autossh: 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/autossh - from package: autossh

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

On Debian possible default full paths are:

/usr/bin/autossh - from package: autossh

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

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