WEBVTT 1 00:00:00.260 --> 00:00:02.910 In this lesson, we will learn about Cron 2 00:00:02.910 --> 00:00:04.830 and Scheduled Tasks. 3 00:00:04.830 --> 00:00:08.130 Cron and Scheduled Tasks are tools used 4 00:00:08.130 --> 00:00:10.710 to automate the execution of scripts 5 00:00:10.710 --> 00:00:14.010 and commands at predefined times in Linux 6 00:00:14.010 --> 00:00:16.980 and Windows operating systems respectively. 7 00:00:16.980 --> 00:00:19.140 Cron is short for Chronos, 8 00:00:19.140 --> 00:00:20.820 the Greek word for time. 9 00:00:20.820 --> 00:00:24.540 The Cron application is a time-based job scheduler 10 00:00:24.540 --> 00:00:26.100 in Linux systems. 11 00:00:26.100 --> 00:00:30.030 Cron allows users to automate repetitive tasks 12 00:00:30.030 --> 00:00:34.560 like running security scans or updating system logs 13 00:00:34.560 --> 00:00:39.210 by specifying the exact time and frequency of execution. 14 00:00:39.210 --> 00:00:43.740 Scheduled tasks in Windows serve a similar purpose, 15 00:00:43.740 --> 00:00:46.440 enabling the automation of tasks 16 00:00:46.440 --> 00:00:48.720 such as running PowerShell scripts 17 00:00:48.720 --> 00:00:52.320 or performing system maintenance at scheduled intervals. 18 00:00:52.320 --> 00:00:55.680 Let's learn more about Cron and Scheduled Tasks 19 00:00:55.680 --> 00:00:58.560 then we'll conduct Cron demonstration. 20 00:00:58.560 --> 00:01:00.330 First we have Cron. 21 00:01:00.330 --> 00:01:04.860 Cron is a time-based job scheduler used in Linux systems 22 00:01:04.860 --> 00:01:08.970 to automate tasks by specifying the exact time 23 00:01:08.970 --> 00:01:11.220 and frequency of execution. 24 00:01:11.220 --> 00:01:12.810 It is particularly useful 25 00:01:12.810 --> 00:01:17.160 for automating repetitive tasks like running security scans 26 00:01:17.160 --> 00:01:21.000 or updating system logs at predefined intervals. 27 00:01:21.000 --> 00:01:24.690 Cron is controlled by a file called the crontab 28 00:01:24.690 --> 00:01:28.140 where users define tasks they want to schedule. 29 00:01:28.140 --> 00:01:32.370 Each line in the crontab file represents a task 30 00:01:32.370 --> 00:01:36.570 specifying the minute, hour, day of the month, month 31 00:01:36.570 --> 00:01:39.540 and day of the week when the task should run. 32 00:01:39.540 --> 00:01:41.700 Through scheduling and automation, 33 00:01:41.700 --> 00:01:44.820 Cron ensures that tasks are executed 34 00:01:44.820 --> 00:01:48.810 without manual intervention, making it an important tool 35 00:01:48.810 --> 00:01:52.050 for maintaining automated system operations. 36 00:01:52.050 --> 00:01:56.400 Specifically the crontab file follows a specific format 37 00:01:56.400 --> 00:01:59.220 to determine when tasks are executed. 38 00:01:59.220 --> 00:02:02.910 For example, a line in the crontab might read, 39 00:02:02.910 --> 00:02:07.910 20 20 * * 1-5 and then the name of the script, 40 00:02:09.140 --> 00:02:12.930 /scripts/backup-server. 41 00:02:12.930 --> 00:02:16.980 This would schedule a script to run every day defined 42 00:02:16.980 --> 00:02:20.760 as days one through five in the crontab format, 43 00:02:20.760 --> 00:02:25.710 and it would execute at 8:20 PM or the 20th hour 44 00:02:25.710 --> 00:02:27.210 and the 20th minute. 45 00:02:27.210 --> 00:02:30.690 The flexibility of crontab format allows users 46 00:02:30.690 --> 00:02:33.930 to define schedules down to the minute 47 00:02:33.930 --> 00:02:37.290 or for specific days of the week or month. 