Set the hostname, time zone and time sync on a Linux server

Two small settings cause surprisingly many problems when they are wrong: the hostname (mail servers greet each other with it, many tools write it into logs) and the clock (certificates, package repositories, two-factor codes and log timelines depend on it). This guide sets both on Ubuntu, Debian, AlmaLinux and Rocky Linux.

Before you start

• You are connected over SSH as a user with sudo; see connect to your Linux server.
• The server already has a name from the order form; see configure a server in the order form. Change it only if you want your own name, for example one under your domain.
• For your own name, create an A record (and an AAAA record for IPv6) for it at your DNS host; see point a domain to your server.

Step 1: Check the current settings

hostnamectl
timedatectl

hostnamectl shows the Static hostname; timedatectl shows the local time, the Time zone, whether the System clock synchronized is yes and whether the NTP service is active.

Step 2: Set the hostname

Set the name in one step; hostnamectl hostname updates the static, transient and pretty names together:

sudo hostnamectl hostname srv1.example.com

Hostnames follow DNS rules: letters, digits and hyphens, labels separated by dots, at most 64 characters.

Then make the name resolvable on the server itself. Open /etc/hosts with sudo nano /etc/hosts and make sure there is one line with the server's public IP address, the full name and the short name. Debian's reference manual recommends the permanent IP address for servers that have one, instead of the 127.0.1.1 line used on workstations:

127.0.0.1       localhost
203.0.113.10    srv1.example.com srv1

If a line with 127.0.1.1 and the old name exists, remove it or change it to the new name.

Verify: hostname -f prints srv1.example.com, and getent hosts srv1.example.com returns your IP address.

Step 3: Set the time zone

List the names and set the one you want. Etc/UTC is a common choice for servers:

timedatectl list-timezones | grep -i europe
sudo timedatectl set-timezone Europe/Istanbul

Verify: timedatectl shows the new Time zone, and date prints the local time. Services that were already running may keep the old zone in their logs until they restart.

Step 4: Make sure the clock is synchronised

Linux uses one of two time services. Since Ubuntu 25.10, including Ubuntu 26.04 LTS, the default is chrony; Ubuntu 24.04 LTS uses systemd-timesyncd, and AlmaLinux and Rocky Linux use chrony. See which one runs on your server:

systemctl status chrony chronyd systemd-timesyncd --no-pager

Turn synchronisation on (it usually already is) and check it:

sudo timedatectl set-ntp true
timedatectl

With chrony, look at the details:

chronyc tracking
chronyc sources -v

With systemd-timesyncd:

timedatectl timesync-status

Verify: timedatectl shows System clock synchronized: yes. With chrony, Leap status in chronyc tracking is Normal and chronyc sources marks one source with * (the one in use).

If neither service is installed, install one: sudo apt install chrony on Ubuntu and Debian, sudo dnf install chrony and sudo systemctl enable --now chronyd on AlmaLinux and Rocky Linux. Run only one time service at a time.

Troubleshooting

sudo: unable to resolve host srv1.example.com. The new name is not in /etc/hosts. Add it as in Step 2; the warning disappears at once.

System clock synchronized: no for a long time. The server cannot reach its time servers. Outbound NTP uses UDP port 123: check that your firewall allows outgoing traffic (UFW allows it by default), then restart the service with sudo systemctl restart chrony (Ubuntu and Debian), chronyd (AlmaLinux and Rocky Linux) or systemd-timesyncd.

apt reports Release file … is not valid yet. The clock is behind. Fix synchronisation as in Step 4, then run sudo apt update again; see fix apt and dpkg errors.

The clock is far off and chrony corrects it only slowly. chrony adjusts large offsets gradually. To step the clock at once, run sudo chronyc makestep.

Mail is rejected with HELO or hostname errors. Receiving servers compare your hostname with your reverse DNS. Use the same fully qualified name in both; see reverse DNS (PTR).

Next steps

• Finish the basics: secure a new Linux server.
• Running a mail server? Set reverse DNS (PTR) to the same name.