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Solved: ChangeHostname

HowToChangeHostname

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Rename a computer

This page explains how to change a system's hostname (i.e. rename a computer/server)

Executive summary: hostname(1) isn't enough.

Contents

Rename a computer
    Core networking
        systemd
    Application specific
        avahi
        CUPS
        ejabberd
        Exim
        Mailname
        Message Of The Day
        OpenSSH server
        Self-signed SSL certificate
        ssmtp
        sysklogd
        fail2ban
        lvm
        md
    Idea of script to help you on
        Intrusive script
        Improved intrusive script
        Not-so intrusive script
    See also

Core networking

Update /etc/hostname

Update /etc/hosts, so local address(es) resolves with the new system name.
Reload the network configuration. You have two options:
    Reload configuration files

    <!> This will temporarily disconnect your system from the network (ssh usually resists short disconnection)

    <!> This might definitively disconnect your system from the network because networking might not restore connections; please reboot, which is not lazy, but ensures that your setup is really correct

    invoke-rc.d hostname.sh start
    invoke-rc.d networking force-reload
    invoke-rc.d network-manager force-reload

    ToDo: is it useful to reload network-manager?

    or the lazy way: Restart the system.

systemd

Versions of Debian with systemd installed can use "hostnamectl set-hostname mymachine". This tool depends on dbus so be sure to install that first.

Application specific

avahi

Avahi is used to publish (announce) local services. If you tweaked /etc/avahi/* you should run:

invoke-rc.d avahi-daemon force-reload

CUPS

CUPS is the Common Unix Printing System.

Adjust the /etc/printcap file.

You'll want to change the old hostname in any lines like this, hostname in bold: Kyocera_TASKalfa_3050ci|Kyocera TASKalfa 3050ci:rm=debian:rp=Kyocera_TASKalfa_3050ci: You'll need to restart the service for changes to take effect.

ejabberd

Refer to the Change Computer Hostname section of the ejabberd documentation website.

Exim

Reconfigure Exim (this adjusts /etc/exim4/update-exim4.conf.conf and /etc/mailname):

dpkg-reconfigure exim4-config

Or adjust manually /etc/exim4/update-exim4.conf.conf (hostname=). You need to restart the service.

Mailname

Reconfigure Exim (see above) or adjust manually /etc/mailname. You don't need to restart the service.

Message Of The Day

Adjust /etc/motd. You don't need to restart a service.

OpenSSH server

Adjust /etc/ssh/ssh_host_rsa_key.pub, /etc/ssh/ssh_host_dsa_key.pub, /etc/ssh/ssh_host_ed25519_key.pub and /etc/ssh/ssh_host_ecdsa_key.pub (root@hostname at the end). You need to restart the service.

Self-signed SSL certificate

Recreate the self-signed certificate created by the ssl-cert package using the hostname currently configured on your computer.

make-ssl-cert generate-default-snakeoil --force-overwrite

You need to restart the services using it, e.g. apache2.

ssmtp

Ssmtp is a light weight, send-only SMTP server.

Adjust /etc/ssmtp/ssmtp.conf (hostname=, etc.). You don't need to restart the service.

sysklogd

In order to make new hostname appear on syslog you should restart sysklogd service

fail2ban

fail2ban scan logs to detect connection failures and can ban IP on too many failures.

The hostname may be in the sender mail address in /etc/fail2ban/jail.local. You need to reload the service.

lvm

Logical Volume Manager (LVM) is a device mapper target that provides logical volume management.

Hostname appears in the backup configuration file /etc/lvm/backup/.

md

On a system that is using md on the root device boot will fail once update-initramfs -u is run if the hostname in /etc/mdadm/mdadm.conf does not match the hostname in the superblocks of the array members.

To change the hostname in the superblocks at the (initramfs) _ prompt (or from rescue media):

mdadm -A /dev/md/0 --update=name --name=new_hostname:0 /dev/sd[ab]1 # use YOUR devices

The md device must be down to be renamed.

Best reference: https://lists.debian.org/debian-arm/2016/02/msg00072.html

Idea of script to help you on

Intrusive script

Please understand that this script is dangerous. You should check if all the files listed by grep -rl "$old" /etc must really be modified before launching this script: Toggle line numbers

1 #!/bin/bash 2 # 3 usage() { 4 echo "usage : $0 " 5 exit 1 6 } 7 8 [ "1" ] || usage 9 10 old=(hostname) 11 new=1 12 13 grep "old" /etc/ -rl 2>/dev/null | 14 while read file 15 do 16 sed "s:old:new:g" "file" > "file.tmp" 17 mv -f "file.tmp" "file" 18 done

Take care you'd better do a grep before...