48 00:02:37.290 --> 00:02:40.260 This scheduling capability is crucial 49 00:02:40.260 --> 00:02:44.250 for security operations where tasks like integrity checks 50 00:02:44.250 --> 00:02:47.400 or log analysis need to occur regularly 51 00:02:47.400 --> 00:02:50.820 to ensure the system remains secure and stable. 52 00:02:50.820 --> 00:02:54.330 Finally, Cron can be integrated with bash scripts 53 00:02:54.330 --> 00:02:58.710 to perform various tasks such as a scanning log files, 54 00:02:58.710 --> 00:03:02.910 monitoring system activity, or checking file integrity. 55 00:03:02.910 --> 00:03:05.640 For instance, a script could be set up 56 00:03:05.640 --> 00:03:07.830 to compare the current hash values 57 00:03:07.830 --> 00:03:11.280 of files against the known good hashes 58 00:03:11.280 --> 00:03:14.340 to detect unauthorized modifications. 59 00:03:14.340 --> 00:03:16.830 If the values do not match, 60 00:03:16.830 --> 00:03:18.930 the script could trigger an alert, 61 00:03:18.930 --> 00:03:21.180 notifying system administrators 62 00:03:21.180 --> 00:03:23.910 of potential security breaches. 63 00:03:23.910 --> 00:03:27.840 This capability allows for continuous monitoring 64 00:03:27.840 --> 00:03:32.370 and automated responses to potential security threats, 65 00:03:32.370 --> 00:03:35.250 reducing the need for manual oversight. 66 00:03:35.250 --> 00:03:39.540 So overall, Cron is used in automating system maintenance 67 00:03:39.540 --> 00:03:43.020 and security operations on Linux systems. 68 00:03:43.020 --> 00:03:46.920 By scheduling tasks to run at specific intervals, 69 00:03:46.920 --> 00:03:49.110 administrators can ensure 70 00:03:49.110 --> 00:03:53.520 that important processes like system updates, backups, 71 00:03:53.520 --> 00:03:58.520 and scans are executed consistently and on time. 72 00:03:58.680 --> 00:04:02.550 This automation reduces the risk of human error 73 00:04:02.550 --> 00:04:05.490 and ensures that the system remains secure 74 00:04:05.490 --> 00:04:10.440 and well maintained without constant manual intervention. 75 00:04:10.440 --> 00:04:13.470 Second, we have Scheduled Tasks. 76 00:04:13.470 --> 00:04:17.340 Scheduled Tasks is a time-based job scheduler 77 00:04:17.340 --> 00:04:21.240 used in Windows systems to automate tasks 78 00:04:21.240 --> 00:04:26.220 by specifying the exact time and frequency of execution. 79 00:04:26.220 --> 00:04:27.870 It is particularly useful 80 00:04:27.870 --> 00:04:30.300 for automating repetitive tasks 81 00:04:30.300 --> 00:04:34.170 like running maintenance scripts, performing system backups, 82 00:04:34.170 --> 00:04:37.890 or deploying software updates at set intervals. 83 00:04:37.890 --> 00:04:39.660 Scheduled Tasks are managed 84 00:04:39.660 --> 00:04:41.850 through the Windows Task scheduler 85 00:04:41.850 --> 00:04:45.210 where users define and configure tasks. 86 00:04:45.210 --> 00:04:50.100 Each task can be set to run at a specific time on a daily, 87 00:04:50.100 --> 00:04:53.460 weekly, or monthly basis without the need 88 00:04:53.460 --> 00:04:55.320 for manual intervention. 89 00:04:55.320 --> 00:04:58.770 Scheduled tasks follow a straightforward process 90 00:04:58.770 --> 00:05:03.030 for setting up when and how tasks are executed. 91 00:05:03.030 --> 00:05:06.750 For instance, users can specify a task 92 00:05:06.750 --> 00:05:09.690 to run every day at a certain time 93 00:05:09.690 --> 00:05:13.650 or every week on a particular day. 94 00:05:13.650 --> 00:05:17.760 This flexibility is important for system administrators 95 00:05:17.760 --> 00:05:21.870 who need to schedule things like automated security scans 96 00:05:21.870 --> 00:05:24.150 or regular system checks 97 00:05:24.150 --> 00:05:27.030 to keep the system running smoothly. 