Create Centos 7 bootable USB from ISO file in Windows

This post shows you how to create bootable Centos 7 Installer USB from ISO file in Windows 10. You can also apply to Centos 6.8, 6.10 and Windows 7.

First of all download Centos 7 ISO file at:

http://isoredirect.centos.org/centos/

You can choose Centos 7 or Centos 6 depends on your need. In this post, I am using Centos 7 X86_64 1810 NetInstall for demo. But you can choose any other version of Centos in the same folder.

Next step is to download and install Universal USB Installer: Full guide here.

Start Universal USB Installer and select your downloaded ISO and USB driver as below:

Create bootable Centos 7 USB Driver from ISO
Create bootable Centos 7 USB Driver from ISO

Then wait the application to work.

P/S: select “Will Wipe Disk 1” tick will delete all data on USB.

That’s all. You’ve got a bootable Centos 7 Netinstall USB Drive to install on servers & pcs.

How to setup crontab on Ubuntu 18.04

This post guide you how to setup crontab on Ubuntu 18.04 but you can apply on different versions of Ubuntu.

First of all, edit crontab file at:

vi /etc/crontab

You will see something like this

#/etc/crontab: system-wide crontab
# Unlike any other crontab you don't have to run the `crontab'
# command to install the new version when you edit this file
# and files in /etc/cron.d. These files also have username fields,
# that none of the other crontabs do.
SHELL=/bin/sh
PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin
# m h dom mon dow user  command
17 *    * * *   root    cd / && run-parts --report /etc/cron.hourly
25 6    * * *   root    test -x /usr/sbin/anacron || ( cd / && run-parts --report /etc/cron.daily )
47 6    * * 7   root    test -x /usr/sbin/anacron || ( cd / && run-parts --report /etc/cron.weekly )
52 6    1 * *   root    test -x /usr/sbin/anacron || ( cd / && run-parts --report /etc/cron.monthly )

This is the default content of crontab file. Now you can add more schedules with syntax guide can be found at: Config9.com crontab guides

For example, to add a schedule runs at 1h 00 AM everyday under config9 username, you can add this line to that opened file:

0 1 * * * config9 /opt/app/app.sh

More templates, more guides will be at: Config9.com crontab guides.

After saving the file, we need to restart cron to schedules take effect:

# Check command
systemctl status cron

# restart command
systemctl restart cron

If you don’t have cron in your system, somehow, you will need to install cron with this command:

# Install cron if not available
sudo apt install -y cron

To check if cron is installed or not, using this command:

dpkg -l cron

Crontab run every weekends at 0:01 am

This post will guide you setup a crontab to run every weekends (Saturday & Sunday) at 0:01 am.

Cmd:10**0,6/cfg9/app.sh
minute(s)hour(s) in
24h format
day(s) of
month
month (s)weekdaysapplication path
Value0-590-231-311-12
1: Jan
2: Feb
3: Mar
4: Apr
5: May
6: Jun
7: Jul
8: Aug
9: Sep
10: Oct
11: Nov
12: Dec
0-6
0: Sunday
1: Monday
2: Tuesday
3: Wednesday
4: Thursday
5: Friday
6: Saturday

Final command: 1 0 * * 0,6 /cfg9/app.sh

Some special characters used in crontab

*Any value
,Value list separator
Range of values
/Step values

What is cron & crontab

cron is a time-based job scheduler in Unix-like computer operating systems. People who set up and maintain software environments use cron to schedule jobs (commands or shell scripts) to run periodically at fixed times, dates, or intervals.

crontab is a UNIX command that creates a table or list of commands, each of which is to be executed by the operating system at a specified time.

Basic crontab command guide

This is some basic crontab commands you’ll use a lot.

CommandMeaningNotes
crontab -eEdit your crontab file, or create one
if it doesn’t already exist.
crontab -lDisplay/List your crontab file
crontab -rRemove your crontab file
crontab -u usernameDisplay/Modify crontab file
belonging to a specific user if you are root

More detail on crontab command can be found with this command:

man crontab

Crontab run every weekends at 0:00 am

This post will guide you setup a crontab to run every weekends (Saturday & Sunday) at 0:00 am.

Cmd:00**0,6/cfg9/app.sh
minute(s)hour(s) in
24h format
day(s) of
month
month (s)weekdaysapplication path
Value0-590-231-311-12
1: Jan
2: Feb
3: Mar
4: Apr
5: May
6: Jun
7: Jul
8: Aug
9: Sep
10: Oct
11: Nov
12: Dec
0-6
0: Sunday
1: Monday
2: Tuesday
3: Wednesday
4: Thursday
5: Friday
6: Saturday

Final command: 0 0 * * 0,6 /cfg9/app.sh

Some special characters used in crontab

*Any value
,Value list separator
Range of values
/Step values

What is cron & crontab

cron is a time-based job scheduler in Unix-like computer operating systems. People who set up and maintain software environments use cron to schedule jobs (commands or shell scripts) to run periodically at fixed times, dates, or intervals.

crontab is a UNIX command that creates a table or list of commands, each of which is to be executed by the operating system at a specified time.

