Category: Linux

Configure OVH Failover IP in Ubuntu 20.04/22.04

To configure IP in Ubuntu Server 20.04 guest, create a file

vi /etc/netplan/50-netwrk.yaml

add the following content

network:
    version: 2
    ethernets:
        eth0:
            addresses:
                - YOUR_FO_IP_HERE/32
            nameservers:
                addresses:
                    - 1.1.1.1
                search: []
            optional: true
            routes:
                - to: 0.0.0.0/0
                  via: YOUR_GW_IP_HERE
                  on-link: true

example

root@easyengine:~# cat /etc/netplan/50-cloud-init.yaml
network:
    version: 2
    ethernets:
        eth0:
            addresses:
                - 164.132.150.95/32
            nameservers:
                addresses:
                    - 1.1.1.1
                search: []
            optional: true
            routes:
                - to: 0.0.0.0/0
                  via: 51.255.79.254
                  on-link: true
root@easyengine:~#

“on-link: true” is what makes it work. The “on-link: true” option is used to specify that a specific route should be considered “on-link.” This means that the route is directly reachable on the local network segment, and packets destined for that route should be sent directly to the network interface associated with that network segment, rather than being routed through a gateway.

Test network config using

netplan try

If everything works fine, you can apply the changes with

netplan apply

See OVH, netplan

December 21, 2020

Ubuntu Remap keys in the keyboard
Left Shift key on my keyboard started acting up. It some times work, some times it won’t. I never use the caps lock key on my kayboard, this is just above the shift key. So i decided to use this key as left shift key.

To re-assign key, you need to edit file /usr/share/X11/xkb/symbols/pc

Lets take a copy of the file before we edit it
```
cp /usr/share/X11/xkb/symbols/pc ~/pc-backup
```
Edit
```
sudo gedit /usr/share/X11/xkb/symbols/pc
```
Find the line
```
     key  {	[ Caps_Lock		]	};
```
This is on line 22

Replace with
```
     key  {	[ Shift_L		]	};
```
Now you need to restart X-Windows by pressing ALT+F2, then type r. You can also just reboot your computer for the new keymap to work. After restart, i can use Caps lock key as my Left Shift key.

If you want to disable left shift key, you can comment the line
```
    key  {	[ Shift_L		]	};
```
by adding // at beginning of the line.

See Ubuntu
December 21, 2020
Red Hat Killing CentOS Linux, Fight for CentOS clone

RedHat, parent company of CentOS Linux announce it will stop supporting CentOS 8, the latest version of CentOS. CentOS is build from the source code RHEL, making a free version of stable and well-tested enterprise ready RHEL Linux. CentOS 7 will keep getting security updates until it reaches End Of Life June 30th, 2024. For Red Hat, maintaining CentOS wont help with their business. Now they don’t need to maintain CentOS, this will force many users to pay for Red Hat Enterprise Linux (RHEL).

The new version of CentOS known as CentOS Stream is a rolling release. It will be used as a staging version of RHEL. Red Hat expect CentOS Stream to be stable and allow community participation as users will be able to contribute to CentOS Steam. With CentOS, community contribution was limited because it was a copy of RHEL.

CentOS is populary used in web hosting servers as cpanel only supposed RHEL based Linux. With death of CentOS 8, cpanel have announced they will accelerate investment in development efforts to support additional operating systems. cPanel will suport Ubuntu LTS and expect to deliver a production-ready version in late 2021. After Ubuntu LTS, they will look into supporting Debian. Ubuntu is very popular with Cloud Servers as it come with latest software compared to CentOS. With many developers already using Ubuntu on their Desktop, supporting Ubuntu is wise decision by cpanel.

With CentOS 8 unexpected demise, many users will be looking for alternative OS. This opens up market for next CentOS clone.

Rocky Linux

CentOS co-founder, Gregory Kurtzer announced he will be releasing his own Red Hat Enterprise Linux (RHEL) replacement Rocky Linux. No ETA on release date yet.

https://rockylinux.org

You can join discussion on their reddit.com/r/RockyLinux/

Project Lenix

Igor Seletskiy, CloudLinux CEO and founder said they will make their own RHEL patch to patch compatible Open Source Linux – Project Lenix.

CloudLinux is a CentOS based commerical Linux, that is popular amoung web hosting providers as it allow resource limit per user and user isolation with CageFS. They also have support for kernel update with out reboot.

CloudLinux will be investing more than a million dollar into Project Lenix. CentOS 8 users will be able to convert into Project Lenix or CloudLinux easily with out reboot. In the announcement Igor Seletskiy said “Red Hat’s announcement has left users looking for an alternative with all that CentOS provides and without the disruption of having to move to alternative distributions. We promise to dedicate the resources required to Project Lenix that will ensure impartiality and a not-for-profit community initiative. CloudLinux already has the assets, infrastructure, and experience to carry out the mission, and we promise to be open about the process of developing Project Lenix”.

