unireverse: 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/unireverse - from package: uniutils

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

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