98 00:05:27.030 --> 00:05:30.600 Scheduling tasks in advance helps ensure 99 00:05:30.600 --> 00:05:34.620 that critical operations are carried out on time, 100 00:05:34.620 --> 00:05:38.460 improving system stability and security. 101 00:05:38.460 --> 00:05:41.010 Additionally, Scheduled Tasks can work 102 00:05:41.010 --> 00:05:46.010 alongside PowerShell scripts to automate a variety of tasks. 103 00:05:46.020 --> 00:05:49.680 For example, a PowerShell script could be scheduled 104 00:05:49.680 --> 00:05:54.090 to scan logs for errors, send alerts for potential issues, 105 00:05:54.090 --> 00:05:57.660 or automatically back up important files. 106 00:05:57.660 --> 00:06:02.220 This integration allows for powerful automated workflows 107 00:06:02.220 --> 00:06:06.210 that help administrators keep the system running efficiently 108 00:06:06.210 --> 00:06:09.210 without needing to constantly monitor 109 00:06:09.210 --> 00:06:12.000 or manually trigger these tasks. 110 00:06:12.000 --> 00:06:13.410 So automation 111 00:06:13.410 --> 00:06:16.950 through Scheduled Tasks greatly reduces the workload 112 00:06:16.950 --> 00:06:18.990 for system administrators. 113 00:06:18.990 --> 00:06:21.960 Overall, Scheduled Tasks are used 114 00:06:21.960 --> 00:06:24.030 for automating system maintenance 115 00:06:24.030 --> 00:06:26.970 and management in Windows environments. 116 00:06:26.970 --> 00:06:30.450 By scheduling tasks to run at regular intervals, 117 00:06:30.450 --> 00:06:33.750 administrators can ensure the important processes 118 00:06:33.750 --> 00:06:38.730 like updates, backups, and scans are performed consistently 119 00:06:38.730 --> 00:06:40.230 and on time. 120 00:06:40.230 --> 00:06:44.490 This helps reduce human error, maintain system security, 121 00:06:44.490 --> 00:06:48.900 and free up administrators to focus on more critical tasks. 122 00:06:48.900 --> 00:06:51.600 Now let's conduct a demonstration 123 00:06:51.600 --> 00:06:54.240 of the Linux Cron capability. 124 00:06:54.240 --> 00:06:55.920 In this demonstration, 125 00:06:55.920 --> 00:07:00.870 I'm going to run a script every day at 7:00 AM 126 00:07:00.870 --> 00:07:04.260 using the crontab in Linux. 127 00:07:04.260 --> 00:07:07.980 To do this, I've created the following script. 128 00:07:07.980 --> 00:07:10.503 Let me go ahead and bring it up on the screen. 129 00:07:15.090 --> 00:07:18.270 This is a bash script that searches for 130 00:07:18.270 --> 00:07:21.960 and extracts log entries containing information 131 00:07:21.960 --> 00:07:25.200 about the NetworkManager service 132 00:07:25.200 --> 00:07:28.121 from the systems journal logs. 133 00:07:28.121 --> 00:07:29.451 The script begins 134 00:07:29.451 --> 00:07:34.451 by displaying the message Pulling NetworkManager entries 135 00:07:34.452 --> 00:07:38.173 to inform the user that the script is running. 136 00:07:38.173 --> 00:07:41.715 Next, the journalctl command is used 137 00:07:41.715 --> 00:07:45.870 to search the system's journal logs for entries specific 138 00:07:45.870 --> 00:07:49.350 to the NetworkManager service. 139 00:07:49.350 --> 00:07:54.350 Matching entries are processed using the cut command, 140 00:07:54.510 --> 00:07:58.680 extracting the first five fields of each line, 141 00:07:58.680 --> 00:08:01.140 which typically include the timestamp 142 00:08:01.140 --> 00:08:03.330 and initial log data. 143 00:08:03.330 --> 00:08:07.200 The resulting output is saved into a new file 144 00:08:07.200 --> 00:08:11.190 named netman-log.txt. 145 00:08:11.190 --> 00:08:16.190 Finally, the script prints NetworkManager log file created 146 00:08:16.740 --> 00:08:18.120 to inform the user 147 00:08:18.120 --> 00:08:21.390 that the log extraction process is complete 148 00:08:21.390 --> 00:08:24.390 and the new file has been created. 