0store-secure-add: 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 CentOS possible default full paths are:

/usr/bin/0store-secure-add - from package: zeroinstall-injector

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/0store-secure-add - from package: 0install-core

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

Error in other languages:
0store-secure-add: bevel nie gevind nie
0store-secure-add: comandă negăsită
0store-secure-add: comando não encontrado
0store-secure-add: commande introuvable
0store-secure-add: command not found
0store-secure-add: käsku ei ole
0store-secure-add: không tìm thấy lệnh
0store-secure-add: komanda nerasta
0store-secure-add: Kommando nicht gefunden.
0store-secure-add: kommandot finns inte
0store-secure-add: komut yok
0store-secure-add: nie znaleziono polecenia
0store-secure-add: níor aimsíodh an t-ordú
0store-secure-add: no se encontró la orden
0store-secure-add: no s'ha trobat l'ordre
0store-secure-add: opdracht niet gevonden
0store-secure-add: parancs nem található
0store-secure-add: perintah tidak ditemukan
0store-secure-add: príkaz nenájdený
0store-secure-add: příkaz nenalezen
0store-secure-add: команда не найдена
0store-secure-add: командата не е открита
0store-secure-add: 命令找不到
0store-secure-add: コマンドが見つかりません