unsort: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH

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/unsort - from package: unsort

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