Basic crontab command guide

This is some basic crontab commands you’ll use a lot.

CommandMeaningNotes
crontab -eEdit your crontab file, or create one
if it doesn’t already exist.
crontab -lDisplay/List your crontab file
crontab -rRemove your crontab file
crontab -u usernameDisplay/Modify crontab file
belonging to a specific user if you are root

More detail on crontab command can be found with this command:

man crontab

Crontab run every weekends at 1 am

This post will guide you setup a crontab to run every weekends (Saturday & Sunday) at 1 am.

Cmd:*1**0,6/cfg9/app.sh
minute(s)hour(s) in
24h format
day(s) of
month
month (s)weekdaysapplication path
Value0-590-231-311-12
1: Jan
2: Feb
3: Mar
4: Apr
5: May
6: Jun
7: Jul
8: Aug
9: Sep
10: Oct
11: Nov
12: Dec
0-6
0: Sunday
1: Monday
2: Tuesday
3: Wednesday
4: Thursday
5: Friday
6: Saturday

Final command: * 1 * * 0,6 /cfg9/app.sh

Some special characters used in crontab

*Any value
,Value list separator
Range of values
/Step values

What is cron & crontab

cron is a time-based job scheduler in Unix-like computer operating systems. People who set up and maintain software environments use cron to schedule jobs (commands or shell scripts) to run periodically at fixed times, dates, or intervals.

crontab is a UNIX command that creates a table or list of commands, each of which is to be executed by the operating system at a specified time.

Basic crontab command guide

This is some basic crontab commands you’ll use a lot.

CommandMeaningNotes
crontab -eEdit your crontab file, or create one
if it doesn’t already exist.
crontab -lDisplay/List your crontab file
crontab -rRemove your crontab file
crontab -u usernameDisplay/Modify crontab file
belonging to a specific user if you are root

More detail on crontab command can be found with this command:

man crontab

Crontab run every day from Monday to Friday at 1 am

This post will guide you setup a crontab to run every day from Monday to Friday at 1 am.

Cmd:*1**1-5/cfg9/app.sh
minute(s)hour(s) in
24h format
day(s) of
month
month (s)weekdaysapplication path
Value0-590-231-311-12
1: Jan
2: Feb
3: Mar
4: Apr
5: May
6: Jun
7: Jul
8: Aug
9: Sep
10: Oct
11: Nov
12: Dec
0-6
0: Sunday
1: Monday
2: Tuesday
3: Wednesday
4: Thursday
5: Friday
6: Saturday

Final command: * 1 * * 1-5 /cfg9/app.sh

Some special characters used in crontab

*Any value
,Value list separator
Range of values
/Step values

What is cron & crontab

cron is a time-based job scheduler in Unix-like computer operating systems. People who set up and maintain software environments use cron to schedule jobs (commands or shell scripts) to run periodically at fixed times, dates, or intervals.

crontab is a UNIX command that creates a table or list of commands, each of which is to be executed by the operating system at a specified time.

Basic crontab command guide

This is some basic crontab commands you’ll use a lot.

CommandMeaningNotes
crontab -eEdit your crontab file, or create one
if it doesn’t already exist.
crontab -lDisplay/List your crontab file
crontab -rRemove your crontab file
crontab -u usernameDisplay/Modify crontab file
belonging to a specific user if you are root

More detail on crontab command can be found with this command:

man crontab

Crontab run every year at 1 am from 1st to 9th of all month from May to September

This post will guide you setup a crontab to run every year at 1 am from 1st to 9th of all month from May to September.

Cmd:*11-95-9*/cfg9/app.sh
minute(s)hour(s) in
24h format
day(s) of
month
month (s)weekdaysapplication path
Value0-590-231-311-12
1: Jan
2: Feb
3: Mar
4: Apr
5: May
6: Jun
7: Jul
8: Aug
9: Sep
10: Oct
11: Nov
12: Dec
0-6
0: Sunday
1: Monday
2: Tuesday
3: Wednesday
4: Thursday
5: Friday
6: Saturday

Final command: * 1 1-9 5-9 * /cfg9/app.sh

Some special characters used in crontab

*Any value
,Value list separator
Range of values
/Step values

What is cron & crontab

cron is a time-based job scheduler in Unix-like computer operating systems. People who set up and maintain software environments use cron to schedule jobs (commands or shell scripts) to run periodically at fixed times, dates, or intervals.

crontab is a UNIX command that creates a table or list of commands, each of which is to be executed by the operating system at a specified time.

Basic crontab command guide

This is some basic crontab commands you’ll use a lot.

