18 Sep 2018 Reinstall grub using Live-CDROM
After a failed upgrade to Ubuntu 14.04 the server complains about missing disk error. The solution was to reinstall grub and reboot. The procedure is loosely described here.
Boot your Ubuntu server using av Live CDROM you have downloaded from Ubuntu. Choose to Test Ubuntu since installation is not the desired option at this time.
Open a terminal window and become root using the sudo command and make the LVM disks available
# lvm vgscan -v
# vgchange -a y vgdisk-for-root-partition
# mkdir /mnt/rootMount
# mount /dev/vgdisk-for-root-partition/root /mnt/root
Create a chroot environment where you can run the grub-install command
# mount –bind /dev /mnt/root/bind
# mount –bind /proc /mnt/root/proc
# mount /boot /mnt/root/boot
# chroot /mnt/root /bin/bash
# grub-install –root /dev/sda
Always make sure you are working on the right disk before using the grub-install command since it overwrites the boot loader.
Reboot the server when the grub-install command has been successfully run. The server should now be rebooting and working again as it used to.
Tags: chroot, grub-install, lvm, mount, vgchange
Posted by Hans-Henry Jakobsen
17 Jul 2018 Install HAProxy 1.8 on CentOS 7
This is just a short write-up on installing HAProxy version 1.8 on CentOS 7 using Software Collections. HAProxy is an application layer (Layer 7) load balancing and high availability solution that you can use to implement a reverse proxy for HTTP and TCP-based Internet services. I am using it to expose my webservices through a reverse proxy.
If default HAProxy version 1.5 is installed then it should be removed because it is blocking the new version we are going to install.
# yum remove haproxy ... warning: /etc/haproxy/haproxy.cfg saved as /etc/haproxy/haproxy.cfg.rpmsave ...
This warning indicates that your old HAProxy config file is renamed. This is useful to know if you are planning to use the same file in HAProxy version 1.8.
Install the Software Collections (SCL) repository to get access to the new HAProxy version
# yum install centos-release-scl
Update your repositories and accept the new repository.
Installing HAProxy 1.8
# yum install rh-haproxy18-haproxy rh-haproxy18-haproxy-syspaths
The rh-haproxy18-haproxy-syspaths package is a system-wide wrapper for the rh-haproxy18-haproxy package and allows us to run HAProxy 1.8 as a service. This package conflicts with the HAProxy and cannot be installed on one system.
If we now look in /etc/haproxy/haproxy.cfg we will see that the config file is a symling to the new package
# ls -l /etc/haproxy/ lrwxrwxrwx. 1 root root 44 Jul 17 18:19 haproxy.cfg -> /etc/opt/rh/rh-haproxy18/haproxy/haproxy.cfg
If you had HAProxy 1.5 installed previously and would like to continue using the config file, copy it to the new location. First we preserve the original HAProxy 1.8 config file by renaming it or just copy the rules that you need from the old config.
# mv /etc/opt/rh/rh-haproxy18/haproxy/haproxy.cfg /etc/opt/rh/rh-haproxy18/haproxy/haproxy.cfg.original # cp /etc/haproxy/haproxy.cfg.rpmsave /etc/opt/rh/rh-haproxy18/haproxy/haproxy.cfg
We are now ready to start HAProxy 1.8 with our old config file
# systemctl start rh-haproxy18-haproxy # systemctl status rh-haproxy18-haproxy
If we would like to have the new HAProxy version to auto-start on reboot
# systemctl enable rh-haproxy18-haproxy
Done.
Installing HAProxy 1.8 on RedHat 7 is similar, except you use subscription-manager and add the software collections repository.
Tags: CentOS, haproxy, scl, software_collections
Posted by Hans-Henry Jakobsen
02 Mar 2018 Configure VLAN on top of network team using nmcli / NetworkManager
This post is almost similar as the previous where I created a team with two network nics as members using NetworkManager nmcli from a console. This time I have added a VLAN on top of my LACP network team with two member nics.
First we need to install the teamd package if it is not already installed.
# yum install teamd
Using the console command nmcli and NetworkManager and a json-config file with the default config for the team, filename team-master-conf.json:
{
"runner": {
"active": true,
"fast_rate": true,
"name": "lacp",
"tx_hash": [ "eth", "ipv4" ]
},
"tx_balancer": { "name": "basic" },
"link_watch": { "name": "ethtool" }
}
# nmcli con add type team con-name team0 ifname team0 config team-master-conf.json # nmcli con add type team-slave con-name team0-em1 ifname em1 master team0 # nmcli con add type team-slave con-name team0-em2 ifname em2 master team0
I have not added an IP-address to the new team since I will add that on the VLAN interface.
