console Linux You don’t need to install this package.

To convert .CRT certificate to .PEM certificate use command:

openssl x509 -in mycert.crt -out mycert.pem -outform PEM

How to check SSD life in Linux

To check SSD Smart information install program: Smartmontools:

sudo apt-get intall smartmontools

To view information about SSD drive use command:

sudo smartctl -i /dev/sda

To view all Smart information about SSD use command:

sudo smartctl -a /dev/sda

To view only SSD health in percent use command:

sudo smartctl -a /dev/sda | grep Media_Wearout_Indicator

Install Nextcloud on Ubuntu server

To install Nextcloud on Ubuntu or other Linux use command:

sudo snap install nextcloud

After installation snap package check installation status

sudo snap changes nextcloud

To change default http and https ports use commands:

sudo snap set nextcloud ports.http=81
sudo snap set nextcloud ports.https=444

In Nginx proxy server configuration file change proxy_pass default port to 81:

Nextcloud’s automatic hostname detection can fail when behind a proxy; you might notice it redirecting incorrectly. If this happens, override the automatic detection (including the port if necessary), e.g.:

sudo nextcloud.occ config:system:set overwritehost --value="example.com:81"

Nextcloud and Nginx https proxy

If You use Nginx as https frontend and nextcloud as http backend – You neet co change /var/snap/nextcloud/20498/nextcloud/config.php insert the foloving lines:

  'overwrite.cli.url' => 'https://example.host',
  'overwriteprotocol' => 'https',

In Nginx http config file insert 301 redirect to https:

return 301 https://example.host$request_uri;

By default, PHP will use 128M as the memory limit. If you notice images not getting previews generated, or errors about memory exhaustion in your Nextcloud log, you may need to set this to a higher value.

If you’d like to set the memory limit to a higher value (say, 512M), run:

sudo snap set nextcloud php.memory-limit=512M

To set it to be unlimited (not recommended), use -1:

sudo snap set nextcloud php.memory-limit=-1

By default the cronjob interval is 15 minutes. To adjust it (say, 10 minutes) simply run:

sudo snap set nextcloud nextcloud.cron-interval=10m

Rescan all files for all users with occ console command:

sudo -u username php occ files:scan --all

Manjaro Linux – Install Apache, PHP, MariaDB – MySQL (LAMP)

To install “LAMP” – Apache, PHP, MySQL on Arch and Manjaro Linux do some steps:

First update Your operating system to latest version:

sudo pacman -Syyu

Apache

After updating Your system lets install Apache web server:

sudo pacman -S apache

Edit file /etc/httpd/conf/httpd.conf, search and comment the following line:
# LoadModule unique_id_module modules/mod_unique_id.so

sudo nano /etc/httpd/conf/httpd.conf

Enable Apache service and restart Apache service using commands:

sudo systemctl enable httpd
sudo systemctl restart httpd

Verify Apache status by command:

sudo systemctl status httpd

PHP

Now install latest version of PHP:

sudo pacman -S php php-apache

After installation we neet to configure out PHP.
Edit file: /etc/httpd/conf/httpd.conf

sudo nano /etc/httpd/conf/httpd.conf

Find the folowing line and comment it:

#LoadModule mpm_event_module modules/mod_mpm_event.so

Also uncomment or add the line:

LoadModule mpm_prefork_module modules/mod_mpm_prefork.so

Then add the following lines at the bottom of configuration file:

LoadModule php7_module modules/libphp7.so
AddHandler php7-script php
Include conf/extra/php7_module.conf

PHP installed. Now create index.php file in Apache home directory to check that PHP is installed correctly:

sudo nano /srv/http/index.php

<?php
phpinfo();
?>

Restart the PHP service:

sudo systemctl restart httpd

Go to http://127.0.0.1/ and check that Apache server with latest PHP version installed on your Manjaro Linux:

MySQL MariaDB

Install MySQL Server:

sudo pacman -S mysql

Initialize the MariaDB data directory prior to starting the service:

sudo mysql_install_db --user=mysql --basedir=/usr --datadir=/var/lib/mysql

Enable and srart MySQL service:

sudo systemctl enable mysqld 
sudo systemctl start mysqld

Check that MySQL service installed and work correctly:

sudo systemctl status mysqld

After installation MySQL You need to setup root user and password:

sudo mysql_secure_installation