overlay.d: add udev rule for stable-root disk

Issue: coreos/fedora-coreos-tracker#759

Signed-off-by: Nikita Dubrovskii <nikita@linux.ibm.com>

overlay.d/05core/usr/lib/dracut/modules.d/35coreos-ignition/coreos-teardown-initramfs.sh

@@ -211,6 +211,8 @@ main() {
     # clean it up so that no information from outside of the
     # real root is passed on to NetworkManager in the real root
     rm -rf /run/NetworkManager/
+
+    rm -rf /dev/disk/by-id/coreos-root-disk
 }
 
 main

overlay.d/05core/usr/lib/dracut/modules.d/35coreos-ignition/count-fs.sh

@@ -0,0 +1,25 @@
+#!/bin/bash
+# Returns amount of filesystems labeled `label`
+
+label=$1
+uids=()
+
+for path in /sys/block/*; do
+    disk=$(basename $path)
+    for pt in /sys/block/$disk/*; do
+        name=$(basename $pt)
+        if [[ "$name" =~ "$disk" ]]; then
+            eval $(udevadm info --query=property -n /dev/$name | grep -e PARTNAME -e ID_FS_UUID_ENC)
+            if [[ "$PARTNAME" == "$label" ]]; then
+                uid=$ID_FS_UUID_ENC
+                if [[ -z $uid ]]; then
+                    uid=$(/usr/lib/udev/scsi-id -ugd /dev/$name || echo $pt)
+                fi
+                uids+=("$uid")
+            fi
+        fi
+    done
+done
+
+uids=($(echo "${uids[@]}" | tr ' ' '\n' | sort -u | tr '\n' ' '))
+echo ${#uids[@]}

overlay.d/05core/usr/lib/dracut/modules.d/35coreos-ignition/module-setup.sh

@@ -22,6 +22,8 @@ install() {
         diff \
         lsblk \
         sed \
+        sort \
+        grep \
         sgdisk
 
     inst_simple "$moddir/coreos-diskful-generator" \
@@ -30,6 +32,11 @@ install() {
     inst_script "$moddir/coreos-gpt-setup.sh" \
         "/usr/sbin/coreos-gpt-setup"
 
+    inst_simple "/usr/lib/udev/rules.d/99-zz-coreos-stable-root.rules"
+
+    inst_script "$moddir/count-fs.sh" \
+        "/usr/bin/count-fs"
+
     inst_script "$moddir/coreos-ignition-setup-user.sh" \
         "/usr/sbin/coreos-ignition-setup-user"
 

overlay.d/05core/usr/lib/udev/rules.d/99-zz-coreos-stable-root.rules

@@ -0,0 +1,19 @@
+# CoreOS-specific symlink for disk holdind filesystem labeled `root`
+
+ACTION!="add|change", GOTO="stable_root_end"
+SUBSYSTEM!="block", GOTO="stable_root_end"
+TEST!="/usr/bin/count-fs", GOTO="stable_root_end"
+
+# First run on disks and check how many filesystems labeled `root` we have
+ENV{DEVTYPE}=="disk" \
+  , PROGRAM=="/usr/bin/count-fs root", RESULT=="1" \
+  , SYMLINK+="disk/by-id/coreos-root-disk"
+
+# During processing of disks there are no UUIDs available, so double check
+# how many filesystems labeled `root` we have, and if it's not unique - remove
+# the symlink
+ENV{DEVTYPE}=="partition", ENV(ID_FS_LABEL_ENC)=="root" \
+  , PROGRAM=="/usr/bin/count-fs root", RESULT!="1" \
+  , RUN{program}+="/bin/rm -f /dev/disk/by-id/coreos-root-disk"
+
+LABEL="stable_root_end"

tests/kola/ignition/stable-root/config.bu

@@ -0,0 +1,10 @@
+variant: fcos
+version: 1.3.0
+storage:
+  disks:
+  - device: /dev/disk/by-id/coreos-root-disk
+    wipe_table: false
+    partitions:
+    - number: 5
+      size_mib: 1024
+      label: toor

tests/kola/ignition/stable-root/test.sh

@@ -0,0 +1,24 @@
+#!/bin/bash
+set -xeuo pipefail
+
+# This test makes sure that ignition is able to use symlink to the disk with `root` fs
+
+# We don't need to test this on every platform. If it passes in
+# one place it will pass everywhere.
+# kola: { "platforms": "qemu-unpriv" }
+
+ok() {
+    echo "ok" "$@"
+}
+
+fatal() {
+    echo "$@" >&2
+    exit 1
+}
+
+link="/dev/disk/by-id/coreos-root-disk"
+if [[ -h "${link}" ]]; then
+    fatal "${link} still exists"
+fi
+
+ok "${link} doesn't exist"