mosh: 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/mosh - from package: mosh

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

On Debian possible default full paths are:

/usr/bin/mosh - from package: mosh

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

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