journalctl -u service-name.service
Or, to see only log messages for the current boot:
journalctl -u service-name.service -b
References
https://unix.stackexchange.com/questions/225401/how-to-see-full-log-from-systemctl-status-service
[Unit] Description=My Website After=syslog.target network.target mongodb.service
The important part is the mongodb.service
References
https://stackoverflow.com/questions/21830670/systemd-start-service-after-specific-service
java -Dname=monitoring_core -jar core.jar
Use the ps Command to Find Running Processes:
ps -e -o pid,comm,command | grep 'monitoring_core'
References
https://stackoverflow.com/questions/1057247/how-can-i-set-the-process-name-for-a-java-program
https://www.tecmint.com/find-process-name-pid-number-linux/
https://linuxhint.com/ps_command_linux/
For example, Cloud and Tifa, two AVALANCHE members, are planning to deploy shadowsocks-libev services on the same VPS to bypass the firewall of Shinra Inc. In this case, they could simply create cloud.json and tifa.json configurations with different ports, passwords and encryption methods in /etc/shadowsocks-libev directory. Then enable and start the systemd services using the following commands:
sudo systemctl enable [email protected] --now sudo systemctl enable [email protected] --now
The status of shadowsocks-libev instances could be checked with the following commands:
sudo systemctl status [email protected] sudo systemctl status [email protected]
You can start shadowsocks-libev instances with the following commands:
sudo systemctl start [email protected] sudo systemctl start [email protected]
References
https://blog.zzhou612.com/2019/02/15/configure-multiple-users-for-shadowsocks-libev/
The return value is stored in $?. 0 indicates success, others indicates error.
some_command
if [ $? -eq 0 ]; then
echo OK
else
echo FAIL
some_command
retval=$?
do_something $retval
if [ $retval -ne 0 ]; then
echo "Return code was not zero but $retval"
fi
References
https://askubuntu.com/questions/29370/how-to-check-if-a-command-succeeded
References
https://pypi.org/project/python-snap7/
https://python-snap7.readthedocs.io/en/latest/installation.html
https://simplyautomationized.blogspot.com/2014/12/raspberry-pi-getting-data-from-s7-1200.html
https://simplyautomationized.blogspot.com/2016/02/python-snap7-s7-1200-simple-example.html
https://simplyautomationized.blogspot.com/2016/02/raspberry-pi-python-snap7-data-blocks.html
sudo a2enmod proxy_http sudo a2enmod proxy_fcgi sudo a2enmod proxy_wstunnel
# VirtualHost ms.example.net
<VirtualHost *:80>
ServerName ms.example.net
ProxyRequests Off
ProxyPreserveHost On
RemoteIPHeader X-Forwarded-For
<Proxy *>
Order deny,allow
Allow from all
</Proxy>
RewriteEngine On
RewriteCond %{REQUEST_URI} ^/socket.io [NC]
RewriteCond %{QUERY_STRING} transport=websocket [NC]
RewriteRule /(.*) ws://localhost:14102/$1 [P,L]
ProxyPass /socket.io http://localhost:14102/socket.io
ProxyPassReverse /socket.io http://localhost:14102/socket.io
</VirtualHost>
<VirtualHost *:443>
ServerName ms.example.net
ProxyRequests Off
ProxyPreserveHost On
RemoteIPHeader X-Forwarded-For
RewriteEngine on
<Proxy *>
Order deny,allow
Allow from all
</Proxy>
SSLEngine On
SSLCertificateFile /etc/letsencrypt/live/example.net/fullchain.pem
SSLCertificateKeyFile /etc/letsencrypt/live/example.net/privkey.pem
RewriteEngine On
RewriteCond %{REQUEST_URI} ^/socket.io [NC]
RewriteCond %{QUERY_STRING} transport=websocket [NC]
RewriteRule /(.*) ws://localhost:14102/$1 [P,L]
ProxyPass /socket.io http://localhost:14102/socket.io
ProxyPassReverse /socket.io http://localhost:14102/socket.io
</VirtualHost>
Use a secure URL for your initial connection, i.e. instead of “http://” use “https://”. If the WebSocket transport is chosen, then Socket.IO should automatically use “wss://” (SSL) for the WebSocket connection too.
var socket = io.connect('https://localhost', {secure: true});
References
http://xpo6.com/socket-io-via-apache-reverse-proxy/
https://stackoverflow.com/questions/36472920/apache-proxy-configuration-for-socket-io-project-not-in-root
https://gist.github.com/iacchus/954e0787d6893c5ab8e1
https://stackoverflow.com/questions/6599470/node-js-socket-io-with-ssl
apt-get install software-properties-common add-apt-repository ppa:vbernat/haproxy-2.0
apt-get update apt-get install haproxy=2.0.\*
References
https://haproxy.debian.net/
Black 0;30 Dark Gray 1;30 Red 0;31 Light Red 1;31 Green 0;32 Light Green 1;32 Brown/Orange 0;33 Yellow 1;33 Blue 0;34 Light Blue 1;34 Purple 0;35 Light Purple 1;35 Cyan 0;36 Light Cyan 1;36 Light Gray 0;37 White 1;37
RED='\033[0;31m' NC='\033[0m' # No Color
echo -e "I ${RED}love${NC} Stack Overflow"
References
https://stackoverflow.com/questions/5947742/how-to-change-the-output-color-of-echo-in-linux
https://misc.flogisoft.com/bash/tip_colors_and_formatting
tput setaf 1; echo "this is red text"
The count of colors available to tput is given by tput colors
To see the basic 8 colors (as used by setf in urxvt terminal and setaf in xterm terminal):
Color #define Value RGB black COLOR_BLACK 0 0, 0, 0 red COLOR_RED 1 max,0,0 green COLOR_GREEN 2 0,max,0 yellow COLOR_YELLOW 3 max,max,0 blue COLOR_BLUE 4 0,0,max magenta COLOR_MAGENTA 5 max,0,max cyan COLOR_CYAN 6 0,max,max white COLOR_WHITE 7 max,max,max
To print all 256 colors in the terminal, try the following one-liner:
for c in {0..255}; do tput setaf $c; tput setaf $c | cat -v; echo =$c; done
References
https://stackoverflow.com/questions/5947742/how-to-change-the-output-color-of-echo-in-linux
https://unix.stackexchange.com/questions/269077/tput-setaf-color-table-how-to-determine-color-codes