install-docs: 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 Debian possible default full paths are:

/usr/sbin/install-docs - from package: doc-base

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

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