Master Linux Boot Startup: Systemd, chkconfig, and Crontab Techniques

1. System Service

If a component is installed as a system service, its unit file (e.g., xxx.service) resides in /usr/lib/systemd/system. You can enable boot start using either systemctl or chkconfig.

systemctl method

systemctl enable xxx   # enable boot start
systemctl disable xxx  # cancel boot start
systemctl status xxx.service   # check status
systemctl list-unit-files --state=enabled   # list enabled units
systemctl list-unit-files --state=disabled  # list disabled units

Enabling creates a symlink under /etc/systemd/system/ (or /etc/systemd/user/) pointing to the unit file.

chkconfig method (more complex)

chkconfig --add xxx && chkconfig --level 3 xxx on   # add and enable at runlevel 3
chkconfig --list xxx   # view status (only SysV services)

To disable, either systemctl disable xxx or remove the corresponding symlink.

2. General Startup Scripts

When a component is not a system service, you can start it at boot by adding executable scripts.

Method 1: Append the command to /etc/rc.local (or its symlink /etc/rc.d/rc.local).

Method 2: Place a .sh script in /etc/profile.d.

Method 3: Write a script and append its execution line to /etc/rc.local.

Remember to make scripts executable with chmod +x.

3. Crontab Method

Crontab supports special keywords prefixed with @ to schedule tasks without the traditional five‑field time format.

@reboot   : run once after reboot
@yearly   : run once a year (0 0 1 1 *)
@monthly  : run once a month (0 0 1 * *)
@weekly   : run once a week (0 0 * * 0)
@daily    : run once a day (0 0 * * *)
@hourly   : run once an hour (0 * * * *)

Example to start a script at boot:

# crontab -e
@reboot /usr/local/daemonProcess/somescript.sh

4. Production Recommendations

In production, adopt a single boot‑start mechanism for all components to simplify operations and reduce error risk.

5. Appendix: Sample Startup Script

# chmod +x /etc/rc.d/rc.local
# /usr/local/AutoStartOnBoot.sh
chmod +x /usr/local/AutoStartOnBoot.sh
source /etc/profile
# redis
/usr/local/redis/redis-5.0.13/bin/redis-server /usr/local/redis/redis-5.0.13/conf/redis.conf
# zookeeper
rm -f /data/zookeeper/data/zookeeper_server.pid
/usr/local/apache-zookeeper-3.6.3-bin/bin/zkServer.sh start
# kafka
JMX_PORT=9999 /usr/local/kafka_2.13-2.7.1/bin/kafka-server-start.sh -daemon /usr/local/kafka_2.13-2.7.1/config/server.properties
# kafka-manager
rm -f /usr/local/kafka-manager-2.0.0.2/RUNNING_PID
nohup /usr/local/kafka-manager-2.0.0.2/bin/kafka-manager -Dconfig.file=/usr/local/kafka-manager-2.0.0.2/conf/application.conf -Dhttp.port=9002 >/dev/null 2>&1 &
# mysql
service mysqld start