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Red Hat Enterprise Linux Troubleshooting Guide

You're reading from   Red Hat Enterprise Linux Troubleshooting Guide Identify, capture and resolve common issues faced by Red Hat Enterprise Linux administrators using best practices and advanced troubleshooting techniques

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Product type Paperback
Published in Oct 2015
Publisher
ISBN-13 9781785283550
Length 458 pages
Edition 1st Edition
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Author (1):
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Benjamin Cane Benjamin Cane
Author Profile Icon Benjamin Cane
Benjamin Cane
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Table of Contents (14) Chapters Close

Preface 1. Troubleshooting Best Practices 2. Troubleshooting Commands and Sources of Useful Information FREE CHAPTER 3. Troubleshooting a Web Application 4. Troubleshooting Performance Issues 5. Network Troubleshooting 6. Diagnosing and Correcting Firewall Issues 7. Filesystem Errors and Recovery 8. Hardware Troubleshooting 9. Using System Tools to Troubleshoot Applications 10. Understanding Linux User and Kernel Limits 11. Recovering from Common Failures 12. Root Cause Analysis of an Unexpected Reboot Index

Changing user limits


Since we suspect the open files limit is preventing the application from executing, we can set its limit to a higher value. However, this is not as simple as executing ulimit –n; the following output is what we get when it's executed:

$ ulimit -n
1024
$ ulimit -n 5000
-bash: ulimit: open files: cannot modify limit: Operation not permitted
$ ulimit -n 4096
$ ulimit -n
4096

By default, on our example system the highest the vagrant user is allowed to raise the open files limitation to is 4096. As we can see from the preceding error, anything higher is denied; but like most things with Linux we can change this.

The limits.conf file

The user limits that we have been using and modifying are part of Linux's PAM system. PAM or Pluggable Authentication Modules is a system that provides a modular authentication system.

For example, if our system was to utilize LDAP for authentication, the pam_ldap.so library would be used to provide this functionality. However, since our system uses...

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