update-alternatives: 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/update-alternatives - from package: chkconfig

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

On Debian possible default full paths are:

/usr/sbin/update-alternatives - from package: dpkg
/usr/bin/update-alternatives - from package: dpkg

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

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