Uly.me

cloud engineer

log

Logging Commands

by ·

I decided to log my commands for good record keeping. Here’s my script.

#!/bin/bash
if [[ $# -eq 0 ]] ; then echo 'No arguments. Format: ./go.sh script.sh'; exit 0; fi
log=log.txt
echo '-------------------------------' >> $log
date >> $log
echo '---' >> $log
cat $1 >> $log
echo '---' >> $log
/bin/bash $1 2>&1 | tee -a $log

To run.

./go.sh script.sh

Line by line explanation.

  1. Checks for script to run. Exits if there’s no argument.
  2. Sets the log file.
  3. Prints dashes.
  4. Prints the date.
  5. Print 3 dashes.
  6. Prints the commands to the log file.
  7. Print 3 dashes.
  8. Run the command. Send error and standard out to log file.

Setup Log Rotation

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Logrotation is available in most Linux distros. If they are missing, you can easily install them. The logrotation main configuration file is located in /etc/logrotate.conf which is the default setting. The config file contains an include statement that pulls in other log configurations located in the /etc/logrotate.d/ directory. When setting up a log rotation, it’s best to add your log rotation configuration in this directory.

Here’s a simple configuration in a file called webmon.

/home/ubuntu/webmon.log {
        daily
        create 0640 ubuntu ubuntu
        dateext
        rotate 7
	nocompress
}

The options above does the following:

  • The logs are rotated daily.
  • The logs are rotated 7 times with no compression.
  • The rotate log files will have dates appended to them.
  • The log files are owned user ubuntu with permission of 0640.

There are more options from the logrotate man pages which can be added.

Audit Log Files

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The /var/log/audit/audit.log files were not being rotated. The files in the directory grew so large that it created disk space issues on /. Here’s the fix. In the /etc/audit/auditd.conf file, change max_log_file_action from “ignore” to “rotate.” Instead of hundreds of files being kept, it will be rotated up to 5 files. 

max_log_file_action = rotate
num_logs = 5

Restart service to take effect. The old files will be deleted.

service auditd stop
service auditd start
service auditd status

Disk space went from 82% down to 25%.

Internet Test

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My internet has been flaky lately. I wrote a script that logs my internet connection.

I’m running it in cron every minute.

#!/bin/bash
log='/home/ulysses/Code/spectrum.log'
if nc -zw1 google.com 443;
then 
  echo 'Spectrum is up' $(date) >> $log
else 
  echo 'Spectrum is down' $(date) >> $log
fi

To view, just cat the log.

cat spectrum.log 
Spectrum is up Fri Jun 26 15:14:01 EDT 2020
Spectrum is up Fri Jun 26 15:15:01 EDT 2020
Spectrum is up Fri Jun 26 15:16:01 EDT 2020
Spectrum is up Fri Jun 26 15:17:01 EDT 2020
Spectrum is up Fri Jun 26 15:18:01 EDT 2020

So, I now have a record when it was up or down.