See CentOS

December 17, 2020
Oracle Linux

How to Install MySQL 5.7 on Oracle Linux 7
How to Migrate CentOS to Oracle Linux
How to Install PHP 5.6 on Oracle Linux 7
Updating Kernel on Oracle Linux with Ksplice

December 15, 2020

Ubuntu Server 20.04 set static IP with netplan

First check if you have file

/etc/cloud/cloud.cfg.d/subiquity-disable-cloudinit-networking.cfg

If the file exists, make sure, you have the following content in it.

root@ubuntu:~# cat /etc/cloud/cloud.cfg.d/subiquity-disable-cloudinit-networking.cfg
network: {config: disabled}
root@ubuntu:~#

Edit

vi /etc/netplan/00-installer-config.yaml

Replace all content with

network:
    version: 2
    ethernets:
        eth0:
            addresses: [192.168.1.100/24]
            routes:
                - to: default
                  via: 192.168.1.1
            nameservers:
                addresses: [1.1.1.1, 8.8.8.8]

In the above cause 192.168.1.100 is your static IP address. 192.168.1.1 is the gateway. eth0 is the network interface name.

Older versions of netpan used gateway4 instead of routes.

            gateway4: 192.168.1.1

Now try the changes with

netplan try

If all is good, you can make changes permanent with

netplan apply

See IP

December 15, 2020

imunify360 find license details

To check if your imunify360 license is valid, run

imunify360-agent rstatus

Example

[root@ldb002 ~]# imunify360-agent rstatus
OK
[root@ldb002 ~]#

To get more details of imunify360 license installed on the server

imunify360-agent rstatus --json --verbose

Example

[root@ldb002 ~]# imunify360-agent rstatus --json --verbose
{
  "expiration": null,
  "id": "Imunify360-xxxxxxxx",
  "license": {
    "expiration": null,
    "id": "Imunify360-xxxxxxxx",
    "license_type": "imunify360",
    "message": "",
    "redirect_url": "",
    "status": true,
    "user_count": 5,
    "user_limit": 2147483647
  },
  "license_type": "imunify360",
  "message": "",
  "redirect_url": "",
  "status": true,
  "strategy": "CSF_COOP",
  "user_count": 5,
  "user_limit": 2147483647,
  "version": "5.3.3-1"
}
[root@ldb002 ~]#

December 14, 2020

supervisorctl
supervisorctl is used to control supervisord.

To reload all monitored processes, run
```
supervisorctl reload
```
To restart a monitored process, run
```
supervisorctl restart PROCESS_NAME_HERE
```
See supervisord
December 14, 2020

pvdisplay

pvdisplay is used to display all physical volumes on a LVM.

root@server12:~# pvdisplay
  --- Physical volume ---
  PV Name               /dev/sda3
  VG Name               vg
  PV Size               <9.51 GiB / not usable 0   
  Allocatable           yes (but full)
  PE Size               4.00 MiB
  Total PE              2434
  Free PE               0
  Allocated PE          2434
  PV UUID               VA8sp6-2zKJ-GGtJ-aWe5-cPlm-uTHu-oKpiua
   
  --- Physical volume ---
  PV Name               /dev/sda4
  VG Name               vg
  PV Size               30.00 GiB / not usable 4.98 MiB
  Allocatable           yes (but full)
  PE Size               4.00 MiB
  Total PE              7679
  Free PE               0
  Allocated PE          7679
  PV UUID               LjsCxR-J0lC-5z2P-Fqew-MXoG-59X3-B7dmDP
   
  --- Physical volume ---
  PV Name               /dev/sda5
  VG Name               vg
  PV Size               <40.00 GiB / not usable 3.98 MiB
  Allocatable           yes (but full)
  PE Size               4.00 MiB
  Total PE              10239
  Free PE               0
  Allocated PE          10239
  PV UUID               km0iBF-XakC-s9GF-hFnf-K1b0-4Hec-FAEcwp
   
root@server12:~#

See LVM

December 14, 2020

lvdisplay

lvdisplay is used to display logical volumes. You can also use lvs command.

root@server12:~# lvdisplay
  --- Logical volume ---
  LV Path                /dev/vg/lv_root
  LV Name                lv_root
  VG Name                vg
  LV UUID                aLjP9v-Cc6s-mxS6-kcKz-Fs4e-kW5c-Wuq009
  LV Write Access        read/write
  LV Creation host, time ubuntu-server, 2020-05-19 13:02:06 +0000
  LV Status              available
  # open                 1
  LV Size                78.99 GiB
  Current LE             20222
  Segments               3
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           253:0
   
  --- Logical volume ---
  LV Path                /dev/vg/lv_swap
  LV Name                lv_swap
  VG Name                vg
  LV UUID                es9Yvn-Tfh1-KO6L-7cAw-N1jg-9NAL-9hd3To
  LV Write Access        read/write
  LV Creation host, time ubuntu-server, 2020-05-19 13:02:07 +0000
  LV Status              available
  # open                 2
  LV Size                520.00 MiB
  Current LE             130
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           253:1
   
root@server12:~#

See LVM

December 14, 2020

CentOS 6 Invalid release/repo/arch combination

When i run yum update on a CentOS 6 server, i get error “Invalid release/repo/arch combination/”.

This error is due to CentOS reaching its End Of Life and no longer supported.

