Whenever I restart my system MongoDB server fails to start.

     Loaded: loaded (/lib/systemd/system/mongod.service; enabled; vendor preset: enabled)
     Active: failed (Result: exit-code) since Sat 2021-07-03 14:24:44 IST; 15min ago
       Docs: https://docs.mongodb.org/manual
    Process: 14963 ExecStart=/usr/bin/mongod --config /etc/mongod.conf (code=exited, status=1/FAILURE)
   Main PID: 14963 (code=exited, status=1/FAILURE)

The only solution for this is to run

sudo mongod --fork --logpath /var/lib/mongodb/mongodb.log --dbpath /var/lib/mongodb

after the system restart.

But it gets annoying to start MongoDB every time on system restart.
Is there any other solution to this problem?

Yes there is a file /usr/bin/mongod

and content of configuration file

# mongod.conf

# for documentation of all options, see:
#   http://docs.mongodb.org/manual/reference/configuration-options/

# Where and how to store data.
storage:
  dbPath: /var/lib/mongodb
  journal:
    enabled: true
#  engine:
#  mmapv1:
#  wiredTiger:

# where to write logging data.
systemLog:
  destination: file
  logAppend: true
  path: /var/log/mongodb/mongod.log

# network interfaces
net:
  port: 27017
  bindIp: 127.0.0.1


# how the process runs
processManagement:
  timeZoneInfo: /usr/share/zoneinfo

#security:

#operationProfiling:

#replication:

#sharding:

## Enterprise-Only Options:

#auditLog:

#snmp:

also mongod.service

[Unit]
Description=MongoDB Database Server
Documentation=https://docs.mongodb.org/manual
After=network-online.target
Wants=network-online.target

[Service]
User=mongodb
Group=mongodb
EnvironmentFile=-/etc/default/mongod
ExecStart=/usr/bin/mongod --config /etc/mongod.conf
PIDFile=/var/run/mongodb/mongod.pid
# file size
LimitFSIZE=infinity
# cpu time
LimitCPU=infinity
# virtual memory size
LimitAS=infinity
# open files
LimitNOFILE=64000
# processes/threads
LimitNPROC=64000
# locked memory
LimitMEMLOCK=infinity
# total threads (user+kernel)
TasksMax=infinity
TasksAccounting=false

# Recommended limits for mongod as specified in
# https://docs.mongodb.com/manual/reference/ulimit/#recommended-ulimit-settings

[Install]
WantedBy=multi-user.target

Ok, corrected the log path to path: /var/lib/mongodb/mongodb.log in the configuration file, but the server still failed after a restart

Ok, changed the ownership of the /var/lib/mongodb, and everything works.

One question, I installed MongoDB server following the documentation for installation in ubuntu and never edited configuration files or others. So does it mean there is something wrong in the installation guide?