Re: [cip-dev][isar-cip-core]RFC v2 6/9] Create systemd mount units for a etc overlay

From: Christian Storm <christian.storm@siemens.com>
To: cip-dev@lists.cip-project.org
Subject: Re: [cip-dev][isar-cip-core]RFC v2 6/9] Create systemd mount units for a etc overlay
Date: Wed, 17 Nov 2021 13:11:31 +0100	[thread overview]
Message-ID: <20211117121131.as2eyks3q76x75sq@MD1ZFJVC.ad001.siemens.net> (raw)
In-Reply-To: <20211116112752.1521211-7-Quirin.Gylstorff@siemens.com>

> From: Quirin Gylstorff <quirin.gylstorff@siemens.com>
> 
> As /etc is read-only and needs to be accessed by the initrd
> move the user defined settings to a overlay in /var/local/etc.
> 
> Signed-off-by: Quirin Gylstorff <quirin.gylstorff@siemens.com>
> ---
>  .../etc-overlay-fs/etc-overlay-fs_0.1.bb         | 16 ++++++++++++++++
>  .../etc-overlay-fs/files/etc-hostname.service    | 14 ++++++++++++++
>  .../etc-overlay-fs/files/etc-sysusers.service    | 14 ++++++++++++++
>  recipes-core/etc-overlay-fs/files/etc.mount      | 13 +++++++++++++
>  .../files/overlay-parse-etc.service              | 12 ++++++++++++
>  recipes-core/etc-overlay-fs/files/postinst       |  6 ++++++
>  recipes-core/images/cip-core-image-read-only.bb  |  1 +
>  7 files changed, 76 insertions(+)
>  create mode 100644 recipes-core/etc-overlay-fs/etc-overlay-fs_0.1.bb
>  create mode 100644 recipes-core/etc-overlay-fs/files/etc-hostname.service
>  create mode 100644 recipes-core/etc-overlay-fs/files/etc-sysusers.service
>  create mode 100644 recipes-core/etc-overlay-fs/files/etc.mount
>  create mode 100644 recipes-core/etc-overlay-fs/files/overlay-parse-etc.service
>  create mode 100755 recipes-core/etc-overlay-fs/files/postinst
> 
> diff --git a/recipes-core/etc-overlay-fs/etc-overlay-fs_0.1.bb b/recipes-core/etc-overlay-fs/etc-overlay-fs_0.1.bb
> new file mode 100644
> index 0000000..f1c8349
> --- /dev/null
> +++ b/recipes-core/etc-overlay-fs/etc-overlay-fs_0.1.bb
> @@ -0,0 +1,16 @@
> +inherit dpkg-raw
> +
> +SRC_URI = "file://postinst \
> +           file://etc.mount \
> +           file://overlay-parse-etc.service \
> +           file://etc-hostname.service \
> +           file://etc-sysusers.service"
> +
> +do_install[cleandirs]+="${D}/lib/systemd/system ${D}/var/local/etc ${D}/var/local/.atomic"
> +do_install() {
> +    TARGET=${D}/lib/systemd/system
> +    install -m 0644 ${WORKDIR}/etc.mount ${TARGET}/etc.mount
> +    install -m 0644 ${WORKDIR}/overlay-parse-etc.service  ${TARGET}/overlay-parse-etc.service
> +    install -m 0644 ${WORKDIR}/etc-hostname.service ${TARGET}/etc-hostname.service
> +    install -m 0644 ${WORKDIR}/etc-sysusers.service ${TARGET}/etc-sysusers.service
> +}
> diff --git a/recipes-core/etc-overlay-fs/files/etc-hostname.service b/recipes-core/etc-overlay-fs/files/etc-hostname.service
> new file mode 100644
> index 0000000..2306b9f
> --- /dev/null
> +++ b/recipes-core/etc-overlay-fs/files/etc-hostname.service
> @@ -0,0 +1,14 @@
> +[Unit]
> +Description=set hostname /etc overlay-aware
> +Before=network-pre.target
> +Wants=network-pre.target
> +Requires=etc.mount
> +After=etc.mount
> +
> +[Service]
> +Type=oneshot
> +RemainAfterExit=yes
> +ExecStart=/bin/hostname --boot --file /etc/hostname
> +
> +[Install]
> +WantedBy=basic.target
> diff --git a/recipes-core/etc-overlay-fs/files/etc-sysusers.service b/recipes-core/etc-overlay-fs/files/etc-sysusers.service
> new file mode 100644
> index 0000000..6caf6b0
> --- /dev/null
> +++ b/recipes-core/etc-overlay-fs/files/etc-sysusers.service
> @@ -0,0 +1,14 @@
> +[Unit]
> +Description=make systemd-sysusers /etc overlay aware
> +Before=network-pre.target
> +Wants=network-pre.target
> +Requires=etc.mount
> +After=etc.mount
> +
> +[Service]
> +Type=oneshot
> +RemainAfterExit=yes
> +ExecStart=/usr/bin/systemd-sysusers
> +
> +[Install]
> +WantedBy=basic.target