CommandMeaningNotes
crontab -eEdit your crontab file, or create one
if it doesn’t already exist.
crontab -lDisplay/List your crontab file
crontab -rRemove your crontab file
crontab -u usernameDisplay/Modify crontab file
belonging to a specific user if you are root

More detail on crontab command can be found with this command:

man crontab

Crontab run every year at 1 am from 1st to 9th of May and June

This post will guide you setup a crontab to run every year at 1 am from 1st to 9th of May and Jun

Cmd:*11-95,6*/cfg9/app.sh
minute(s)hour(s) in
24h format
day(s) of
month
month (s)weekdaysapplication path
Value0-590-231-311-12
1: Jan
2: Feb
3: Mar
4: Apr
5: May
6: Jun
7: Jul
8: Aug
9: Sep
10: Oct
11: Nov
12: Dec
0-6
0: Sunday
1: Monday
2: Tuesday
3: Wednesday
4: Thursday
5: Friday
6: Saturday

Final command: * 1 1-9 5,6 * /cfg9/app.sh

Some special characters used in crontab

*Any value
,Value list separator
Range of values
/Step values

What is cron & crontab

cron is a time-based job scheduler in Unix-like computer operating systems. People who set up and maintain software environments use cron to schedule jobs (commands or shell scripts) to run periodically at fixed times, dates, or intervals.

crontab is a UNIX command that creates a table or list of commands, each of which is to be executed by the operating system at a specified time.

Basic crontab command guide

This is some basic crontab commands you’ll use a lot.

CommandMeaningNotes
crontab -eEdit your crontab file, or create one
if it doesn’t already exist.
crontab -lDisplay/List your crontab file
crontab -rRemove your crontab file
crontab -u usernameDisplay/Modify crontab file
belonging to a specific user if you are root

More detail on crontab command can be found with this command:

man crontab

Crontab run every year at 1 am on 1st and 9th of May and June

This post will guide you setup a crontab to run every year at 1 am on 1st and 9th of May and Jun

Cmd:*11,95,6*/cfg9/app.sh
minute(s)hour(s) in
24h format
day(s) of
month
month (s)weekdaysapplication path
Value0-590-231-311-12
1: Jan
2: Feb
3: Mar
4: Apr
5: May
6: Jun
7: Jul
8: Aug
9: Sep
10: Oct
11: Nov
12: Dec
0-6
0: Sunday
1: Monday
2: Tuesday
3: Wednesday
4: Thursday
5: Friday
6: Saturday

Final command: * 1 1,9 5,6 * /cfg9/app.sh

Some special characters used in crontab

*Any value
,Value list separator
Range of values
/Step values

What is cron & crontab

cron is a time-based job scheduler in Unix-like computer operating systems. People who set up and maintain software environments use cron to schedule jobs (commands or shell scripts) to run periodically at fixed times, dates, or intervals.

crontab is a UNIX command that creates a table or list of commands, each of which is to be executed by the operating system at a specified time.

Basic crontab command guide

This is some basic crontab commands you’ll use a lot.

CommandMeaningNotes
crontab -eEdit your crontab file, or create one
if it doesn’t already exist.
crontab -lDisplay/List your crontab file
crontab -rRemove your crontab file
crontab -u usernameDisplay/Modify crontab file
belonging to a specific user if you are root

More detail on crontab command can be found with this command:

man crontab

Crontab run every year at 1 am on 1st of May and June

This post will guide you setup a crontab to run every year at 1 am on 1st of May and Jun

Cmd:*115,6*/cfg9/app.sh
minute(s)hour(s) in
24h format
day(s) of
month
month (s)weekdaysapplication path
Value0-590-231-311-12
1: Jan
2: Feb
3: Mar
4: Apr
5: May
6: Jun
7: Jul
8: Aug
9: Sep
10: Oct
11: Nov
12: Dec
0-6
0: Sunday
1: Monday
2: Tuesday
3: Wednesday
4: Thursday
5: Friday
6: Saturday

Final command: * 1 1 5,6 * /cfg9/app.sh

Some special characters used in crontab

*Any value
,Value list separator
Range of values
/Step values

What is cron & crontab

cron is a time-based job scheduler in Unix-like computer operating systems. People who set up and maintain software environments use cron to schedule jobs (commands or shell scripts) to run periodically at fixed times, dates, or intervals.

crontab is a UNIX command that creates a table or list of commands, each of which is to be executed by the operating system at a specified time.

Basic crontab command guide

This is some basic crontab commands you’ll use a lot.

CommandMeaningNotes
crontab -eEdit your crontab file, or create one
if it doesn’t already exist.
crontab -lDisplay/List your crontab file
crontab -rRemove your crontab file
crontab -u usernameDisplay/Modify crontab file
belonging to a specific user if you are root

More detail on crontab command can be found with this command:

man crontab