rebuild-gcj-db: 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/rebuild-gcj-db - from package: libgcj-common

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