From 3bdfbb1bbe6d2ef588fe7a6f67ecf314a6ab3e30 Mon Sep 17 00:00:00 2001
From: Vitaliy Filippov <vitalif@yourcmc.ru>
Date: Fri, 14 Aug 2020 16:25:49 +0300
Subject: [PATCH] Fix notes

---
 README.md                             | 24 +++++++++++++-----------
 local-block_dm-era.sh => zz_dm-era.sh |  6 ++++--
 2 files changed, 17 insertions(+), 13 deletions(-)
 rename local-block_dm-era.sh => zz_dm-era.sh (52%)

diff --git a/README.md b/README.md
index e7be367..6e177ec 100644
--- a/README.md
+++ b/README.md
@@ -22,20 +22,22 @@ and seems to handle fsyncs correctly.
    on disk at a time, but anyway, a 512 MB or 1 GB partition will be more than enough.
    For example you can shrink the main partition a bit and add the dm-era partition after it.
 2. Zero out the new metadata partition: `dd if=/dev/zero of=<META_PARTITION> bs=1048576`
-3. Copy `local-block_dm-era.sh` to `/etc/initramfs-tools/scripts/local-block`
+3. Copy `zz_dm-era.sh` to `/etc/initramfs-tools/scripts/local-block`
    and adjust `DATA_DEVICE`, `META_DEVICE` and `ERA_DEVICE_NAME` in it.
-   Use GPT and partition UUIDs to be safe because dm-era doesn't check
-   if you supply the correct partition to it.
-4. Edit `/etc/fstab` and change your actual device to `/dev/mapper/<ERA_DEVICE_NAME>`,
+   Use partition IDs (`/dev/disk/by-partuuid/*` for GPT partitions, `/dev/disk/by-id/md-uuid-*` for mdadm, etc)
+   to be safe because dm-era doesn't check if you supply correct partitions to it.
+4. Add `dm_era` to `/etc/initramfs-tools/modules`.
+5. Edit `/etc/fstab` and change your actual device to `/dev/mapper/<ERA_DEVICE_NAME>`,
    for example `/dev/mapper/root_era`.
-5. Repeat it for more partitions if you want.
-6. If you do it for the root partition also change `/etc/default/grub`:
+6. Repeat it for more partitions if you want.
+7. Run `update-initramfs -u -k all`.
+8. If you do it for the root partition also change `/etc/default/grub`:
    `GRUB_CMDLINE_LINUX="root=/dev/mapper/root_era"` and refresh grub config with `update-grub`.
-7. Reboot.
-8. Install dm-era tools (`era_invalidate`) with `apt-get install thin-provisioning-tools` on your target host.
-9. Install `era_copy` and `era_apply` (`make install` from this repository) on both hosts (target host and backup host).
-10. Do an initial full partition backup with block-level copy.
-11. Now you can use `backup.sh` to perform incremental backups of the dm-era device
+9. Reboot.
+10. Install dm-era tools (`era_invalidate`) with `apt-get install thin-provisioning-tools` on your target host.
+11. Install `era_copy` and `era_apply` (`make install` from this repository) on both hosts (target host and backup host).
+12. Do an initial full partition backup with block-level copy.
+13. Now you can use `backup.sh` to perform incremental backups of the dm-era device
     over ssh from the backup host. Just change variables at the top of the script so it matches
     your device configuration.
 
diff --git a/local-block_dm-era.sh b/zz_dm-era.sh
similarity index 52%
rename from local-block_dm-era.sh
rename to zz_dm-era.sh
index a468a6f..1dd79f3 100755
--- a/local-block_dm-era.sh
+++ b/zz_dm-era.sh
@@ -1,4 +1,5 @@
 #!/bin/sh
+# Put into /etc/initramfs-tools/scripts/local-block
 
 set -e
 
@@ -18,7 +19,8 @@ esac
 
 modprobe dm-era
 
-DATA_DEVICE=/dev/disk/by-partuuid/ca313f78-7911-994b-b465-5cda9a3ceafb
-META_DEVICE=/dev/disk/by-partuuid/be47b5e2-1587-1243-9c5f-f9e165df5c30
+DATA_DEVICE=`realpath /dev/disk/by-partuuid/ca313f78-7911-994b-b465-5cda9a3ceafb`
+META_DEVICE=`realpath /dev/disk/by-partuuid/be47b5e2-1587-1243-9c5f-f9e165df5c30`
 ERA_DEVICE_NAME=root_era
+[ -z "$DATA_DEVICE" -o -z "$META_DEVICE" ] && exit 0
 dmsetup create $ERA_DEVICE_NAME --table "0 `/sbin/blockdev --getsz $DATA_DEVICE` era $META_DEVICE $DATA_DEVICE 1024"