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Showing posts from June, 2016

Passwordless login with SSH Keygen

  What is a rsa key? RSA keys are a public key encryption method that keeps a private key on the host computer, and a public key on other machines. The public key is generated by a mathematical algorithm that can only be de-crypted with the private key. As long as the private key is kept confidential use of the keys is secure. Why use rsa keys? rsa keys are secure The keys are secure because they can be encrypted on a users computer protecting the key from falling into the wrong hands, unlike a password printed on a sticky note and place on your desk. The rsa key is also secure because it allows a server administrator to shut off password authentication on remote servers making a brute force attack that utilizes password dictionaries impossible. By default the rsa key is 2048 bits but this can be altered with the -b option. rsa keys are convenient Keys are easy to create, and distribute. The key allows near instant authentication without stopping to type a password every time you need

Filesystem and Directory size

  Just a quick look at df and du. This comes up a lot when we have filesystems that are filling up and need to find out which directories or logs are using the space. How to find the size of mounted filesystems From the terminal enter the df command. luke@testserver:~$ df -h Filesystem Size Used Avail Use% Mounted on udev 492M 12K 492M 1% /dev tmpfs 100M 780K 99M 1% /run /dev/xvda1 15G 3.1G 11G 22% / none 4.0K 0 4.0K 0% /sys/fs/cgroup none 5.0M 0 5.0M 0% /run/lock none 497M 0 497M 0% /run/shm none 100M 0 100M 0% /run/user According to its man page df “displays the amount of disk space available on the file system” adding the -h argument tells df to display in human readable format. Adding a “-T” notice caps will tell df to also display the filesystem type. luke@testserver:~$ df -hT Filesystem Type Size Used Avail Use% Mounted on udev devtmpfs 492M