Confguration of Kerberos V5 1. Install krb5-libs, krb5-server, and krb5-workstation packages 2. Edit the /etc/krb5.conf and /var/kerberos/krb5kdc/kdc.conf to reflect your realm name and domain to realm mappings. A simple realm can be constructed by replacing instances of EXAMPLE.COM and example.com with your domain name (making sure you keep the same case), and by changing kerberos.example.com to the fully qualified hostname of the server. For example: # cat /etc/krb5.conf [logging] … [Read more...] about How to Install and Configure Kerberos in CentOS/RHEL 7
–force V/s –nodeps : rpm command options to install or uninstall a package
These rpm options can potentially corrupt a Linux server so severely a reinstall may become necessary. So be cautious while playing with them. --force V/s --nodeps --force Ignore package and file conflicts for install -- package might stop working properly leading to serious issues --nodeps Do not check dependencies -- package might not work properly after using this flag ( or dependent packages might stop working ) Often one RPM package requires one or more other RPM packages to … [Read more...] about –force V/s –nodeps : rpm command options to install or uninstall a package
Linux “rm” Command Examples
Unix includes two commands that you can use to delete files and directories: rm (remove) and rmdir (remove directory). You can also use "rm" command to remove a directory as well. In this post, we are going to discuss on rm command in Linux. rm is a Linux terminal command used to delete/remove files & directories. It’s completely free application comes as in build application with Linux OS Installation. The main author of this application is Paul Rubin, Richard M. Stallman, Jim Meyering and … [Read more...] about Linux “rm” Command Examples
Oracle Database 12c2 : CPU_COUNT is Wrong
The Problem On Oracle database 12.2.0.1 version, cpu_count is not correct: OS has 128 CPU in total, however CPU_COUNT is only 104. SQL> show parameter cpu NAME TYPE VALUE ------------------------------------ ----------- ------------------------------ cpu_count integer 104 … [Read more...] about Oracle Database 12c2 : CPU_COUNT is Wrong
How to configure resource groups for MySQL Server running on Linux
The following provides the procedure for configuring and using resource groups under Linux: 1. To use cgroups, you must install the "libcgroup" package on your system: # yum install libcgroup 2. Create a config file for cgroups: # vi /etc/cgconfig.conf mount { cpu = /cgroup/cpumem; cpuset = /cgroup/cpumem; memory = /cgroup/cpumem; } # High priority group group mysqldb { cpu { # Allocate the relative share of CPU resources equal to 75% cpu.shares="750"; } cpuset { # No … [Read more...] about How to configure resource groups for MySQL Server running on Linux
How to Create and Query a BTRFS File System
The Basics The btrfs file system is designed to meet the expanding scalability requirements of large storage subsystems. As the btrfs file system uses B-trees in its implementation, its name derives from the name of those data structures, although it is not a true acronym. A B-tree is a tree-like data structure that enables file systems and databases to efficiently access and update large blocks of data no matter how large the tree grows. The btrfs file system provides the following … [Read more...] about How to Create and Query a BTRFS File System
How to configure CentOS/RHEL 6 system to not used last 3 passwords used
Question: How to change the password policy on a system so that a user cannot choose any of the last 3 passwords previously used? 1. Make sure that the file /etc/security/opasswd has the default permission (600). # ls -l /etc/security/opasswd -rw------- 1 root root 116 Sep 8 14:52 /etc/security/opasswd 2. Ensure you backup the file /etc/pam.d/system-auth: # cp /etc/pam.d/system-auth /etc/pam.d/system-auth.old 3. Modify the file /etc/pam.d/system-auth in vi editor and change the line … [Read more...] about How to configure CentOS/RHEL 6 system to not used last 3 passwords used
How to Customize Linux Password Expiration and Complexity Requirements
1. Password Expiration To set the default password expiration when creating new accounts on CentOS/RHEL, edit the /etc/login.defs file. PASS_MAX_DAYS 100 Which means the maximum number of days a password may be used. Please check man page of login.defs for more options that can be set in /etc/login.defs.: $ man login.defs 2. Password Complexity The PAM module pam_cracklib can be used to force password complexity requirements. The complexity can be specified with the following … [Read more...] about How to Customize Linux Password Expiration and Complexity Requirements
Solaris Interview Questions – Inodes and the Filesystem Troubleshooting
1. Why 'du' and 'df' reports different values? - df describes disk usage. - du adds up the size all the files on a filesystem. They can report wildly different figures. One reason: Processes write to files. files can be deleted while processes are writing to files. So a file may be gone, but its inode may not be freed up. For example: # cat > bogus testing testing ^Z Stopped (user) # ls -i bogus 2921 bogus # fuser bogus bogus: 14947o # rm bogus # ls -i bogus bogus: No … [Read more...] about Solaris Interview Questions – Inodes and the Filesystem Troubleshooting
How To Masquerade Sender Address In Sendmail in CentOS/RHEL
You would like to configure your sendmail server to masquerade the sender address to no-reply@target-domain.net when sending emails from it. The Solution Normally to masquerade a domain, the "MASQUERADE_AS" and "MASQUERADE_DOMAIN" is used in /etc/mail/sendmail.mc. But that will leave the user unchanged. With sendmail, you can change both the domain and username on a case-by-case basis using the genericstable feature. 1. make sure all the "MASQUERADE" items are commented out in … [Read more...] about How To Masquerade Sender Address In Sendmail in CentOS/RHEL