sh: 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:

/bin/sh - from package: bash

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

On Debian possible default full paths are:

/bin/sh - from package: dash

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

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