yaz-illclient: 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-illclient - from package: yaz

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

On Debian possible default full paths are:

/usr/bin/yaz-illclient - from package: yaz-illclient

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

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