149 00:08:24.390 --> 00:08:28.830 This script automates the extraction of specific log entries 150 00:08:28.830 --> 00:08:30.960 for easier review. 151 00:08:30.960 --> 00:08:32.670 In this demonstration, 152 00:08:32.670 --> 00:08:36.723 I have created this netman-log.shscript, 153 00:08:37.650 --> 00:08:42.650 made it executable and stored it in my documents folder. 154 00:08:42.810 --> 00:08:45.540 To get it set up to run automatically, 155 00:08:45.540 --> 00:08:49.080 let's first open the Linux crontab editor 156 00:08:49.080 --> 00:08:53.943 with the following command, crontab -e. 157 00:08:55.980 --> 00:09:00.980 This is the crontab file where we can schedule tasks. 158 00:09:01.230 --> 00:09:06.230 We are going to add a line to this crontab editor 159 00:09:06.630 --> 00:09:09.030 to run our script. 160 00:09:09.030 --> 00:09:12.780 I've already added the line in here, but it's commented out, 161 00:09:12.780 --> 00:09:16.680 so I'll go ahead and uncomment it right here. 162 00:09:16.680 --> 00:09:19.530 This line will execute our script. 163 00:09:19.530 --> 00:09:23.400 Let's go through and understand exactly what it's doing. 164 00:09:23.400 --> 00:09:26.610 In the crontab for a scheduled task, 165 00:09:26.610 --> 00:09:31.110 there are five asterisk positions associated with the task. 166 00:09:31.110 --> 00:09:33.270 Here's what each one means. 167 00:09:33.270 --> 00:09:35.640 The first asterisk position 168 00:09:35.640 --> 00:09:39.150 specifies the exact minute the task will run, 169 00:09:39.150 --> 00:09:41.940 which in this case is zero minutes, 170 00:09:41.940 --> 00:09:44.043 meaning the start of the hour. 171 00:09:45.300 --> 00:09:48.810 The second asterisk position specifies the hour 172 00:09:48.810 --> 00:09:52.410 of execution, which in this case is the seventh hour 173 00:09:52.410 --> 00:09:55.023 of the day or 7:00 AM. 174 00:09:56.190 --> 00:10:01.190 The third position identifies a specific day of the month 175 00:10:03.540 --> 00:10:05.160 to run the task, 176 00:10:05.160 --> 00:10:07.740 which in this case is not being used, 177 00:10:07.740 --> 00:10:11.220 so the task will run on all days of the month. 178 00:10:11.220 --> 00:10:15.150 The fourth asterisk position identifies a month 179 00:10:15.150 --> 00:10:17.310 the task should execute, 180 00:10:17.310 --> 00:10:19.650 which in this case is not being used, 181 00:10:19.650 --> 00:10:23.010 so the task will run regardless of the month. 182 00:10:23.010 --> 00:10:26.610 The fifth asterisk position indicates a day 183 00:10:26.610 --> 00:10:29.610 of the week the task should execute, 184 00:10:29.610 --> 00:10:32.670 starting with day one as Monday. 185 00:10:32.670 --> 00:10:35.070 In this case, this asterisks position 186 00:10:35.070 --> 00:10:36.990 is also not being used, 187 00:10:36.990 --> 00:10:41.460 so the task will run every day Monday through Sunday. 188 00:10:41.460 --> 00:10:45.513 Now, let's exit and save the crontab editor. 189 00:10:46.830 --> 00:10:49.080 Next, we need to confirm 190 00:10:49.080 --> 00:10:52.080 that the cron job is successfully added 191 00:10:52.080 --> 00:10:57.060 by taking a look at the crontab and listing its contents. 192 00:10:57.060 --> 00:11:02.060 We'll do this with the following crontab -l command. 193 00:11:02.940 --> 00:11:06.660 And there we see, we can see the modified crontab, 194 00:11:06.660 --> 00:11:10.593 and we can see that our scheduled task is active. 