yaz-config: 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/yaz-config - from package: libyaz-devel

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

On Debian possible default full paths are:

/usr/bin/yaz-config - from package: libyaz4-dev

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

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