Disabling Transparent HugePages in RHEL7.x

[root@lab-12cr2 ~]# cat /etc/redhat-release
Red Hat Enterprise Linux Server release 7.0 (Maipo)

Runtime Disable THP
Append below lines in /etc/rc.local
if test -f /sys/kernel/mm/transparent_hugepage/enabled; then
echo never > /sys/kernel/mm/transparent_hugepage/enabled
if test -f /sys/kernel/mm/transparent_hugepage/defrag; then
echo never > /sys/kernel/mm/transparent_hugepage/defrag
Make sure that rc.local is running on reboot
chmod +x /etc/rc.d/rc.local
systemctl enable rc-local
systemctl status rc-local

Check the behavior on post reboot the operating system

[root@lab-12cr2 ~]# cat /sys/kernel/mm/transparent_hugepage/enabled
always madvise [never]
[root@lab-12cr2 ~]#
[root@lab-12cr2 ~]# cat /sys/kernel/mm/transparent_hugepage/defrag
always madvise [never]
[root@lab-12cr2 ~]#
[root@lab-12cr2 ~]# grep -i HugePages_Total /proc/meminfo
HugePages_Total: 0
[root@lab-12cr2 ~]# cat /proc/sys/vm/nr_hugepages
[root@lab-12cr2 ~]# grep -i AnonHugePages /proc/meminfo
AnonHugePages: 2048 kB

Permanent Disable THP
Oracle Linux 7 is similar, but uses GRUB2 so you need to edit the “/boot/grub2/grub.cfg” file using the grubby command.
[root@lab-12cr2 ~]# grubby –default-kernel
[root@lab-12cr2 ~]# grubby –args=”transparent_hugepage=never” –update-kernel /boot/vmlinuz-3.10.0-123.el7.x86_64
[root@lab-12cr2 ~]# grubby –info /boot/vmlinuz-3.10.0-123.el7.x86_64
args=”ro rd.lvm.lv=rhel/root crashkernel=auto rd.lvm.lv=rhel/swap vconsole.font=latarcyrheb-sun16 vconsole.keymap=us rhgb quiet LANG=en_US.UTF-8 transparent_hugepage=never”
title=Red Hat Enterprise Linux Server, with Linux 3.10.0-123.el7.x86_64
[root@lab-12cr2 ~]#

[root@lab-12cr2 ~]# grep -i “transparent_hugepage=never” /boot/grub2/grub.cfg
linux16 /vmlinuz-3.10.0-123.el7.x86_64 root=UUID=8190d97a-a2e9-44cd-9810-804def1d6f89 ro rd.lvm.lv=rhel/root crashkernel=auto rd.lvm.lv=rhel/swap vconsole.font=latarcyrheb-sun16 vconsole.keymap=us rhgb quiet LANG=en_US.UTF-8 transparent_hugepage=never
[root@lab-12cr2 ~]# grep -i AnonHugePages /proc/meminfo
AnonHugePages: 0 kB
[root@lab-12cr2 ~]#
[root@lab-12cr2 ~]# grep -i HugePages_Total /proc/meminfo
HugePages_Total: 0
[root@lab-12cr2 ~]# cat /proc/sys/vm/nr_hugepages

Oracle MetaLink ALERT: Disable Transparent HugePages on SLES11, RHEL6, RHEL7, OL6, OL7 and UEK2 Kernels (Doc ID 1557478.1)



Behavior Changes of RHEL 7.x Operating System

RHEL 7.x had taken lots of changes by default …

1.) Default file system changes: XFS
In RHEL7 /CentOS 7 and Oracle Linux have adopted XFS as their default file system.
Apart of these there are other numerous changes that you could find from faq forum like http://simplylinuxfaq.blogspot.in/p/major-difference-between-rhel-7-and-6.html

Some of them i found to be mandatory change before use it for Database Server in Production.
2.) Default HugePages is On On
Oracle recommends that you disable Transparent HugePages before you start installation.

3.) Default Setting RemoveIPC=yes
Setting RemoveIPC=yes on Redhat 7.2 Crashes ASM and Database Instances as Well as Any Application That Uses a Shared Memory Segment (SHM) or Semaphores (SEM)

Recommended to follow below steps
1. Set RemoveIPC=no in /etc/systemd/logind.conf
2. Reboot the server or restart systemd-logind as follows:
# systemctl daemon-reload
# systemctl restart systemd-logind

RHEL7: rc.local service not starting

Found this on some Red Hat blog:

“Systemd is a system and service manager for Linux operating systems. It is designed to be backwards compatible with SysV init scripts, and provides a number of features such as parallel startup of system services at boot time, on-demand activation of daemons, support for system state snapshots, or dependency-based service control logic. In Red Hat Enterprise Linux 7, systemd replaces Upstart as the default init system.”

chmod +x /etc/rc.d/rc.local
systemctl enable rc-local
systemctl status rc-local


How to protect your cronjob in linux ?


A very useful Linux tip on how to make files and directories undeletable even by the root user. You can apply this tip on all important configuration files so that no one accidentally or intentionally deletes it. To achieve this the chattr (Change Attribute) command is used it Linux. The chattr command “immunizes” the file not only from deletion but also modification. The chattr command does care about chmod values, even if a file has 777 permissions immunizing the file will prevent it from being deleted or modified.

chattr +i /path/to/filename

How to view file attributes ?
lsattr /path/to/directory

How to remove the immutable flag ?
chattr -i /path/to/file


Advanced Linux Commands on Oracle Technology Network

Advanced Linux Commands. on Oracle Technology Network