RHEL: Figuring out CPUs, Cores and Hyper-Threading

Hi all!
It’s a recurrent subject, right? But no one is 100% sure to how figure this out… So, let me quickly show you my way:

– Physical CPUs (sockets):

[root@mysrvr ~]# grep -i "physical id" /proc/cpuinfo | sort -u | wc -l
[root@mysrvr ~]# dmidecode -t processor |grep CPU
        Version: Intel(R) Xeon(R) CPU X5570 @ 2.93GHz
        Version: Intel(R) Xeon(R) CPU X5570 @ 2.93GHz

So, 2 physical CPUs.

– Physical Cores

[root@mysrvr ~]# egrep -e "core id" -e ^physical /proc/cpuinfo|xargs -l2 echo|sort -u
physical id : 0 core id : 0
physical id : 0 core id : 1
physical id : 0 core id : 2
physical id : 0 core id : 3
physical id : 1 core id : 0
physical id : 1 core id : 1
physical id : 1 core id : 2
physical id : 1 core id : 3

Each one of Physical Processors has 4 cores.
So, there is two quad-cores. This way, we have 8 cores at all.

– Logical CPUs

[root@mysrvr ~]# grep -i "processor" /proc/cpuinfo | sort -u | wc -l

Ok, so we have cores in double.
This means we have Hyper-Threading (technology by Intel Processors).

Not so hard, right?

Those links are similar and quite cool to understand the concepts:


“tail -f” vs “tail -F”: Do you know the difference?

Hi all!
Do you know the difference between “tail -f” and “tail -F”?


Ok, don’t feel bad. It’s very difficult to find someone who knows… And with a reason, I can’t find any link explaining this by Googling.
It’s possible that I don’t know how to search it too. But I searched as I’d search if I didn’t know that… And couldn’t find anything about…

Let’s take a look on –help, so:

Continue reading

Installing and Configuring ASMLIb on Oracle Linux 7

Hi all!
For those are familiar with RHEL/OEL 4 and 5, there is some differences to start ASMLib on OEL 6 and 7.

So, a quick guide to install (done on OEL 7), start and configure:

1. Install the ASMLib kernel module package as root using the following command:

yum install kmod-oracleasm

2. Install the ASMLib library package and utilities package

yum install oracleasm-support oracleasmlib oracleasm-`uname -r`

It’s possible some package to not found. For example:

No package oracleasmlib available.

So, you can download rpm libs from here and install via rpm:

[root@dbsrv01 oracle]# rpm -Uvh ~/oracleasmlib-2.0.12-1.el6.x86_64.rpm
Preparing...                          ################################# [100%]
Updating / installing...
1:oracleasmlib-2.0.12-1.el6        ################################# [100%]

Ok, now, lets configure/start services:

[root@dbsrv01 ~]# /etc/init.d/oracleasm configure

Nothing happen? Ok, let’s try to start it:

[root@dbsrv01 ~]# /etc/init.d/oracleasm start
Starting oracleasm (via systemctl):  Job for oracleasm.service failed because the control process exited with error code. See "systemctl status oracleasm.service" and "journalctl -xe" for details.

Hmmm… Are these commands correct?

[root@dbsrv01 ~]# /etc/init.d/oracleasm
Usage: /etc/init.d/oracleasm {configure|createdisk|deletedisk|querydisk|listdisks|scandisks|status}

Ok… So, what to do?

Take a look:

[root@dbsrv01 ~]# oracleasm init
Creating /dev/oracleasm mount point: /dev/oracleasm
Loading module "oracleasm": oracleasm
Configuring "oracleasm" to use device physical block size
Mounting ASMlib driver filesystem: /dev/oracleasm

Now, let’s configure:

[root@dbsrv01 ~]# oracleasm configure

It shows, but how configure?

