Adding environment variables and templates to systemctl service

systemd.exec Chinese Manual ：http://www.jinbuguo.com/systemd/systemd.exec.html#%E7%8E%AF%E5%A2%83%E5%8F%98%E9%87%8F

environment variable （ Reference the above connection ）

Environment=

Set the environment variables of the process , Accept a space delimited VAR=VALUE list . You can use this option multiple times to add new variables or modify existing variables ( The same variable is subject to the last setting ). Set to blank to clear all previously set variables . Be careful ： (1) There is no variable expansion inside the string ( That is to say "$“ No special meaning ); (2) If the value contains spaces or equal signs , You must use double quotation marks around the string (”) Definition .

for example ：

Environment=“VAR1=word1 word2” VAR2=word3 “VAR3=$word56"set\; upSet\; up了"VAR1","VAR2","VAR3"3、\; ...\; andindividualchangeThe\; amount,Itsvaluebranchotherby"word1word2","word3","$word 5 6”

Be careful , Do not use environment variables to pass confidential information to processes in the unit ( Such as passwords and passwords ). One side , Environment variables will pass D-Bus IPC Exposed to other non privileged clients ; On the other hand , Environment variables are not classified as confidential data that need to be protected in concept . Besides , Because environment variables can propagate along the process tree , And be able to cross safe boundaries ( for example setuid/setgid Program ), Therefore, confidential data may be leaked to processes that should not be accessed .

EnvironmentFile=

And Environment= similar , The difference is that this option reads the settings of environment variables from a text file . Blank lines and semicolons in the file (;) Or well number (#) The first row is ignored , The format of other lines must conform to VAR=VALUE Of shell Variable assignment syntax . Backslash at the end of the line () Will be treated as a continuation character , This is related to shell Grammatical similarity . If you want to include spaces in variable values , You must use double quotation marks at both ends of the value (") Definition .

The file must be represented by an absolute path ( You can include wildcards ). But you can add... Before the path “-” Prefix means to ignore nonexistent files . You can use this option multiple times , To read settings from multiple different files . If set to null , Means empty All environment variables that have been previously read from the file .

The files listed here will be read immediately before the process starts , Therefore, the configuration file can be generated from the previous cell , The next unit reads it .

The environment variables read from the file will overwrite Environment= Variable with the same name set in . The order in which files are read is the order in which they appear in the unit file , And for the same variable , The settings in the last read file shall prevail .

PassEnvironment=

Certain certain systemd System service manager process (PID=1) The environment variables held are passed to the processes in the unit . Accept a space separated list of variable names . You can use this option multiple times to pass more variables . If set to null , It means that all variables that have been set previously are cleared . If the variable set here is not the system service manager process (PID=1) Environment variables held , Then it will be quietly ignored . Be careful , This option is only available for passing PID=1 Of systemd Environment variables held by the system service manager process , Because the system service unit does not automatically inherit by default PID=1 Environment variables held by the process . And because the user service unit will automatically inherit by default PID≠1 Of systemd All environment variables of the user service manager process , So this option has no meaning for user service manager .

Be careful , The value of the environment variable passed through this option will be Environment= or EnvironmentFile= The variable with the same name in the option .

for example ：

PassEnvironment=VAR1 VAR2 VAR3
Pass the “VAR1”, “VAR2”, “VAR3” Three variables , Its value is equal to PID=1 The value held by the process .

See environ(7) To learn more about the details of environment variables .

UnsetEnvironment=

Explicitly undo the specific environment variables of the unit . Accept a space separated variable name (“NAME”) With specific value variables (“NAME=VALUE”) list . You can use this option multiple times to undo more variables . If set to null , Then it means that all the previously set lists are cleared . Specific value variable (“NAME=VALUE”) Means only if the variable "NAME" The value of is exactly equal to "VALUE" Will be revoked "NAME" Variable . Ordinary variable names (“NAME”) It means no matter the variable "NAME" What is the value of , Will be unconditionally revoked "NAME" Variable . Be careful , because UnsetEnvironment= The undo operation of takes place in the last step before passing the environment variable to the process in the cell , So this option can undo environment variables from various channels , Include ： (1) from Environment= or EnvironmentFile= Set environment variables ; (2) Environment variables inherited from the global settings of the service manager ( See systemd-system.conf(5) In the manual DefaultEnvironment= Options ); (3) according to PassEnvironment= Inherited environment variables ; (4) Environment variables set by the service manager ( for example $NOTIFY_SOCKET And so on ); (5) from PAM Environment variables set by the module ( If set PAMName= Words ).

systemctl +kylin Components demo

 vi /usr/lib/systemd/system/kylin.service

adopt EnvironmentFile=/opt/bdp/kylin/kylinEnv Call environment variables

[Unit]
#  The service description 
Description=cosmo-bdp kylin
After=network-online.target
Requires=network-online.target

[Service]
Type=forking
#  Start command 
ExecStart=/bin/bash -c "JAVA_HOME=/usr/local/java exec /opt/bdp/kylin/bin/kylin.sh start"
EnvironmentFile=/opt/bdp/kylin/kylinEnv
Restart=no
RestartSec=30
RemainAfterExit=yes

[Install]
WantedBy=multi-user.target

Edit the relevant environment variables of the file configuration

[[email protected] bdp]# cat /opt/bdp/kylin/kylinEnv
HADOOP_HOME=/opt/bdp/hdfs
HIVE_HOME=/opt/bdp/hive
SPARK_HOME=/opt/bdp/spark-3.1.2-bin-hadoop3.2
KYLIN_HOME=/opt/bdp/kylin
PATH=/opt/bdp/hive/bin:/opt/bdp/hdfs/sbin:/opt/bdp/hdfs/bin:/opt/bdp/spark-3.1.2-bin-hadoop3.2/bin:/opt/bdp/kylin/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/root/bin
[[email protected] bdp]#

systemctl daemon-reload
systenctl restart kylin