atq: 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/atq - from package: at

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

On Debian possible default full paths are:

/usr/bin/atq - from package: at

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

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