Category: Administration / Server


the strangest thing about mtr is probably that it seems to work only with a desktop-terminal. not an ssh-terminal 😀 What is MTR? mtr combines the functionality of the ‚traceroute‘ and ‚ping‘ programs in a single network diagnostic tool. As […]


Init Ram Disk filesystem – kind of mini OS in order to mount raid and start „the real /root os“. hostnamectl; # tested on Static hostname: debian9 Icon name: computer-vm Chassis: vm Machine ID: 532eabca552b4075a8679094397c8dba Boot ID: 15ee0b8e8a1e4d1eb1003c4630644091 Virtualization: microsoft […]


you should setup harddisk encryption during setup. to add an encrypted /home partition afterwards might be possible but a lot more effort. scroll very down if you want to know how to encrypt an usb sticks … needless to say […]

gnu linux smart s.m.a.r.t harddisk faillure surveillance

harddisks… are blackboxes of data – if something fails… you do not repair – you replace. 65% of all harddisk failurs can be announced with smart. wohoo! so don’t rely on it 😀 apt-get install smartmontools # some commands smartctl […]


btrfs is used by SUSE12 for the /root partition – where it is doing daily snapshots of the installed OS. It has more functionality built-in than just storing files. This article wants to take btrfs for a test-drive. Video Tutorials: […]

GNU Linux -> undelete ext3 vs ext4

As we all know… if you accidentally deleted a file… you better have a working backup. If not: Try to do as less write access as possible to the disk – turn off PC and boot from Live-CD-USB-Stick such as […]


can be easily checked via: root@debian9:~# cat /proc/filesystems nodev sysfs nodev rootfs nodev ramfs nodev bdev nodev proc nodev cpuset nodev cgroup nodev cgroup2 nodev tmpfs nodev devtmpfs nodev debugfs nodev tracefs nodev securityfs nodev sockfs nodev bpf nodev pipefs […]


strace from the manpage. trace system calls and signals In the simplest case strace runs the specified command until it exits. It intercepts and records the system calls which are called by a process and the signals which are […]

centos redhat compiling the latest kernel

this also worked under debian9 stretch… it now also works for Centos7/Redhat. in this example i try to compile the latest kernel from on CentOS7 it compiles… and boots up… hit ESC or other keys to see the verbose […]

Linux Kernel – Security Updates

latest kernel related security problems can be found here… -> newsletter subsribe: also


to be honest… i find all of those meassurement tools too complicated to install. they probably all have their validity – but why not simply do it like this: given that you have a webserver installed and the web-root is […]

akamai state of the internet quarterly report
23.06.2017 security Q1 2017: connectivity: Q4 2016


per default debian is not configured to forward traffic. on server/router/gateway: ping; # make sure internet connection works ifconfig eth0:0 netmask up; # add additional ip vim /etc/sysctl.conf # Uncomment the next line to enable packet forwarding […]


with tcpdump you can monitor IP packages, UDP packages, ICMP (ping). zypper install tcpdump; # comes preinstalled in suse12 apt-get install tcpdump; # debian8 yum install tcpdump; # centos7 redhat tcpdump -i eth0 tcpdump -vnni eth0; # very verbose root@Debian8:~# […]


show the ARP cache every network interface card (NIC)/LAN network card has a unique-as-possible vendor-asigned MAC address in the format 00:15:5d:00:07:08 this address is changeable like this: ip link set dev eth0 down; ip link set dev eth0 address 00:15:5d:00:07:09; […]


simple but usefull – you have the ip address of an computer in your local LAN – but you don’t know it’s computername. for internet-usage the host command is usefull because it shows – if a website is reachable by […]

IPv4 CIDR Subnet Mask Notation

IPv4 CIDR Subnet Mask Notation The CIDR number comes from the number of 1’s in the subnet mask when converted to binary. The common subnet mask is 11111111.11111111.11111111.00000000 in binary. This adds up to 24 1’s, or /24 (pronounced […]

19.06.2017 (December 1998) Network Working Group, S. Deering (Cisco), R. Hinden (Nokia) larger address space (128 bits, compared with 32 bits in IPv4, allowing 2^128 = 340.282.366.920.938.463.463.374.607.431.770.000.000 devices(addresses) to be registered, while IPv4 allowed only 2^32 = 4.294.967.296 devices […]


IPv6: Goodbye to broadcast, say hello to Multicast » IPv6 while broadcast sends the traffic to all computers in the network – multicast follows a „subscribe to service“ model. broadcast -> a computer using ARP sends a packet to FF:FF:FF:FF:FF:FF […]