convertlinks: 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 Debian possible default full paths are:

/usr/share/circos/tools/convertlinks/bin/convertlinks - from package: circos-tools

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

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