How to Backup OpenVZ Containers with vzdump on CentOS 6

OpenVZ is a Linux based Kernel virtualisation technology developed by SWSoft for its commercial product virtuozzo. The modified Linux Kernel and the system utilities are released under a 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.

Continue reading How to Backup OpenVZ Containers with vzdump on CentOS 6

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

wget command – how to limit the download rate

Sometimes it is nescessary to limit the download rate of the wget command, e.g. when you are downloading a large file over a slow internet connection. The parameter to apply a download speed limit is the --limit-rate option. This setting is followed by the rate limit plus "k" for kbit or "m" for mbit.

Example:

wget --limit-rate 128k http://downloadserver.tld/bigfile.zip

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 specificy 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 easiets 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

Afterwats 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 set a VNC password

The Linux VNC server provides a command to set a new password. The command is "vncpasswd", the password is stored in encrypted form into the file ~/.vnc/passwd of the home directory of te user. Run:

vncpasswd

to set a new password for the currently logged in user. The command will then prompt for the new password. If you like to set a new VNC password for a different user, then append the password file name to the command. Example for the user "jane":

vncpasswd /home/jane/.vnc/passwd

The above command to set a new password for jane requires it that you are logged in as root user. On Ubuntu systems you can use sudo instead:

sudo vncpasswd /home/jane/.vnc/passwd

Which ports are used on a ISPConfig 3 server and shall be open in the firewall?

Here is a list of ports that are used commonly on ISPConfig 3 servers. If you dont have all services installed or if you e.g. dont want to connect to MySQL from external servers, then close the unused or unwanted ports.

TCP ports

20 - FTP Data
21 - FTP Command
22 - SSH
25 - Email
53 - DNS
80 - HTTP (Webserver)
110 - POP3 (Email)
143 -Imap (Email)
443 - HTTPS (Secure webserver)
993 - IMAPS (Secure Imap)
995 - POP3S (Secure POP§)
3306 - MySQL Database server
8080 - ISPConfig web interface
8081- ISPConfig apps vhost

UDP ports

53 - DNS
3306 - MySQL