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Linux and Unix nohup command

20 de outubro de 2016 2 Comentários

About nohup

When using the command shell, prefixing a command with nohup prevents the command from being aborted if you log out or exit the shell.
The name nohup stands for “no hangup.” The hangup (HUP) signal, which is normally sent to a process to inform it that the user has logged off (or “hung up”), is intercepted by nohup, allowing the process to continue running.

Nohup syntax

nohup COMMAND [ARG]...

nohup OPTION...

Options

--help display a help message and exit.

--version output version information and exit.

If standard input is a terminal, nohup redirects it from /dev/null. If standard output is a terminal, append output to “nohup.out” if possible, “$HOME/nohup.out” otherwise. If standard error is a terminal, redirect it to standard output. To save output to file FILE, use “nohup COMMAND > FILE”.

Nohup examples

nohup find -size +100k > log.txt &
Run the find command, instructing it to search for any file bigger then 100 kilobytes. find will continue to search even if the user logs out, and write its results to the file log.txt.
The “&” symbol at the end of the command runs find in the background, returning you to the command prompt while it is running. It is normal to use nohup in conjunction with & if you want to continue running other commands.

Related commands

nice — Invoke a command with an altered scheduling priority.

Database, Linux, Oracle, RedHat 7

Oracle Database 12c Release Installation On Oracle Linux 7

22 de agosto de 2016 37 Comentários

Download Software

Download the Oracle software from OTN or MOS depending on your support status.

OTN: Oracle Database 12c Release 1 (12.1.0.2) Software (64-bit).
edelivery: Oracle Database 12c Release 1 (12.1.0.2) Software (64-bit)

This article has been updated for the 12.1.0.2 release, but the installation is essentially unchanged since 12.1.0.1. Any variations specific for 12.1.0.1 will be noted.

Depending on your version of VirtualBox and Oracle Linux, there may be some slight variation in how the screen shots look.
Unpack Files

Unzip the files.

unzip linuxamd64_12102_database_1of2.zip
unzip linuxamd64_12102_database_2of2.zip

You should now have a single directory called “database” containing installation files.

Hosts File

The “/etc/hosts” file must contain a fully qualified name for the server.

<IP-address> <fully-qualified-machine-name> <machine-name>

For example.

127.0.0.1       localhost.localdomain  localhost
192.168.0.210   ol7-121.localdomain    ol7-121

Oracle Installation Prerequisites

Perform either the Automatic Setup or the Manual Setup to complete the basic prerequisites. The Additional Setup is required for all installations.

Automatic Setup

If you plan to use the “oracle-rdbms-server-12cR1-preinstall” package to perform all your prerequisite setup, issue the following command.

# yum install oracle-rdbms-server-12cR1-preinstall -y

It is probably worth doing a full update as well, but this is not strictly speaking necessary.

# yum update

Manual Setup

If you have not used the “oracle-rdbms-server-12cR1-preinstall” package to perform all prerequisites, you will need to manually perform the following setup tasks.

Add or amend the following lines in the “/etc/sysctl.conf” file.

fs.file-max = 6815744
kernel.sem = 250 32000 100 128
kernel.shmmni = 4096
kernel.shmall = 1073741824
kernel.shmmax = 4398046511104
net.core.rmem_default = 262144
net.core.rmem_max = 4194304
net.core.wmem_default = 262144
net.core.wmem_max = 1048576
fs.aio-max-nr = 1048576
net.ipv4.ip_local_port_range = 9000 65500

Run the following command to change the current kernel parameters.

/sbin/sysctl -p

Add the following lines to the “/etc/security/limits.conf” file.

oracle soft nofile 1024
oracle hard nofile 65536
oracle soft nproc 16384
oracle hard nproc 16384
oracle soft stack 10240
oracle hard stack 32768

Install the following packages if they are not already present.

# From Public Yum or ULN
yum install binutils -y
yum install compat-libcap1 -y
yum install compat-libstdc++-33 -y
yum install compat-libstdc++-33.i686 -y
yum install gcc -y
yum install gcc-c++ -y
yum install glibc -y
yum install glibc.i686 -y
yum install glibc-devel -y
yum install glibc-devel.i686 -y
yum install ksh -y
yum install libgcc -y
yum install libgcc.i686 -y
yum install libstdc++ -y
yum install libstdc++.i686 -y
yum install libstdc++-devel -y
yum install libstdc++-devel.i686 -y
yum install libaio -y
yum install libaio.i686 -y
yum install libaio-devel -y
yum install libaio-devel.i686 -y
yum install libXext -y
yum install libXext.i686 -y
yum install libXtst -y
yum install libXtst.i686 -y
yum install libX11 -y
yum install libX11.i686 -y
yum install libXau -y
yum install libXau.i686 -y
yum install libxcb -y
yum install libxcb.i686 -y
yum install libXi -y
yum install libXi.i686 -y
yum install make -y
yum install sysstat -y
yum install unixODBC -y
yum install unixODBC-devel -y

Create the new groups and users.

groupadd -g 54321 oinstall
groupadd -g 54322 dba
groupadd -g 54323 oper
#groupadd -g 54324 backupdba
#groupadd -g 54325 dgdba
#groupadd -g 54326 kmdba
#groupadd -g 54327 asmdba
#groupadd -g 54328 asmoper
#groupadd -g 54329 asmadmin
#useradd -u 54321 -g oinstall -G dba,oper oracle

Uncomment the extra groups you require.