195 00:11:11.490 --> 00:11:14.310 We've done now what we set out to do, 196 00:11:14.310 --> 00:11:17.190 which is to create a crontab entry 197 00:11:17.190 --> 00:11:21.360 to run a script every day at 7:00 AM 198 00:11:21.360 --> 00:11:23.910 but we want to see it happen. 199 00:11:23.910 --> 00:11:26.760 Let's start out by modifying the crontab 200 00:11:26.760 --> 00:11:30.000 to trigger our script within the next minute. 201 00:11:30.000 --> 00:11:35.000 We'll start off with the crontab -e command 202 00:11:36.810 --> 00:11:39.930 to be able to access our file. 203 00:11:39.930 --> 00:11:43.620 Now, looking up at the top right hand part of my screen, 204 00:11:43.620 --> 00:11:48.620 I see that the time just rolled over to 16:08. 205 00:11:49.050 --> 00:11:53.190 So knowing that the first asterisk position is the minute, 206 00:11:53.190 --> 00:11:55.680 I'm going to set that for minute nine, 207 00:11:55.680 --> 00:11:59.430 and I know that the second asterisk position is the hour. 208 00:11:59.430 --> 00:12:02.430 I'm going to set that for 16. 209 00:12:02.430 --> 00:12:04.833 Now let me save this and exit out. 210 00:12:06.450 --> 00:12:08.010 Now all we need to do 211 00:12:08.010 --> 00:12:10.920 is wait until the next minute clicks over, 212 00:12:10.920 --> 00:12:12.330 and if it works, 213 00:12:12.330 --> 00:12:16.920 we should see a netman-log.txt file appear 214 00:12:16.920 --> 00:12:19.080 in our documents folder. 215 00:12:19.080 --> 00:12:21.420 You can see in that folder right now, 216 00:12:21.420 --> 00:12:26.080 we just have our script, the netman-log.sh file. 217 00:12:27.870 --> 00:12:30.450 So we'll wait that one minute 218 00:12:30.450 --> 00:12:33.600 and then see that the text file shows up 219 00:12:33.600 --> 00:12:35.883 once the script is executed. 220 00:12:40.170 --> 00:12:43.680 Alright, it's just turned to 16:09. 221 00:12:43.680 --> 00:12:47.490 So let's check to see if our script executed. 222 00:12:47.490 --> 00:12:51.180 I'll list the file contents with the ls command. 223 00:12:51.180 --> 00:12:52.110 And there it is. 224 00:12:52.110 --> 00:12:57.110 You can see that our netman-log.txt file has been created. 225 00:12:59.970 --> 00:13:03.780 And you can see that it is populated with information. 226 00:13:03.780 --> 00:13:07.260 So we have just demonstrated the execution 227 00:13:07.260 --> 00:13:12.260 of a scheduled task with the crontab on a Linux machine. 228 00:13:12.660 --> 00:13:16.020 This is the end of our demonstration. 229 00:13:16.020 --> 00:13:21.020 So remember, Cron and Scheduled Tasks are tools 230 00:13:21.420 --> 00:13:24.330 used for automating tasks on Linux 231 00:13:24.330 --> 00:13:27.060 and Windows systems respectively. 232 00:13:27.060 --> 00:13:31.230 Cron is a job scheduler in Linux that allows users 233 00:13:31.230 --> 00:13:34.350 to automate tasks like security scans 234 00:13:34.350 --> 00:13:38.220 or log updates by specifying the exact time 235 00:13:38.220 --> 00:13:40.950 and frequency of execution. 236 00:13:40.950 --> 00:13:45.090 Scheduled Tasks in Windows serve a similar purpose, 237 00:13:45.090 --> 00:13:48.000 enabling automation for tasks such 238 00:13:48.000 --> 00:13:52.740 as running maintenance scripts or performing system updates. 239 00:13:52.740 --> 00:13:56.280 Both tools help system administrators ensure 240 00:13:56.280 --> 00:14:00.930 that tasks run consistently without manual intervention. 241 00:14:00.930 --> 00:14:04.380 This automation reduces human error, 242 00:14:04.380 --> 00:14:06.510 improves system security, 243 00:14:06.510 --> 00:14:09.753 and enables efficient system maintenance.