compare-histos: 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
/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/compare-histos - from package: rivet

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