Additional Setup

The following steps must be performed, whether you did the manual or automatic setup.

Set the password for the “oracle” user.

passwd oracle

Amend the “/etc/security/limits.d/90-nproc.conf” file as described below. See MOS Note [ID 1487773.1]

# Change this
* soft nproc 1024

# To this
* - nproc 16384

Set secure Linux to permissive by editing the “/etc/selinux/config” file, making sure the SELINUX flag is set as follows.

SELINUX=permissive

Once the change is complete, restart the server or run the following command.

# setenforce Permissive

If you have the Linux firewall enabled, you will need to disable or configure it, as shown here or here. To disable it, do the following.

# service iptables stop
# chkconfig iptables off

Create the directories in which the Oracle software will be installed.

mkdir -p /u01/app/oracle/product/12.1.0.2/db_1
chown -R oracle:oinstall /u01
chmod -R 775 /u01

Putting mount points directly under root is typically a bad idea. It’s done here for simplicity, but for a real installation “/” should be reserved for the OS.
Unless you are working from the console, or using SSH tunnelling, login as root and issue the following command.

xhost +<machine-name>

Add the following lines at the end of the “/home/oracle/.bash_profile” file.

# Oracle Settings
export TMP=/tmp
export TMPDIR=$TMP

export ORACLE_HOSTNAME=ol6-121.localdomain
export ORACLE_UNQNAME=cdb1
export ORACLE_BASE=/u01/app/oracle
export ORACLE_HOME=$ORACLE_BASE/product/12.1.0.2/db_1
export ORACLE_SID=cdb1

export PATH=/usr/sbin:$PATH
export PATH=$ORACLE_HOME/bin:$PATH

export LD_LIBRARY_PATH=$ORACLE_HOME/lib:/lib:/usr/lib
export CLASSPATH=$ORACLE_HOME/jlib:$ORACLE_HOME/rdbms/jlib

Installation

Log into the oracle user. If you are using X emulation then set the DISPLAY environmental variable.

DISPLAY=<machine-name>:0.0; export DISPLAY

Start the Oracle Universal Installer (OUI) by issuing the following command in the database directory.

./runInstaller

Proceed with the installation of your choice.

Step 1

Step 2

Step 3

Step 4

Step 5

Step 6

Step 7

Step 8

Step 9

Step 10

Step 11

Step 12

Step 13

Step 14

Step 15

Step 16

Step 17

Step 18

Step 19

Step 20

Step 21

The installation was completed successfully.

Post Installation

Edit the “/etc/oratab” file setting the restart flag for each instance to ‘Y’.

cdb1:/u01/app/oracle/product/12.1.0.2/db_1:Y

If Database Express 12c is not working, check the XMLDB HTTP port. If it is 0, set it to the port you want to use.

SQL> SELECT dbms_xdb_config.gethttpsport FROM dual;
GETHTTPSPORT
------------
5500

SQL> EXEC dbms_xdb_config.sethttpsport(5500);

PL/SQL procedure successfully completed.

SQL>

Common Errors

“error code 35” : The machine name in the “/etc/hosts” file is not correct. It needs an entry for the loopback adapter (localhost) and the machine name. If you are using DNS for name resolution, you still need the loopback adapter reference in this file.
“error code 37” : The DNS not working properly. You may also get this error is the “/etc/hosts” file is not configured correctly.
“sqlplus: error while loading shared libraries: libclntsh.so.12.1” : The prerequisites have not been met. Work through them again. Specifically, make sure the “gcc” package has been installed.
Listener fails to start – Typically this is due to incorrect name resolution. Make sure the “/etc/hosts” and/or DNS is configured correctly.
Linking errors – Almost always due to missing prerequisites. Review the setup sections.

That is all. Any doubts I am available.

CentOS 7, Linux, RedHat 7, Suse Linux

X11 Forwarding using Xming and PuTTY

17 de agosto de 2016 8 Comentários

We can run graphical programs on Linux machines on campus remotely and display them on your desktop computer running Windows. We can do this by using running two applications together on your Windows machine: Xming and PuTTY.

What is Xming?

