If you dont want to login with password everytime or you want to use autossh then you should think about Key Login or Key based authentication in SSH.

Generate SSH-Key:

ssh-keygen

by default they are saved here

/home/pi/.ssh/

 

pi@pi:~/.ssh $ ls -lart
insgesamt 16
drwxr-xr-x 20 pi pi 4096 Jän 3 18:47 ..
-rw-r--r-- 1 pi pi 390 Jän 3 18:47 id_rsa.pub
-rw------- 1 pi pi 1679 Jän 3 18:47 id_rsa
drwx------ 2 pi pi 4096 Jän 3 18:47 .

show content of generated file:

more id_rsa.pub
ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDUs8HxOGrMjM72cf6vv952/qxZ3nOG+BJ9JRCF1JWX6c
JZiHQxce9gz/IZv02G5QL6KbPA5oy5bvNv7LFe25erFLle4rbixiCdKyQ3YjiJquz3R/9oMXYkF/HfJVE
GIYcSgXVF/oRBJbTiSZfG3ryiWgcqPu9zDNHtYHxLcwrzfffYIerDjR86TzXLux9Q+1WUz0MKV6nw5/
I/y9MF7dSo194J2H0qZhlbyf3QYZmC1b94YD7zAz6cayK3iIX1Q/Dra7OqD4v+jdkpkgpiyr1XoKodPo
RPQEYZHgKulwZpl71lqtOv+/oSyW+g+QomvbRXu9PqbXtbRThNQw4YfpiN pi@pi

Copy to remote machine (where you want to login without password)

vi /user/.ssh/authorized_keys

copy the content inside of this file.

SSH Connection to the host should now be possible without using password.

Makes also AutoSSH possible:

autossh -R 20000:localhost:22 root@domain.com

to connect from the other side:

ssh -p 20000 pi@localhost

Recieved 2 additional Raspis and couldnt’stop setting them up unfortunately the display ordered was broken so i didnt build the mobile RetroPi. So I tried it with my cheap china beamer:

   

Longrunner Cam with Raspberry and self build Lego Case.

 

Unfortunately broken display (Raspi HD TFT Hat 800×480).

But a 10″ touch screen and case arrived

Kuman Raspberry Pi 3.5

+ Raspberry Pi 3 B+

+ Anker PowerBar (10000 mAh)

Installed NetPi Image from: https://drive.google.com/drive/folders/1pCzC8NRPJU0gfBHewlNSo_Z0O3xk7fbY

see also:

http://www.blamethenetwork.com/netpiplus/

Install additional Kali-Tools

apt-get install git
# git clone https://github.com/LionSec/katoolin.git  && sudo cp katoolin/katoolin.py /usr/bin/katoolin
chmod +x /usr/bin/katoolin
katoolin

establish remote ssh-connection via ssh reverse tunnel (provides ssh-connection to rasp in a network via a server/device with a public ip)

on the raspberry:

ssh -R 2222:localhost:22 loginOfServerIP@ServerIP
on server side to connect back to raspberry:

ssh -p 2222 loginOfComputerWithoutPublicIP@localhost

verify usage of autossh  if regularely needed

mysql::db do failed: MySQL server has gone away at ./inclibdb.pm line 1848

Solved by

set a higher value for wait_timeout and connect_timeout in my.cnf

from the MySQL Documentation

  • wait_timeout : The number of seconds the server waits for activity on a noninteractive connection before closing it.
  • connect_timeout : The number of seconds that the mysqld server waits for a connect packet before responding with Bad handshake

EXAMPLES

  • If wait_timeout is 1800 (30 Minutes), the DB Connection will close in 30 minutes if the connection is idle (indicated by Sleep in the command column of the processlist).
  • If connect_timeout is 10, then mysqld will reject you if you cannot login (authenticate) in 10 seconds.

Kernel Panic after yum upgrade to kernel 3.10.0-957.1.3.el7.x86_64 ona Centos 7 VM:

– booted old kernel
– no initramfs-3.10.0-957.1.3.el7.x86_64.img in /boot

Solved by

– yum remove kernel-3.10.0-957.1.3.el7.x86_64

– verify uninstallation

rpm -qa | grep kernel | sort

– reinstall

yum install kernel-3.10.0-957.1.3.el7.x86_64

– verify again, check initramfs creation in /boot

rpm -qa | grep kernel | sort
ls -la /boot/initram

reboot into new kernel

see also: https://ma.ttias.be/reinstall-the-linux-kernel-on-centos-or-rhel/

Send mail via sendmail

vi /tmp/email.txt

Insert

Subject: Terminal Email Send
Email Content line 1
Email Content line 2

(ESC)wq(ENTER)

sendmail user@example.com < /tmp/email.txt

Quick and dirty, with subject only:

mail -s "Test Subject" user@example.com < /dev/null

Faking Mails with cutomized sender:

mail -s "Everything possible" -aFrom:bill.gargantur@iliketobeanemailfaker.com recipient@maildomain.com < /dev/null

*Will be delivered into spamfolder or not delivered cause SPF checks that mailsender is not authorized sender of the maildomain –> only if accurate spamsolution/SPF is implemented on recipient side

Install/Config sendmail
for just relay edit /etc/mail/sendmail.cf and add:

"Smart" relay host (may be null)

DSrelay.example.com

or if ip based:

"Smart" relay host (may be null)
DS[10.10.10.10]

of course relay host must permit this.

If you ever wanted an automation when a process is not running it is just a small script helping to achieve this:

check_process.sh (dont forget to make it executable)

check_process() {
  echo "$ts: checking $1"
  [ "$1" = "" ]  && return 0
  [ `pgrep -f $1` ] && return 1 || return 0 
#pgrep -n if process-name match exactly
}

while [ 1 ]; do
  # timestamp
  ts=`date +%T`
  echo "$ts: begin checking..."
  check_process "myprog.pl"
  [ $? -eq 0 ] && echo "$ts: not running, restarting..." && `/usr/bin/perl /home/me/myprog.pl >/dev/null`
sleep 10

done

You can also send yourself a mail instead of just starting process instead of

/usr/bin/perl /home/me/myprog.pl

do

echo "Subject: Process is stopped" | sendmail yourmail@mail.com

If you want to run this in background do

nohup check_process.sh &

or you can put this on startup via cronjob

crontab -e

@reboot root /home/me/check_process.sh

Origin/Source: https://stackoverflow.com/questions/7708715/check-if-program-is-running-with-bash-shell-script

Lack of free space? just type in

du -sk *|sort -n

on /

or any folder you like. You will get an information about space occupation where you can investigate further.

Sample output:

0 fastboot
0 proc
0 sys
4 boot
4 dev
4 lib64
4 media
4 mnt
4 srv
8 aquota.user
8 home
12 aquota.group
16 lost+found
120 tmp
644 run
6080 bin
7244 sbin
8544 etc
29076 lib
1345892 opt
1364796 usr
3028736 root
12280360 var