How to add PHP support for jailed SSH users in ISPConfig 3

Jailkit is an easy to use tool to create and maintain jail environments for shell users on Linux. In this guide, I will show you how to move PHP and its dependencies into the jail so that the jailed user can execute PHP scripts inside the jail.
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How to Backup OpenVZ Containers with vzdump on CentOS 6

OpenVZ is a Linux based Kernel virtualization technology developed by SWSoft for its commercial product Virtuozzo. The modified Linux Kernel and the system utilities are released under an OpenSource license. Vzdump is a shell based backup program for OpenVZ virtual machines. It is made for containers that use the traditional "simfs" filesystem, it can not be used for containers with "ploop" filesystem.

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How to use IPTables on CentOS 7

Centos 7 replaced the traditional IPTables Linux Kernel Firewall with the Firewalld service. There are still a lot of scripts available that require the use of IPTables. A common example is the software Fail2ban.

In this guide, I will explain the installation of IPTables on Centos 7.x

The first step is to stop and mask the firewalld service:

systemctl stop firewalld
systemctl mask firewalld

Then install the "iptables-services" package with the yum package installer:

yum install iptables-services

And enable the new service:

systemctl enable iptables

IPTables is now ready to be used on your server. For example you can block an external IP address now with the iptables command:

iptables -A INPUT -s 192.168.0.10 -j DROP

Rules that you set with iptables persist only until the next reboot. To save them permanently use the following command:

service iptables save

How to list installed packages on Debian?

To get a list of all installed packages on a Debian or Ubuntu server, run the command:

dpkg --get-selections

This command will show you a rather long list. To save the list to a file, use this command:

dpkg --get-selections > /tmp/packages.txt

the list is saved then in the file /tmp/packages.txt.

If you seek for a specific package, use the grep command:

dpkg --get-selections | grep nginx

will show you all packages that contain the word "Nginx" in their name.

Example:

root@sv1:/# dpkg --get-selections | grep nginx
nginx-common                                    install
nginx-extras                                    install

How to change the Hostname on CentOS 7

The easiest way to change the hostname on CentOS 7 is to use the hostnamectl command.

First I will check the current hostname by running "hostnamectl status" on the shell of my server:

hostnamectl status

The output on my system is:

[root@server1 ~]# hostnamectl status
   Static hostname: server1.example.com
         Icon name: computer-vm
           Chassis: vm
        Machine ID: d89865d34b5a4637a9a4ff0ce0f6da02
           Boot ID: 56d1685056d743b39e57a7b9cbfe467c
    Virtualization: vmware
  Operating System: CentOS Linux 7 (Core)
       CPE OS Name: cpe:/o:centos:centos:7
            Kernel: Linux 3.10.0-123.el7.x86_64
      Architecture: x86_64

Then I change the hostname with the set-hostname option of the hostnamectl command to server2.example.com

hostnamectl set-hostname server2.example.com

Afterward, I check with the command hostname and hostname -f if the hostname change has succeeded.

hostname
hostname -f

The result should be:

[root@server1 ~]# hostname
server2.example.com
[root@server1 ~]# hostname -f
server2.example.com

Instead of the hostname command you could also use the "hostnamectl status" command again to check if the new hostname has been set:

[root@server1 ~]# hostnamectl status
   Static hostname: server2.example.com
         Icon name: computer-vm
           Chassis: vm
        Machine ID: d89865d34b5a4637a9a4ff0ce0f6da02
           Boot ID: 56d1685056d743b39e57a7b9cbfe467c
    Virtualization: vmware
  Operating System: CentOS Linux 7 (Core)
       CPE OS Name: cpe:/o:centos:centos:7
            Kernel: Linux 3.10.0-123.el7.x86_64
      Architecture: x86_64

How To Check And Repair All MySQL Databases on Debian And Ubuntu Linux

The Following command can be used to check and repair all MySQL databases on a Ubuntu or Debian Linux System.

Ubuntu Linux

sudo mysqlcheck --defaults-file=/etc/mysql/debian.cnf --auto-repair --optimize --all-databases

Debian Linux

mysqlcheck --defaults-file=/etc/mysql/debian.cnf --auto-repair --optimize --all-databases

The benefit of the above command is that it uses the debian-sys-maint login to MySQL which is available on every Debian and Ubuntu System, so you don't have to provide the MySQL root login details.

How to Copy Files with SCP between Linux Servers

1.1 SCP Command Line-An Overview

 

The SCP command line is commonly used to copy files over SSH, and between popular Operating systems like Linux, Mac and Windows in a secure fashion. SCP is used to copy files to/from a remote server. It also allows you to copy files from one remote server to another remote server, without passing traffic through your PC.

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Solution for: fatal: open database /var/lib/postfix/smtpd_scache.db: File exists

If your mail server stops working (neither incoming nor outgoing email works) and you find the following error message in the mail.log file:

fatal: open database /var/lib/postfix/smtpd_scache.db: File exists

then the smtpd_scache.db might got corrupted. Postfix will recreate this file if it does not exist. So it can be removed to solve the issue:

/etc/init.d/postfix stop
rm -f /var/lib/postfix/smtpd_scache.db
/etc/init.d/postfix start

Thanks to Alexander Fox for sending me this FAQ.