Xming is a PC X Window Server. This enables programs being run remotely to be displayed on your desktop. Download and run the installation program from: http://sourceforge.net/projects/xming/

1- Navigate to the Files section and download:
*Xming setup from the Xming folder
*The fonts package installer from the Xming-fonts folder

2- By default both programs will be installed into the same location, so don’t the worry about over writing files. We cannot work without both packages.
3- Once installed, running All Programs > Xming > XLaunch is a good idea to see what the configuration looks like. In most cases, the default options should be just fine.
4-Finally run All Programs > Xming > Xming to start the PC X Server. The “X” icon should be visible on the Windows Taskbar, as in the image below. The X Server must be started before setting up a SSH connection to a campus machine.

What is PuTTY?

PuTTY is a free SSH client. Through PuTTY we connect to a remote machine on the UT Dallas campus. Download the single Windows executable file from: http://www.chiark.greenend.org.uk/~sgtatham/putty/download.html There is no setup required, you can run by simply double clicking putty.exe.

Configuring PuTTY

1-Under Session, enter the hostname you want to connect to: 192.168.0.22 on port 22. Make sure the connection type is ssh.

putty11

1-Next, scroll to Connection > SSH > X11. Check the box next to Enable X11 Forwarding. The remote authentication should be set to MIT-Magic-Cookie-1

2-Finally go back to Session. You can save your session too, and load it each time you want to connect.

3-Click Open to bring up the terminal and login using your netid/password .

puttyx11

Now with the ready configuration, will connect to the server.

Note: At this point it is important to log in with the User that will run the graphical interface.

display1

Run the program

oracle

That is all.
Any doubts I am available.

CentOS 7, Linux, RedHat 7

Join Centos in Windows Active Directory

18 de julho de 2016 Nenhum comentário

This example shows to configure on the environment below.

Domain Server   : Windows Server 2012 R2
Domain Name    : poli01dc01
Realm                   : poli01ad01.local
Hostname            : poli01srv01.poli01ad01.local

Install some required packages.

yum -y install realmd sssd oddjob oddjob-mkhomedir adcli samba-common

Join in Windows Active Directory Domain.

# change the DNS to AD's one

[root@dlp ~]# nmcli c modify ens3 ipv4.dns 10.1.1.5

[root@dlp ~]# nmcli c down ens3; nmcli c up ens3
Connection successfully activated (D-Bus active path: /org/freedesktop/NetworkManager/ActiveConnection/1)

# discover Active Directory domain
[root@dlp ~]# realm discover POLI01AD01.LOCAL

srv.world
type: kerberos
realm-name: POLI01AD01.LOCAL
domain-name: POLI01AD01.LOCAL
configured: no
server-software: active-directory
client-software: sssd
required-package: oddjob
required-package: oddjob-mkhomedir
required-package: sssd
required-package: adcli
required-package: samba-common

# join in Active Directory domain
[root@dlp ~]# realm join POLI01AD01.LOCAL
Password for Administrator:
# AD's Administrator password

# make sure it's possible to get an AD user info or not
[root@dlp ~]# id poli01srv01.poli01ad01.local\\Serverworld
uid=406801001(POLI01SRV01@POLI01AD01.LOCAL) gid=406800513(domain users@srv.world) groups=406800513(domain users@srv.world)

# make sure it's possible to switch to an AD user or not
[root@dlp ~]# su - poli01srv01.poli01ad01.local\\Serverworld
Creating home directory for serverworld@srv.world.
[serverworld@srv.world@dlp ~]$     # just switched

If you’d like to omit domain name for AD user, configure like follows.

[root@dlp ~]# vi /etc/sssd/sssd.conf
# line 16: change

use_fully_qualified_names = False
[root@dlp ~]# systemctl restart sssd

[root@dlp ~]# id Administrator
uid=406800500(administrator) gid=406800513(domain users) groups=406800513(domain users),
406800572(denied rodc password replication group),406800518(schema admins),
406800520(group policy creator owners),406800512(domain admins),406800519(enterprise admins)

That is all

CentOS 7, Linux, RedHat 7

How to add New Disk in Linux CentOS 7 Without Rebooting

22 de junho de 2016 1 comentário

Increasing disk spaces on the Linux servers is a daily routine work for very system administrator. So, in this article we are going to show you some simple simple steps that you can use to increase your disk spaces on Linux CentOS 7 without rebooting to your production server using Linux commands. We will cover multiple methods and possibilities to increase and add new disks to the Linux systems, so that you can follow the one that you feel comfortable while using according to your requirements.

1) Increasing Disk of VM Guest:

Before increasing the disk volume inside your Linux system, you need to add a new disk or increase the one its has already attached with the system by editing its settings from your VMware vShere, Workstation or any other infrastructure environment that you are using.

2) Check Disk Space:

Run the following command to check the current size of your disk space.