Hm, why do you replace/create those services instead of augmenting the
current default ones via conf.d'lets?
Why is this one here dependent on network?
Why does this differ that much from upstream service files, see, e.g.,
https://github.com/systemd/systemd/blob/main/units/systemd-sysusers.service

> diff --git a/recipes-core/etc-overlay-fs/files/etc.mount b/recipes-core/etc-overlay-fs/files/etc.mount
> new file mode 100644
> index 0000000..f0ae3c5
> --- /dev/null
> +++ b/recipes-core/etc-overlay-fs/files/etc.mount
> @@ -0,0 +1,13 @@
> +[Unit]
> +Description=Overlay-mount /etc
> +Requires=var.mount
> +After=var.mount
> +
> +[Mount]
> +What=overlay
> +Where=/etc
> +Type=overlay
> +Options=noauto,x-systemd.automount,lowerdir=/etc,upperdir=/var/local/etc,workdir=/var/local/.atomic
> +
> +[Install]
> +WantedBy=local-fs.target
> diff --git a/recipes-core/etc-overlay-fs/files/overlay-parse-etc.service b/recipes-core/etc-overlay-fs/files/overlay-parse-etc.service
> new file mode 100644
> index 0000000..062bb40
> --- /dev/null
> +++ b/recipes-core/etc-overlay-fs/files/overlay-parse-etc.service
> @@ -0,0 +1,12 @@
> +[Unit]
> +Description=Reload Configuration from the etc overlay
> +Requires=etc.mount
> +After=etc.mount
> +
> +[Service]
> +Type=oneshot
> +RemainAfterExit=yes
> +ExecStartPre=!/bin/systemctl daemon-reload
> +ExecStart=!/bin/systemctl --no-block isolate multi-user.target

Wow, this is a big cannon, why do you need this? Isn't there another way?

> +[Install]
> +WantedBy=local-fs.target
> diff --git a/recipes-core/etc-overlay-fs/files/postinst b/recipes-core/etc-overlay-fs/files/postinst
> new file mode 100755
> index 0000000..35641af
> --- /dev/null
> +++ b/recipes-core/etc-overlay-fs/files/postinst
> @@ -0,0 +1,6 @@
> +#!/bin/sh
> +
> +deb-systemd-helper enable etc.mount  || true
> +deb-systemd-helper enable overlay-parse-etc.service || true
> +deb-systemd-helper enable etc-hostname.service || true
> +deb-systemd-helper enable etc-sysusers.service || true
> diff --git a/recipes-core/images/cip-core-image-read-only.bb b/recipes-core/images/cip-core-image-read-only.bb
> index 7ef2dc2..ceb6ac4 100644
> --- a/recipes-core/images/cip-core-image-read-only.bb
> +++ b/recipes-core/images/cip-core-image-read-only.bb
> @@ -2,6 +2,7 @@ require cip-core-image.bb
>  
>  SQUASHFS_EXCLUDE_DIRS += "home var"
>  
> +IMAGE_INSTALL += "etc-overlay-fs"
>  IMAGE_INSTALL += "tmp-fs"
>  IMAGE_INSTALL_remove += "initramfs-abrootfs-secureboot"
>  
> -- 
> 2.30.2
> 

Kind regards,
   Christian

-- 
Dr. Christian Storm
Siemens AG, Technology, T RDA IOT SES-DE
Otto-Hahn-Ring 6, 81739 München, Germany