Case 1. To check whether port 80 is opened on server1 and monitored by some app there:
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telnet server1 80 |
Case2. If no app listens the port on server, we need to start some monitoring tool first and then try telnet:
Start listening on server:
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ls | nc -l -p 80 |
Try to connect from client:
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telnet server1 80 |
Ssh connection to the server gives the warning below:
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Warning: the ECDSA host key for 'hdp1003' differs from the key for the IP address '192.168.1.105' |
Fix: remove entry for this IP
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ssh-keygen -R 192.168.1.105 |
or for specific user
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ssh-keygen -f "/root/.ssh/known_hosts" -R 192.168.1.105 |
All operations from sudo user sudo su
/etc/hostname
/etc/hosts
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sudo hostname mynewname sudo systemctl restart systemd-logind.service hostnamectl set-hostname mynewname |
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sudo rm /etc/ssh/ssh_host_* sudo dpkg-reconfigure openssh-server |
After reboot machine should be accessed by new name
Attempted to install forecast package in R 3.2 version, on Ubuntu 16.04 LTS Xenial Xerus:
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install.packages("forecast") |
but when installing dependent packages tseries, quadprod, RcppArmadillo, it produced an error:
/usr/bin/ld: cannot find -lblas, cannot find -llalapack
Solution: install these libs in linux terminal:
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sudo apt install libblas-dev liblapack-dev |
and install.packages("forecast") will work in R console
This helped me to resolve java.lang.ClassNotFoundException. Bash command scans jar files in the folder and prints who contains given class.
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1 |
find . -name '*.jar' -print0 | xargs -0 -I '{}' sh -c 'jar tf {} | grep Hello.class && echo {}' |
I always, always forget this command. I search it in internet again and again, every time when I need to determine my Linux version. I am going to stop it now – I memorize the command in my notes:
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1 |
lsb_release -a |
The lsb_release command provides certain LSB (Linux Standard Base) and
distribution-specific information. The key -a means all possible info, it is not much.
Ubuntu 16.04 Network Manager contains only one option for VPN, this is PPTP. Today I had to set up SSTP VPN connection to a corporate Windows network.
Import keys for SSTP: Continue reading
Short tips how to install and use Docker on Ubuntu Server 16.04
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sudo apt-get update sudo apt-key adv --keyserver hkp://p80.pool.sks-keyservers.net:80 --recv-keys 58118E89F3A912897C070ADBF76221572C52609D sudo apt-add-repository 'deb https://apt.dockerproject.org/repo ubuntu-xenial main' sudo apt-get update sudo apt-get install docker-engine |
How to configure server and client for SSH authentication without password.
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ssh-keygen -t rsa -b 2048 -v |
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$ ssh-copy-id -i dmitry.pub user1@myserver1 |
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Host * StrictHostKeyChecking no UserKnownHostsFile=/dev/null |
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#PermitRootLogin without-password PermitRootLogin yes |
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service ssh restart |
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%sudo ALL=(ALL:ALL) NOPASSWD:ALL |
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ssh user1@myserver1 |
Simple script to install latest Scala. It is 2.12.1 at the moment
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# Install Scala wget www.scala-lang.org/files/archive/scala-2.12.1.deb sudo dpkg -i scala-2.12.1.deb |
