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This document is a WORK IN PROGRESS.
This is just a quick personal cheat sheet: treat its contents with caution!

OVH

OVH, is a French cloud computing company which offers VPS, dedicated servers and other web services.

This cheat sheet will focus on various tips related to some OVH services.

Reference(s)

Table of contents

DNS zone

See https://docs.ovh.com/gb/en/domains/web_hosting_how_to_edit_my_dns_zone/#dns-records to understand type of DNS record in the DNS zone.

DynHost

Note

DynHost is the name given by OVH to the service allowing to regularly update the IP address attributed to a domain name (for those who knows DynDNS, it corresponds to the same service offered by DynDNS). It is targeted for people who have an Internet subscription with dynamic IP addressing, wishing to access their computer network from outside or hosting any server to the Internet.

With DynHost, you can point a sub-domain to a dynamic IP address that will be updated in your associated OVH DNS each time it changes.

In order to update the DNS from your server, a simple script is needed:

  • As a first prerequisite, the bind* package will be needed (in order to get the dig tool):

Install dig

#emerge -a net-dns/bind-tools # for the `dig` tool

# pacman -S bind

# nix-env -iA nixos.bind

# nix-env -iA nixpkgs.bind

# apt install bind9

# yum install bind

# dnf install bind

  • As a second prerequisite, you need to create dedicated credentials associated to your OVH DynHost like describe here. Remember those credentials, they will be needed in the bellow script (LOGIN and PASSWORD variables).

  • Now, you can simply create the following script (don't forget to change the OVH_DYN_HOST, LOGIN and PASSWORD variables - inside the script - according to your needs): 

    $ sudo vi /opt/update-ovh-dyn-host-your-sub-domain.name.ovh
    > #!/bin/bash
    >
    > #⚠️ Prerequisites: bash, realpath, dig, curl, date
    >
    > OVH_DYN_HOST='your-sub-domain.name.ovh'
    > LOGIN='your-sub-domain-login'
    > PASSWORD='your-sub-domain-password'
    >
    > SCRIPT_LOC="$(realpath $0)"
    > PATH_LOG=/var/log/update-ovh-dyn-host-"$OVH_DYN_HOST".log
    >
    > OVH_DYN_HOST_IP=$(dig +short $OVH_DYN_HOST A)
    > CURRENT_IP=$(curl --ipv4 --silent --max-time 5 "ifconfig.io" 2>/dev/null)
    > CURRENT_DATETIME=$(date -R)
    >
    > valid_ipv4() {
    >     ip=$1
    >     if [[ $ip =~ ^[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}$ ]]
    >     then
    >         return 0
    >     else
    >         return 1
    >     fi
    > }
    >
    > if [[ -z $OVH_DYN_HOST_IP ]] || ! valid_ipv4 "$OVH_DYN_HOST_IP"
    > then
    >     echo "[$CURRENT_DATETIME] $SCRIPT_LOC: not updating $OVH_DYN_HOST OVH DynHost, because a wrong OVH DynHost IP has been retrieved!" >> $PATH_LOG
    >     return 1
    > fi
    >
    > if [[ -z $CURRENT_IP ]] || ! valid_ipv4 "$CURRENT_IP"
    > then
    >     echo "[$CURRENT_DATETIME] $SCRIPT_LOC: not updating $OVH_DYN_HOST OVH DynHost, because a wrong (current) host IP has been retrieved!" >> $PATH_LOG
    >     return 1
    > fi
    >
    > if [ "$OVH_DYN_HOST_IP" != "$CURRENT_IP" ]
    > then
    >     UPDATE_REQUEST=$(curl -m 5 -L --location-trusted --user "$LOGIN:$PASSWORD" "https://www.ovh.com/nic/update?system=dyndns&hostname=$OVH_DYN_HOST&myip=$CURRENT_IP")
    >     echo "[$CURRENT_DATETIME] $SCRIPT_LOC: updating $OVH_DYN_HOST OVH DynHost IPv4 from $OVH_DYN_HOST_IP to $CURRENT_IP - request result: $UPDATE_REQUEST" >> $PATH_LOG
    > else
    >     echo "[$CURRENT_DATETIME] $SCRIPT_LOC: no OVH DynHost update needed for $OVH_DYN_HOST !" >> /dev/null # this message doesn't need to be logged
    > fi

  • Make sure the script is executable and is owned by root: 

    $ sudo chmod +x /opt/update-ovh-dyn-host-your-sub-domain.name.ovh
$ sudo chown root:root /opt/update-ovh-dyn-host-your-sub-domain.name.ovh

  • Add it to the root user crontab (e.g. in order to run it every minute): 

    $ sudo crontab -e # run the script every minute
    > # * * * * *  command_or_script_to_execute
    > # - - - - -
    > # | | | | |
    > # | | | | +- day of week (0 - 7) (where sunday is 0 and 7)
    > # | | | +--- month (1 - 12)
    > # | | +----- day (1 - 31)
    > # | +------- hour (0 - 23)
    > # +--------- minute (0 - 59)
    > ...
    > */1 * * * * /opt//opt/update-ovh-dyn-host-your-sub-domain.name.ovh

Tip

If you still don't have cron installed, you might want to look at my cron cheat sheet.

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