Re: [PATCH] Add /etc/resolve.conf to kdump initrd if it's managed manually

[Dave Young]

Hi Coiby,

On Fri, 10 Nov 2023 at 08:40, Coiby Xu <coxu(a)redhat.com&gt; wrote:
>  Some users may choose to manage /etc/resolve.conf manually. In this case,
>  network dumping will not work because DNS resolution doesn't work. Copy
>  /etc/resolve.conf to kdump initrd if this file is not managed by
>  systemd-resolved or NetworkManager.
>
>  Fixes: 63c3805c ("Set up kdump network by directly copying NM connection profile to
> initrd")
>  Reported-by: Curtis Taylor <cutaylor(a)redhat.com&gt;
>  Cc: Jie Li <jieli(a)redhat.com&gt;
>  Signed-off-by: Coiby Xu <coxu(a)redhat.com&gt;
>  ---
>   dracut-module-setup.sh | 14 ++++++++++++++
>   1 file changed, 14 insertions(+)
>
>  diff --git a/dracut-module-setup.sh b/dracut-module-setup.sh
>  index ff53d084..e6355973 100755
>  --- a/dracut-module-setup.sh
>  +++ b/dracut-module-setup.sh
>  @@ -563,6 +563,19 @@ kdump_collect_netif_usage() {
>       fi
>   }
>
>  +kdump_install_resolv_conf() {
>  +
>  +    local _resolv_conf=/etc/resolv.conf
>  +
>  +    # Some users may choose to manage /etc/resolve.conf manually.
>  +    #
>  +    # We can tell this case by confirming this file is not manged by
>  +    # systemd-resolved or NetworkManager.
>  +    if ! grep -qs "^nameserver 127.0.0.53" "$_resolv_conf"
> && ! grep -qs "^# Generated by NetworkManager"
> "$_resolv_conf"; then 
Is the 127.0.0.53, is it systemd-resolved specific?  How about just
check the status of systemd-resolvd by checking return value of below:
systemctl -q is-active systemd-resolved

Otherwise for NetworkManager setup, it could be that people just edit
the NM generated resolv.conf, but keep the comment line there:
https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/8/...

If we just blindly install the resolv.conf, I think it will be
overwritten by NM in kdump kernel initramfs during bootup if people
use NM, so it does not matter to have it copied without any checking.


>  +        dracut_install "$_resolv_conf"
>  +    fi
>  +}
>  +
>   # Setup dracut to bring up network interface that enable
>   # initramfs accessing giving destination
>   kdump_install_net() {
>  @@ -575,6 +588,7 @@ kdump_install_net() {
>           kdump_setup_znet
>           kdump_install_nm_netif_allowlist "$_netifs"
>           kdump_install_nic_driver "$_netifs"
>  +        kdump_install_resolv_conf
>       fi
>   }
>
>  --
>  2.41.0
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Thanks
Dave