What you need to do is upgrade your server to the latest supported CentOS versions like CentOS 7 or CentOS 8. Converting to Oracle Linux 6 is another option, it is binary compatible with CentOS/RHEL 6, offers extended support until Jun 2024 and Indefinite Sustaining Support. If you want to convert CentOS 6 to Oracle Linux, see How to Migrate CentOS to Oracle Linux.

If you just need to fix the error, you need to go through each .repo file in the folder

/etc/yum.repos.d/

Comment out lines like

mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=os&infra=$infra

Replace it with centos 6 vault repo URL

baseurl=https://vault.centos.org/centos/$releasever/os/$basearch/

You can find modified yum repository files at

https://github.com/serverok/centos6-repo

You can replace your existing repository files inside /etc/yum.repos.d folder with files in the above git repository with following commands.

cd /etc
mv yum.repos.d yum.repos.d-old
git clone https://github.com/serverok/centos6-repo.git yum.repos.d

If you get git not found error, you may need to manually download files from the repo and place in the directory /etc/yum.repos.d/.

After this, you will be able to update your system. If you have any other repo installed, you can copy it from yum.repos.d-old folder to make it active again.

Here is the updated CentOS-Base.repo file

https://raw.githubusercontent.com/serverok/centos6-repo/main/CentOS-Base.repo

# CentOS-Base.repo
#
# The mirror system uses the connecting IP address of the client and the
# update status of each mirror to pick mirrors that are updated to and
# geographically close to the client.  You should use this for CentOS updates
# unless you are manually picking other mirrors.
#
# If the mirrorlist= does not work for you, as a fall back you can try the 
# remarked out baseurl= line instead.
#
#

[base]
name=CentOS-$releasever - Base
baseurl=https://vault.centos.org/centos/$releasever/os/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-6

#released updates 
[updates]
name=CentOS-$releasever - Updates
baseurl=https://vault.centos.org/centos/$releasever/updates/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-6

#additional packages that may be useful
[extras]
name=CentOS-$releasever - Extras
baseurl=https://vault.centos.org/centos/$releasever/extras/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-6

#additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-$releasever - Plus
baseurl=https://vault.centos.org/centos/$releasever/centosplus/$basearch/
gpgcheck=1
enabled=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-6

#contrib - packages by Centos Users
[contrib]
name=CentOS-$releasever - Contrib
baseurl=https://vault.centos.org/centos/$releasever/contrib/$basearch/
gpgcheck=1
enabled=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-6

After updating yum repo, run

yum clean all
yum makecache

December 13, 2020

Firewalld
firewall-cmd is used to manage firewall (iptables). It is used by default on latest version of CentOS, RHEL.
Check firewall status

To see if firewall is running of not use
```
firewall-cmd --state
```
or
```
systemctl status firewalld
```
To disable firewalls
```
systemctl stop firewalld
systemctl disable firewalld
```
Open a port in firewall

To allow HTTP and HTTPS traffic, run
```
firewall-cmd --permanent --zone=public --add-service=http
firewall-cmd --permanent --zone=public --add-service=https
firewall-cmd --permanent --zone=public --add-service=ssh
firewall-cmd --permanent --zone=public --add-port=25/tcp
firewall-cmd --reload
```
Permanent option make the changes permanant. You need to reload firewall after using –permanent. If you want to open a port in current session and make it permanant, run the command with and with out –permanent.

Open a port range in firewall
```
firewall-cmd --zone=public --add-port=22-65535/tcp
```
Close a port in firewall

To close a port, you can use command same as you open with –add replaced with –remove.
```
firewall-cmd --permanent --zone=public --remove-service http
firewall-cmd --permanent --zone=public --remove-port 25/tcp
```
Whitelist an IP address
```
firewall-cmd --zone=trusted --add-source=IP_ADDR_HERE
```
To remove an IP, use
```
firewall-cmd --zone=trusted --remove-source=IP_ADDR_HERE
```
Firewalld Zones

Zone is a collection of rules that can be applied to a specific interface. Some useful commands are
```
firewall-cmd --get-active-zones
firewall-cmd --get-default-zone
firewall-cmd --list-all-zones
firewall-cmd --info-zone=public
```
Zones are stored in /usr/lib/firewalld/zones

Services

Services are pre-made rules for a specific application. Some useful commands are
```
firewall-cmd --get-services
firewall-cmd --info-service SERVICE_NAME_HERE
```
Services are stoed in /usr/lib/firewalld/services/ or /etc/firewalld/services/.

Save run time configuration into permanant
```
firewall-cmd --runtime-to-permanent
```
iptables

See firewall
December 6, 2020
Firewalld list all open ports
To list all open ports in firealld, run
```
firewall-cmd --list-ports
```
You may need to also use
```
[root@oc1 ~]# firewall-cmd --list-services
http https ssh
[root@oc1 ~]# 
```
Example

See firewalld
December 6, 2020

Category: Linux

Rocky Linux

Project Lenix

Check firewall status

Open a port in firewall

Open a port range in firewall

Close a port in firewall

Whitelist an IP address

Firewalld Zones

Services

Save run time configuration into permanant