coveralls: 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/bin/coveralls - from package: ruby-coveralls

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

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