abook: 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/abook - from package: abook

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

On Debian possible default full paths are:

/usr/bin/abook - from package: abook

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

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