Check the status of the team
# nmcli con status NAME UUID TYPE DEVICE team0 7f0c0038-b8c1-45bb-a286-501d02304700 team team0 team0-em1 0394e2ae-6610-4997-92db-775876866d0d 802-3-ethernet em1 team0-em2 7050d641-83bb-497a-ae23-6af029386117 802-3-ethernet em2
Check the state of the team
# teamdctl team0 state
setup:
runner: lacp
ports:
em1
link watches:
link summary: up
instance[link_watch_0]:
name: ethtool
link: up
down count: 1
runner:
aggregator ID: 12, Selected
selected: yes
state: current
em2
link watches:
link summary: up
instance[link_watch_0]:
name: ethtool
link: up
down count: 0
runner:
aggregator ID: 12, Selected
selected: yes
state: current
runner:
active: yes
fast rate: yes
Add a VLAN to the network team
# nmcli con add type vlan con-name team0-vlan12 dev team0 id 12 ip4 10.1.0.20/24 gw4 10.1.0.1
The new config looks like this
# nmcli con s | grep team team0 7f0c0038-b8c1-45bb-a286-501d02304700 team team0 team0-vlan12 d5de0d83-d490-4535-915c-4cbdcf39830b vlan team0.12 team0-em1 0394e2ae-6610-4997-92db-775876866d0d 802-3-ethernet em1 team0-em2 7050d641-83bb-497a-ae23-6af029386117 802-3-ethernet em2
This config is confirmed working on RHEL 7.4 and Centos.
I assume the switch is configured as needed before starting this config on the server.
Tags: CentOS, lacp, nmcli, RedHat, rhel7, teamd, teamdctl, vlan
Posted by Hans-Henry Jakobsen
02 Mar 2018 Configure network team using nmcli / NetworkManager
This is a short post on how to create a LACP network team with two member nics using NetworkManager and nmcli. Configuring av network team is very similar to creating a bond.
First we need to install the teamd package if it is not already installed.
# yum install teamd
I have also included a json-config file with the default config for the team, filename team-master-conf.json:
{
"runner": {
"active": true,
"fast_rate": true,
"name": "lacp",
"tx_hash": [ "eth", "ipv4" ]
},
"tx_balancer": { "name": "basic" },
"link_watch": { "name": "ethtool" }
}
# nmcli con add type team con-name team0 ifname team0 config team-master-conf.json ip4 10.0.0.10/24 gw4 10.0.0.1 # nmcli con add type team-slave con-name team0-em1 ifname em1 master team0 # nmcli con add type team-slave con-name team0-em2 ifname em2 master team0
Check the status of the team
# nmcli con status NAME UUID TYPE DEVICE team0 7f0c0038-b8c1-45bb-a286-501d02304700 team team0 team0-em1 0394e2ae-6610-4997-92db-775876866d0d 802-3-ethernet em1 team0-em2 7050d641-83bb-497a-ae23-6af029386117 802-3-ethernet em2
Check the state of the team
# teamdctl team0 state
setup:
runner: lacp
ports:
em1
link watches:
link summary: up
instance[link_watch_0]:
name: ethtool
link: up
down count: 1
runner:
aggregator ID: 12, Selected
selected: yes
state: current
em2
link watches:
link summary: up
instance[link_watch_0]:
name: ethtool
link: up
down count: 0
runner:
aggregator ID: 12, Selected
selected: yes
state: current
runner:
active: yes
fast rate: yes
Some NetworkManager basics
Take down a network interface
# nmcli con down em1
Take up a network interface
# nmcli con up em1
Delete a network interface
# nmcli con delete em1
Add a new network device
# nmcli con add em1
This config is confirmed working on RHEL 7.4 and Centos.
I assume the switch is configured as needed before starting this config on the server.
Tags: CentOS, lacp, nmcli, RedHat, rhel7, teamd, teamdctl
Posted by Hans-Henry Jakobsen
12 Jan 2018 Exclude certain packages from yum-cron (but not from yum)
This is a solution for how you can exclude certain packages being updated when using yum-cron.
Docker and kernel are packages I would like to exclude from yum-cron.
The solution to this is to modify the /etc/yum/yum-cron.conf file adding this to the [base] section
RHEL7/Centos7
[base]
...
exclude = kernel* docker*
On RHEL6/Centos6 you can use the YUM_PARAMETER to do the same thing
YUM_PARAMETER=kernel* docker*
If you would like to exclude certain packages from yum alltogether you need to modify the affected yum repository.
Example to permanently exclude certain packages like Docker from being updated using the yum command/CLI
RHEL7
Modify /etc/yum.repos.d/redhat.repo
Add the following line under [rhel-7-server-extras-rpms]
exclude = docker*
Before adding a exclude command verify that you add the exclude line under the right repository.
Example
# yum info docker
…
From repo : rhel-7-server-extras-rpms
Tags: CentOS, docker, RedHat, rhel6, rhel7
Posted by Hans-Henry Jakobsen
