ical2vcal: 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:

/usr/bin/ical2vcal - from package: kdepim

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

On Debian possible default full paths are:

/usr/bin/ical2vcal - from package: korganizer

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

Error in other languages:
ical2vcal: bevel nie gevind nie
ical2vcal: comandă negăsită
ical2vcal: comando não encontrado
ical2vcal: commande introuvable
ical2vcal: command not found
ical2vcal: käsku ei ole
ical2vcal: không tìm thấy lệnh
ical2vcal: komanda nerasta
ical2vcal: Kommando nicht gefunden.
ical2vcal: kommandot finns inte
ical2vcal: komut yok
ical2vcal: nie znaleziono polecenia
ical2vcal: níor aimsíodh an t-ordú
ical2vcal: no se encontró la orden
ical2vcal: no s'ha trobat l'ordre
ical2vcal: opdracht niet gevonden
ical2vcal: parancs nem található
ical2vcal: perintah tidak ditemukan
ical2vcal: príkaz nenájdený
ical2vcal: příkaz nenalezen
ical2vcal: команда не найдена
ical2vcal: командата не е открита
ical2vcal: 命令找不到
ical2vcal: コマンドが見つかりません