utils: add set_linux_hostname

Add set_linux_hostname function to redefine the hostname of a
Linux install by overwriting the contents of /etc/hostname

src/utils/postinstall.py

@@ -66,6 +66,25 @@ def set_windows_hostname(disk, partition, name):
         umount(mountpoint)
 
 
+def set_linux_hostname(disk, partition, name):
+    logging.info(f'Configuring hostname')
+
+    device = get_partition_device(disk, partition)
+    mountpoint = device.replace('dev', 'mnt')
+
+    if not mount_mkdir(device, mountpoint):
+        raise OgError(f'Unable to mount {device} into {mountpoint}')
+
+    try:
+        hostname_path = f'{mountpoint}/etc/hostname'
+        with open(hostname_path, 'w') as f:
+            f.write(name)
+    except OSError as e:
+        raise OgError(f'Unable to configure Linux hostname: {e}') from e
+    finally:
+        umount(mountpoint)
+
+
 def configure_os_custom(disk, partition):
     if not shutil.which('configureOsCustom'):
         raise OgError('configureOsCustom not found')
@@ -149,6 +168,9 @@ def install_grub(disk, partition):
 
 
 def configure_os_linux(disk, partition):
+    hostname = gethostname()
+    set_linux_hostname(disk, partition, hostname)
+
     configure_fstab(disk, partition)
 
     if is_uefi_supported():