My web server’s log file size is quite huge or large. How do I delete a log file in Linux without disturbing running application? Is there a proper way to clear log files on Unix?
You can simply truncate a log file using > filename syntax. For example if log file name is /var/log/foo, try > /var/log/foo as root user.
How to clear the contents of a log file from the command line
Say you want to clear the contents of a log file named /var/log/messages, run:# >/var/log/messages
The following is compatible with various Linux or Unix shells:: > /var/log/messages
Verify file size:# ls -l /var/log/messages
If you really wanted to delete or remove a file type the following rm command:# rm /var/log/message
Delete a log files in Linux or UNIX using truncate
Use the truncate command to shrink or extend the size of each FILE to the specified size. So a proper way to clear log file named www.cyberciti.biz_access.log is to run the following command:# cd /var/log/nginx/
# ls -lh www.cyberciti.biz_access.log
# truncate -s 0 www.cyberciti.biz_access.log
# ls -lh www.cyberciti.biz_access.log
Other commands to empty or delete a large file content in Linux
Try the cat command:cat /dev/null > www.cyberciti.biz_access.log
Or the cp command:# cp /dev/null /var/log/nginx/php_error.log
How do I clear log file using dd on Linux or Unix?
Type dd command as follows:# dd if=/dev/null of=/path/to/log/file
# dd if=/dev/null of=/var/log/lighttpd/error_log
How to empty or truncate a file in Linux using echo/printf
One more method is to use the echo command:# echo -n "" > /path/to/java/appserver.log
Say hello to logrotate tool
A better approach is to use logrotate tool. It is designed to ease administration of systems that generate large numbers of log files. It allows automatic rotation, compression, removal, and mailing of log files. Each log file may be handled daily, weekly, monthly, or when it grows too large. See my previous logrotate help page:
Conclusion
This page showed how to empty or delete a large log file contents in Linux and Unix like systems. There are other methods too as discussed in the comments section below.