unregister-common-lisp-implementation: 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/sbin/unregister-common-lisp-implementation - from package: common-lisp-controller

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

On Debian possible default full paths are:

/usr/sbin/unregister-common-lisp-implementation - from package: common-lisp-controller

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

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