coq-tex: 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/coq-tex - from package: coq

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

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