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24 Jun 2015 Mount Samba share using gvfs-mount as normal user

This is just a shot note on how to mount a Samba or Windows CIFS share as a normal linux user using the gvfs-mount command in Centos 7 or RedHat 7.

Mounting a mountpoint share using the username user and password
[user@host] gvfs-mount smb://username@192.168.0.200/shared-folder

If the command finishes without any errors you can now access your smb mount on the following path

[user@host] ls -l /run/user/1000/gvfs/smb-share\:server\=192.168.0.200\,share\=shared-folder\,user\=username/

1000 corresponds to your users id and can be determined by the id command

[user@host] id
uid=1000(username) gid=1000(username) groups=1000(username)

PS
I compared the performance between connecting directly to a Samba share using UNC path and using gvfs-mount and saw that there is a noticeable speed decrease using gvfs-mount.
But if you have old software that does not support UNC path, then gvfs-mount is a good alternative to no access.

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26 May 2015 Installing Open vSwitch on CentOS 7

This post describes how to install the most recent version of Open vSwitch (ovs) on CentOS 7 and might be the base for future posts about using KVM as virtualization platform.

openvswitch-diagramOpen vSwitch is a production quality open source software switch designed to be used as a vswitch in virtualized server environments. A vswitch forwards traffic between different VMs on the same physical host and also forwards traffic between VMs and the physical network.

Install the needed packages (as root user)

# yum -y install wget openssl-devel kernel-devel

Install development tools

# yum groupinstall "Development Tools"

Add a ovswitch user

# adduser ovswitch

Download and unpack the openvswitch source code (as ovswitch user)

$ su - ovswitch
$ mkdir -p ~/rpmbuild/SOURCES
$ cd ~/rpmbuild/SOURCES
$ wget http://openvswitch.org/releases/openvswitch-2.3.1.tar.gz
$ tar xfz openvswitch-2.3.1.tar.gz

We will modify the openvswitch spec-file and use the kernel module CentOS provides instead of creating a new one.

$ sed 's/openvswitch-kmod, //g' openvswitch-2.3.1/rhel/openvswitch.spec > openvswitch-2.3.1/rhel/openvswitch_no_kmod.spec

Create a RPM-file to ease future package operations like upgrade

$ rpmbuild -bb --nocheck ~/openvswitch-2.3.1/rhel/openvswitch_no_kmod.spec
$ exit

Now is the time to install the RPM-package (as root)

# yum localinstall /home/ovswitch/rpmbuild/RPMS/x86_64/openvswitch-2.3.1-1.x86_64.rpm

If you have not disabled SElinux then you will see the following SELinux issues when you try to start the openvswitch service

install: cannot change owner and permissions of ‘/etc/openvswitch': No such file or directory and Creating empty database /etc/openvswitch/conf.db ovsdb-tool: I/O error: /etc/openvswitch/conf.db: failed to lock lockfile (No such file or directory)

This is one way to fix this issue

# mkdir /etc/openvswitch
# semanage fcontext -a -t openvswitch_rw_t "/etc/openvswitch(/.*)?"
# restorecon -Rv /etc/openvswitch

We are now ready to start the openvswitch service

# service openvswitch start
# chkconfig openvswitch on

Verify that we have installed openvswitch and that it is available

# virsh version
Compiled against library: libvirt 1.2.8
Using library: libvirt 1.2.8
Using API: QEMU 1.2.8
Running hypervisor: QEMU 1.5.3
# lsmod |grep openvswitch
openvswitch            70611  0 
gre                    13796  1 openvswitch
vxlan                  37409  1 openvswitch
libcrc32c              12644  2 xfs,openvswitch
# ovs-vsctl show
...
    Bridge "ovsbr1"
        Port "ovsbr1"
            Interface "ovsbr1"
                type: internal
    Bridge "ovsbr0"
        Port "enp0s25"
            Interface "enp0s25"
        Port "ovsbr0"
            Interface "ovsbr0"
                type: internal
    ovs_version: "2.3.1"

We are now ready to create a network bridge, but that will (maybe) be described in a future post of mine.

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25 May 2015 Generate a GRUB configuration file

It is sometimes needed to create a new, modify og recreate the grub configuration file.
One easy tool to regenerate the config file is the command grub2-mkconfig.
This command has helped me add a grub Windows startup option after installing CentOS 7.

Write the output of the command to console

# grub2-mkconfig

Write a new grub config file, overwriting the existing file

# grub2-mkconfig -o /boot/grub2/grub.cfg

This has been tested on CentOS 7 / RHEL 7.

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12 Nov 2014 Replace firewalld with iptables in CentOS 7

This is a short HOWTO replace or disable firewalld with iptables in CentOS 7.

Install iptables service
# yum -y install iptables-services

If you would like to save the firewall rules you need to run the following command
# iptables-save > iptables-rules.txt

These rules can be added to /etc/sysconfig/iptables but I usually use the rules that come with iptables package and add my rules to better suit my needs.

# systemctl enable iptables
# systemctl enable ip6tables

Stop firewalld
# systemctl stop firewalld

Disable firewalld
# systemctl disable firewalld

Start iptables service
# systemctl start iptables
# systemctl start ip6tables

And thats it.

Note
Always make sure that you are not locking yourself out of your server when starting the iptables firewall.

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28 Oct 2014 Change default grub startup in CentOS 7

This post describes how to change the default startup choice while booting up CentOS 7.

Edit the file /etc/default/grub

Change the line
GRUB_DEFAULT=saved
to
GRUB_DEFAULT="Windows 7 (loader) (on /dev/sda1)"

The value to add is determined by looking at the menuentry lines in /boot/grub2/grub.cfg
Choose the menuentry that you would like to be default.

To make this change active run the command
# grub2-mkconfig -o /boot/grub2/grub.cfg

You will see this change the next time you reboot.

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