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templates: ensure RHCOS node hostnames are mostly valid
This aims to fix all the edge-cases around invalid hostnames. This can include: - localhost as the hostname - a static hostname larger than 63 characters - slow reverse DNS host name discovery - truncated hostname in initramfs discovery that is 64 character long Previously, there was a node-valid-hostname.service, but it only ensured that the hostname was not localhost. When running in the initramfs, NetworkManager will truncate the hostname at 64 charcters resulting in the `node-valid-hostname.service` checks succeeding (!localhost) but still invalid for the cluster. This change consolides the logic used by the dispatcher script _and_ the systemd unit into a library script that is used by both. This fix is not ideal, but it seems like the best path that be backported to 4.3 and 4.5. Fixes BZs 1844613, 1845885, 1853400, 1853584 (and probably more) Signed-off-by: Ben Howard <[email protected]>
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Jul 9, 2020
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templates/common/_base/files/usr-local-sbin-set-valid-hostname.yaml
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,83 @@ | ||
| mode: 0755 | ||
| path: "/usr/local/sbin/set-valid-hostname.sh" | ||
| contents: | ||
| inline: | | ||
| #!/bin/bash | ||
| # On some platforms the hostname may be too long (>63 chars). | ||
| # - On firstboot the hostname is set in the initramfs before NetworkManager | ||
| # And it may be truncated at 64 characters (too long) | ||
| # - On reboot affect nodes use 'localhost'. | ||
| # | ||
| # This script is a simple workaround for hostname woes, including | ||
| # - NOT a localhost name | ||
| # - NOT longer than 63 characters. Names will be truncated at the | ||
| # first dot, and then capped at 63 char (which ever is less). | ||
| # - Race conditions between truncated hostnames by the dhclient | ||
| # and NetworkManager. | ||
| # | ||
| # Finally, this script is invoked via: | ||
| # - /etc/NetworkManager/dispatcher.d/90-long-hostnames | ||
| # - on boot via node-valid-hostname.service | ||
| export PATH="/usr/bin:/usr/local/bin:/sbin:/usr/local/sbin:/bin:${PATH}" | ||
| log() { logger --tag "$(basename $0)" "${@}"; } | ||
| # wait_localhost waits until the host gets a real hostname. | ||
| # This will wait indefinately. node-valid-hostname.service will terminate | ||
| # this after 5m. | ||
| wait_localhost() { | ||
| log "waiting for non-localhost hostname to be assigned" | ||
| while [[ "$(< /proc/sys/kernel/hostname)" =~ (localhost|localhost.localdomain) ]]; | ||
| do | ||
| sleep 1 | ||
| done | ||
| log "node identified as $(</proc/sys/kernel/hostname)" | ||
| exit 0 | ||
| } | ||
| set_valid_hostname() { | ||
| local host_name=${1} | ||
| local type_arg="transient" | ||
| # /etc/hostname is used for static hostnames and is authorative. | ||
| # This will check to make sure that the static hostname is the | ||
| # less than or equal to 63 characters in length. | ||
| if [ -f /etc/hostname ] && [ "$(cat /etc/hostname | wc -m)" -gt 0 ]; then | ||
| etc_name="$(< /etc/hostname)" | ||
| type_arg="static" | ||
| if [ "${etc_name}" != "${host_name}" ]; then | ||
| log "/etc/hostname is set to ${etc_name} but does not match ${host_name}" | ||
| log "using /etc/hostname as the authorative name" | ||
| host_name="${etc_name}" | ||
| fi | ||
| fi | ||
| # Only mutate the hostname if the length is longer than 63 characters. The | ||
| # hostname will be the lesser of 63 characters after the first dot in the | ||
| # FQDN. | ||
| if [ "${#host_name}" -gt 63 ]; then | ||
| alt_name=$(printf "${host_name}" | cut -f1 -d'.' | cut -c -63) | ||
| log "${host_name} is longer than 63 characters, using trunacated hostname" | ||
| host_name="${alt_name}" | ||
| fi | ||
| log "setting ${type_arg} hostname to ${host_name}" | ||
| /bin/hostnamectl "--${type_arg}" set-hostname "${host_name}" | ||
| exit 0 | ||
| } | ||
| cli_run() { | ||
| mode="${1:?mode must be the first argument}"; shift; | ||
| case "${mode}" in | ||
| wait_localhost) wait_localhost;; | ||
| set_valid_hostname) hname="${1:?hostname is a required last argument}"; | ||
| set_valid_hostname "${hname}";; | ||
| *) log "unknown mode ${mode}"; exit 1;; | ||
| esac | ||
| } | ||
| # Allow the functions to be sourced. This can be run either as a | ||
| # standalone command or in systemd or part of NetworkManager. | ||
| if [[ "${BASH_SOURCE[0]}" == "${0}" ]]; then | ||
| cli_run ${@} | ||
| fi | ||
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