Improved intrusive script

This script will do the same stuff like the one above but it will ask you with a shell dialog which files you want modify before editing them. Toggle line numbers

1 #!/bin/bash 2 # 3 4 # Fetching new and old hostname 5 OLD_HOSTNAME=$(hostname) 6 NEW_HOSTNAME=1 7 8 WHIPTAIL_TITLE="Changing hostname" 9 WHIPTAIL_BACKTITLE="ShrimpDev <dev@csoellinger.at>" 10 WHIPTAIL_TEXT="Below you will find a checklist with all files where we found your old hostname \"{OLD_HOSTNAME}" inside /etc\n\nPlease check which files we should update to your new hostname "${NEW_HOSTNAME}"" 11 12 not_root() { 13 echo "ERROR: You have to be root to execute this script" 14 exit 1 15 } 16 17 usage() { 18 echo "usage : $0 [Optional:--backup/Set backup mode on] [Optional:--debug/Set debug mode on]" 19 exit 1 20 } 21 22 # Check if user is root 23 [ $EUID != 0 ] && not_root 24 25 # Check if we have at least one parameter 26 [ "$1" ] || usage 27 28 [ "$1" == "--backup" ] && usage 29 [ "$1" == "--debug" ] && usage 30 31 DEBUG="NO" 32 BACKUP="NO" 33 34 if [ "$2" == "--debug" ] || [ "$3" == "--debug" ]; then 35 DEBUG="YES" 36 fi 37 38 if [ "$2" == "--backup" ] || [ "3" == "--backup" ]; then 39 BACKUP="YES" 40 fi 41 42 [ "DEBUG" == "YES" ] && echo "DEBUG (NO FILES WILL BE CHANGED)" 43 [ "BACKUP" == "YES" ] && echo "BACKUP MODE ON" 44 45 # Grep all possible targets 46 TARGETS=((grep "OLD_HOSTNAME" /etc/ -rl)) 47 let TARGETSLENGTH={#TARGETS[@]} 48 49 CHECKLIST=() 50 for ((i=0; i<{#TARGETS[@]}; i++)); do 51 CHECKLIST+=("{TARGETS[i]}" "" "ON") 52 done 53 54 CHECKLIST_RESULT=(whiptail --clear --fb --title "WHIPTAIL_TITLE" --backtitle "WHIPTAIL_BACKTITLE" --checklist "$WHIPTAIL_TEXT" 30 80 TARGETSLENGTH "{CHECKLIST[@]}" 3>&2 2>&1 1>&3) 55 CHECKLIST_RESULT=${CHECKLIST_RESULT//"/} 56 CHECKLIST_RESULT_ARR=(echo $CHECKLIST_RESULT | tr ' ' '\n') 57 58 clear 59 60 for CHECKLIST_ITEM in "{CHECKLIST_RESULT_ARR[@]}"; do 61 echo "sed \"s:{OLD_HOSTNAME}:{NEW_HOSTNAME}:g\" \"{CHECKLIST_ITEM}" > "{CHECKLIST_ITEM}.tmp\"" 62 [ "DEBUG" == "NO" ] && sed "s:OLD_HOSTNAME:NEW_HOSTNAME:g" "CHECKLIST_ITEM" > "CHECKLIST_ITEM.tmp" 63 64 if [ "2" == "--backup" ]; then 65 echo "cp \"{CHECKLIST_ITEM}" "{CHECKLIST_ITEM}.BCK\"" 66 [ "DEBUG" == "NO" ] && cp "CHECKLIST_ITEM" "CHECKLIST_ITEM.BCK" 67 fi 68 69 echo "mv -f "{CHECKLIST_ITEM}.tmp\" \"{CHECKLIST_ITEM}"" 70 [ "DEBUG" == "NO" ] && mv -f "CHECKLIST_ITEM.tmp" "$CHECKLIST_ITEM" 71 72 echo "" 73 done 74 75 exit 0

Not-so intrusive script

#!/bin/bash

usage() { echo "usage : $0 " exit 1 }

[ "$1" ] || usage

old=$(hostname) new=$1

for file in
/etc/exim4/update-exim4.conf.conf
/etc/printcap
/etc/hostname
/etc/hosts
/etc/ssh/ssh_host_rsa_key.pub
/etc/ssh/ssh_host_dsa_key.pub
/etc/motd
/etc/ssmtp/ssmtp.conf do [ -f file ] && sed -i.old -e "s:old:$new:g" $file done