yexpand: 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/yexpand - from package: patchy

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

On Debian possible default full paths are:

/usr/bin/yexpand - from package: nypatchy

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

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