# df -h

and

# fdisk -l

Here we can see that the total disk size is still the same that is 10 GB while we have already increased it to 50 GB from the back end.

3) Expanding Space without Rebooting VM

Now run the following commands to expand the disk space in the physical volume of the Operating System without rebooting the virtual machine by Re-scanning the SCSI Bus and then adding SCSI Device.

# ls /sys/class/scsi_host/

# echo "- - -" > /sys/class/scsi_host/host0/scan

# echo "- - -" > /sys/class/scsi_host/host1/scan

# echo "- - -" > /sys/class/scsi_host/host2/scan

Check the names of your SCSI devices and then rescan the SCSI buses using below commands.

# ls /sys/class/scsi_device/

# echo 1 > /sys/class/scsi_device/0\:0\:0\:0/device/rescan

# echo 1 > /sys/class/scsi_device/2\:0\:0\:0/device/rescan

That will rescan the current scsi bus and the disk size that we increased from the VM guest settings will be show up as you can see in the below image.

4) New Disk Partition:

Once you are able to see the increased disk space inside your system then the run the following command to format your disk for creating a new partition by following the steps to increase your physical disk volume.

# fdisk /dev/sda

result:

Welcome to fdisk (util-linux 2.23.2) press the 'm' key for help
Command (m for help): m
Command action
a toggle a bootable flag
b edit bsd disklabel
c toggle the dos compatibility flag
d delete a partition
g create a new empty GPT partition table
G create an IRIX (SGI) partition table
l list known partition types
m print this menu
n add a new partition
o create a new empty DOS partition table
p print the partition table
q quit without saving changes
s create a new empty Sun disklabel
t change a partition's system id
u change display/entry units
v verify the partition table
w write table to disk and exit
x extra functionality (experts only)

Command (m for help):

Type the ‘p’ to print the current partition table then create a new primary partition by typing the ‘n’ key and selecting the available sectors. Change the disk type to ‘Linux LVM’ by using ‘t’ command and selecting the code to ‘8e’ or leave as it to its default type that is ’83’.

Now write the table to disk and exit by Entring ‘w’ key as shown.

Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.

WARNING: Re-reading the partition table failed with error 16: Device or resource busy.
The kernel still uses the old table. The new table will be used at
the next reboot or after you run partprobe(8) or kpartx(8)

5)Creating Physical Volume:

As indicated above run the ‘partprobe’ or kpartx command so that the tables are ready to use and then create the new Physical Volume using the below commands.

# partprobe

# pvcreate /dev/sda3

To check the newly created volume run the following command to see if the new physical volume has been created and visible. After that we will extend the Volume Group ‘centos’ with the newly create Physical Volume as shown.

# pvdisplay

# vgextend centos /dev/sda3

6) Extending Logical Volume:

Now we will extend the Logical Volume to increase the disk space on it using the the below command.

# lvextend -L +40G /dev/mapper/centos-root

Once you get the successfully increased message, run the command as shown below to extend the size of your logical volume .

# xfs_growfs /dev/mapper/centos-root

The size of the ‘/’ partition has been increased successfully, you can check the size of your disk drives by using the ‘df’ command as shown.

7) Extending Root Partition by Adding New Disk Without Reboot:

This is the second method with but with quite similar commands to increase the size of the Logical volume in CentOS 7.

So, the first step is to Open the setting of your VM guest settings and click on the ‘Add’ new button and proceed to the next option.

Choose the required configuration for the new disk by selecting the size of the new disk and its type as shown in the below image.

Then come to the server side and repeat the following commands to scan your disk devices to the new disk is visible on the system.

# echo "- - -" > /sys/class/scsi_host/host0/scan

# echo "- - -" > /sys/class/scsi_host/host1/scan

# echo "- - -" > /sys/class/scsi_host/host2/scan

List the names of your SCSi devices

# ls /sys/class/scsi_device/

# echo 1 > /sys/class/scsi_device/1\:0\:0\:0/device/rescan
# echo 1 > /sys/class/scsi_device/2\:0\:0\:0/device/rescan
# echo 1 > /sys/class/scsi_device/3\:0\:0\:0/device/rescan

# fdisk -l

Once the new disk is visible run the below commands to create the new physical volume and add it to the volume group as shown.

# pvcreate /dev/sdb

# vgextend centos /dev/sdb

# vgdisplay

Now extend the Logical Volume by adding the disk space on it and then add it to the root partition.

# lvextend -L +20G /dev/mapper/centos-root

# xfs_growfs /dev/mapper/centos-root

# df -h

Conclusion:

Managing disk partitions in Linux CentOS 7 is a simple process to increase the disk space of any of your logical volumes by using the steps as described in this article. You don’t need to give your production server’s reboot for this purpose but simply rescan your SCSi devices and expand your desired LVM.

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