Just put “-i” clause, like:

[root@dbsrv01 ~]# oracleasm configure -i
Configuring the Oracle ASM library driver.
This will configure the on-boot properties of the Oracle ASM library
driver.  The following questions will determine whether the driver is
loaded on boot and what permissions it will have.  The current values
will be shown in brackets ('[]').  Hitting  without typing an
answer will keep that current value.  Ctrl-C will abort.
Default user to own the driver interface []: grid
Default group to own the driver interface []: oinstall
Scan for Oracle ASM disks on boot (y/n) [y]: y
Writing Oracle ASM library driver configuration: done

And you can list again:

[root@dbsrv01 ~]# oracleasm configure
[root@dbsrv01 ~]# oracleasm status
Checking if ASM is loaded: yes
Checking if /dev/oracleasm is mounted: yes

To add a disk, the same process can be followed on earlier versions:

[root@dbsrv01 ~]# oracleasm createdisk SDD /dev/sdd1
Writing disk header: done
Instantiating disk: done
[root@dbsrv01 ~]# oracleasm listdisks

For all commands:

[root@dbsrv01 ~]# oracleasm -h
Usage: oracleasm [--exec-path=]  [  ]
oracleasm --exec-path
oracleasm -h
oracleasm -V
The basic oracleasm commands are:
configure        Configure the Oracle Linux ASMLib driver
init             Load and initialize the ASMLib driver
exit             Stop the ASMLib driver
scandisks        Scan the system for Oracle ASMLib disks
status           Display the status of the Oracle ASMLib driver
listdisks        List known Oracle ASMLib disks
querydisk        Determine if a disk belongs to Oracle ASMlib
createdisk       Allocate a device for Oracle ASMLib use
deletedisk       Return a device to the operating system
renamedisk       Change the label of an Oracle ASMlib disk
update-driver    Download the latest ASMLib driver

And to see arguments for each one:

[root@dbsrv01 ~]# oracleasm configure -h
Usage: oracleasm-configure [-l ] [-i|-I] [-e|-d] [-u ] [-g ] [-b|-p] [-s y|n] [[-o ] ...] [[-x ] ...]

Have a nice day!
See ya!

nc -l – Starting up a fake service

Hi everyone!

Recently i have faced a situation that made me find out a very nice and useful command that helped me a lot, and i hope it comes to help you guys as well, and it’s named:


Situation: We have a replicated environment from one datacenter to another (Using Golden Gate), where the ETL happens. So basically is:

Datacenter 1 (root data)

Replicates to datacenter 2 (transforming the data)

that replicates to datacenter 3 (production itself)

In Datacenter level 2, we have a dataguard configured. So then came the question:

  • What if we need to do the switchover to the standby environments?
  • Will we gonna have everything we need properly set up for the replication?
  • How are we going to test the ports if nothing is up in there? Aren’t we gonna get “connection refused”?

Calm down! There is a very nice workaround for this.

All you need to do is install the nc command as root (if it is not installed already):

yum install nc

Then execute it as follows, on the server you wanna test:

nc -l


I wanna make sure that on the standby server the port 7809 (Golden Gate MANAGER port) is open. On the standby server you run:

nc -l 7809

Then, from a remote server, you are going to be able to connect through a simple telnet command:

telnet server.domain port


telnet standby.company.com 7809



  • Try the telnet from the remote server to the standby:

remoteserver {/home/oracle}: telnet standby.server 7809


telnet: connect to address Connection refused

  • Then we start the fake service on the standby server!

standby.server {/home/oracle}: nc -l 7809

  • And try the telnet again:

remoteserver {/home/oracle}: telnet standby.server 7809


Connected to standby.server.

Escape character is ‘^]’.




Linux: Resizing Swap Online

Hi all!
Quick one to resize swap online:

[root@server-db ~]# swapon -s
Filename                                Type            Size    Used    Priority
/dev/mapper/rootvg-lvswap              partition       5242872 373624  -1
[root@server-db ~]# vgs
VG                #PV #LV #SN Attr   VSize   VFree
rootvg              1   6   0 wz--n- 135.69G 5.69G
[root@server-db ~]# lvextend -L +2048M /dev/mapper/rootvg-lvswap
Extending logical volume lvswap to 7.00 GB
Logical volume lvswap successfully resized
[root@server-db ~]# vgs
VG                #PV #LV #SN Attr   VSize   VFree
rootvg              1   6   0 wz--n- 135.69G 3.69G
[root@server-db ~]# mkswap /dev/mapper/rootvg-lvswap
Setting up swapspace version 1, size = 7516188 kB
[root@server-db ~]# swapoff /dev/mapper/rootvg-lvswap
[root@server-db ~]# swapon /dev/mapper/rootvg-lvswap
[root@server-db ~]# swapon -s
Filename                                Type            Size    Used    Priority
/dev/mapper/rootvg-lvswap              partition       7516188 373624  -1

See ya!