Just Daily Notes
echo -n "Some string..."
echo -e "Some string...\c"
printf "a line without trailing linefeed"
printf "a line with trailing linefeed\n"
References
https://stackoverflow.com/questions/11193466/echo-without-newline-in-a-shell-script
systemctl is-active application.service
systemctl is-enabled application.service
systemctl is-active --quiet service
will exit with status zero if service is active, non-zero otherwise, making it ideal for scripts:
systemctl is-active --quiet service && echo Service is running
References
https://www.digitalocean.com/community/tutorials/how-to-use-systemctl-to-manage-systemd-services-and-units
https://unix.stackexchange.com/questions/396630/the-proper-way-to-test-if-a-service-is-running-in-a-script
You can use the chdir flag for Gunicorn to change to the project directory before executing your command.
gunicorn -w 2 -b 0.0.0.0:8000 --chdir /home/telessaude/telessaude_branch_master telessaude.wsgi_dev:application --reload --timeout 900
Check if File Exist
FILE=/etc/resolv.conf
if test -f "$FILE"; then
echo "$FILE exist"
fi
FILE=/etc/resolv.conf
if [ -f "$FILE" ]; then
echo "$FILE exist"
fi
FILE=/etc/resolv.conf
if [[ -f "$FILE" ]]; then
echo "$FILE exist"
fi
Check if Directory Exist
FILE=/etc/docker
if [ -d "$FILE" ]; then
echo "$FILE is a directory"
fi
Check if File does Not Exist
FILE=/etc/docker
if [ ! -f "$FILE" ]; then
echo "$FILE does not exist"
fi
Check if Multiple Files Exist
FILE=/etc/docker
if [ -f /etc/resolv.conf -a -f /etc/hosts ]; then
echo "$FILE is a directory"
fi
FILE=/etc/docker
if [ -f /etc/resolv.conf && -f /etc/hosts ]; then
echo "$FILE is a directory"
fi
File test operators
-f FILE – True if the FILE exists and is a regular file (not a directory or device).-G FILE – True if the FILE exists and has the same group as the user running the command.-h FILE – True if the FILE exists and is a symbolic link.-g FILE – True if the FILE exists and has set-group-id (sgid) flag set.-k FILE – True if the FILE exists and has a sticky bit flag set.-L FILE – True if the FILE exists and is a symbolic link.-O FILE – True if the FILE exists and is owned by the user running the command.-p FILE – True if the FILE exists and is a pipe.-r FILE – True if the FILE exists and is readable.-S FILE – True if the FILE exists and is socket.-s FILE – True if the FILE exists and has nonzero size.-u FILE – True if the exists and set-user-id (suid) flag is set.-w FILE – True if the FILE exists and is writable.-x FILE – True if the FILE exists and is executable.References
https://linuxize.com/post/bash-check-if-file-exists/
Environment directive
Environment="ONE=one" 'TWO=two two'
ExecStart=/bin/echo $ONE $TWO ${TWO}
EnvironmentFile directive
EnvironmentFile similar to Environment directive but reads the environment variables from a text file. The text file should contain new-line-separated variable assignments.This environment file can then be sourced and its variables used
Example file : /run/metadata/coreos
COREOS_DIGITALOCEAN_IPV4_ANCHOR_0=X.X.X.X COREOS_DIGITALOCEAN_IPV4_PRIVATE_0=X.X.X.X COREOS_DIGITALOCEAN_HOSTNAME=test.example.com COREOS_DIGITALOCEAN_IPV4_PUBLIC_0=X.X.X.X COREOS_DIGITALOCEAN_IPV6_PUBLIC_0=X:X:X:X:X:X:X:X
[Unit]
Requires=coreos-metadata.service
After=coreos-metadata.service
[Service]
EnvironmentFile=/run/metadata/coreos
ExecStart=
ExecStart=/usr/bin/etcd2 \
--advertise-client-urls=http://${COREOS_DIGITALOCEAN_IPV4_PUBLIC_0}:2379 \
--initial-advertise-peer-urls=http://${COREOS_DIGITALOCEAN_IPV4_PRIVATE_0}:2380 \
--listen-client-urls=http://0.0.0.0:2379 \
--listen-peer-urls=http://${COREOS_DIGITALOCEAN_IPV4_PRIVATE_0}:2380 \
--initial-cluster=%m=http://${COREOS_DIGITALOCEAN_IPV4_PRIVATE_0}:2380
References
https://stackoverflow.com/questions/37864999/referencing-other-environment-variables-in-systemd
https://coreos.com/os/docs/latest/using-environment-variables-in-systemd-units.html
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 shadowsocks-libev-server@cloud.service --now sudo systemctl enable shadowsocks-libev-server@tifa.service --now
The status of shadowsocks-libev instances could be checked with the following commands:
sudo systemctl status shadowsocks-libev-server@cloud.service sudo systemctl status shadowsocks-libev-server@tifa.service
You can start shadowsocks-libev instances with the following commands:
sudo systemctl start shadowsocks-libev-server@cloud.service sudo systemctl start shadowsocks-libev-server@tifa.service
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