fsfreeze: 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:

/sbin/fsfreeze - from package: util-linux-ng

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

On Debian possible default full paths are:

/sbin/fsfreeze - from package: util-linux

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

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