ci: 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/ci - from package: rcs

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

On Debian possible default full paths are:

/usr/bin/ci - from package: rcs

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

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