openstack-generate-docbook: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/openstack-generate-docbook - from package: python-openstack-doc-tools

You may install the required package with command apt-get install {package}

Error in other languages:
openstack-generate-docbook: bevel nie gevind nie
openstack-generate-docbook: comandă negăsită
openstack-generate-docbook: comando não encontrado
openstack-generate-docbook: commande introuvable
openstack-generate-docbook: command not found
openstack-generate-docbook: käsku ei ole
openstack-generate-docbook: không tìm thấy lệnh
openstack-generate-docbook: komanda nerasta
openstack-generate-docbook: Kommando nicht gefunden.
openstack-generate-docbook: kommandot finns inte
openstack-generate-docbook: komut yok
openstack-generate-docbook: nie znaleziono polecenia
openstack-generate-docbook: níor aimsíodh an t-ordú
openstack-generate-docbook: no se encontró la orden
openstack-generate-docbook: no s'ha trobat l'ordre
openstack-generate-docbook: opdracht niet gevonden
openstack-generate-docbook: parancs nem található
openstack-generate-docbook: perintah tidak ditemukan
openstack-generate-docbook: príkaz nenájdený
openstack-generate-docbook: příkaz nenalezen
openstack-generate-docbook: команда не найдена
openstack-generate-docbook: командата не е открита
openstack-generate-docbook: 命令找不到
openstack-generate-docbook: コマンドが見つかりません