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+---
+title: "Running alpine in memory with data mode"
+date: 2023-04-30
+tags: ['alpine', 'linux']
+---
+
+# Local testing
+
+To facilitate iteration and testing of this setup, we can use `qemu` and for the
+whole setup  we will be using two disks: one for mounting the /var folder and
+another for storing lbu files (more on that later). To create the two images,
+follow these steps:
+
+```bash 
+qemu-img create -f qcow2 var.cow2 10G
+qemu-img create -f qcow2 media.cow2 5G
+```
+
+Those images have arbitrary sizes and probably won't even required that much for
+this setup so feel free to choose another size. 
+
+Once you have created the images go to alpine download page[^1] and grab the
+latest virtual image.
+
+We all of that we can now start the virtual machine 
+
+```bash
+qemu-system-x86_64 \
+    -machine accel=kvm \
+    -display gtk \
+    -m 2048 \
+    -boot d \
+    -cdrom alpine-virt-3.17.3-x86_64.iso \
+    -drive file=var.cow2,if=virtio \
+    -drive file=media.cow2,if=virtio
+```
+
+For more info about what are those parameters head to `qemu` documentation[^2].
+Just pay attention to the `-boot d` option which will force cdrom to boot first
+(more on that later as well).
+
+# Setting up environment
+
+Before we can run `setup-alpine` we need to mount a persistent media folder so
+it can be picked up by the script and used to store the `lbu` files. To do so we
+need to install some extra package that are not available in the live ISO.
+
+Run `setup-interfaces` to configure interfaces. The default values will do.
+After that start the networking service `rc-service networking start`. Now we
+have internet we can setup a repository. You could edit `/etc/apk/repositories`
+directly but there is handy command for that already `setup-apkrepos`. Run it
+and pick any option you see fit. I'd go for `f` but `1` also works.
+
+Now we can install some packages required for the remaining of the setup:
+
+```bash
+apk add lsbkl e2fsprogs
+```
+
+`lsblk` is useful to identify devices and `e2fsprogs` will provide `ext4`
+support.
+
+Run `lsblk` and will display the device we attached, e.g.:
+
+```bash
+vda     253:0   0   10G     0   disk
+vdb     253:0   0    5G     0   disk
+```
+
+Now let's format and mount `vdb` on `/media`.
+
+```bash
+# formatting using ext4
+mkfs.ext4 /dev/vdb
+
+# creating target folder for mouting
+# the name is arbitrary, feel free to choose another one
+mkdir /media/vdb
+
+# mouting 
+mount -t ext4 /dev/vdb /media/vdb
+```
+
+To confirm if device is mounted you can run `df -h /media/vdb`, it shows the
+size and which device is mounted on that folder.
+
+# Setting up alpine on data mode
+
+Now we can run `setup-alpine`. Choose whatever options fits your need up to the
+point where it asks to choose the device. It may repeat some of the step we
+already did but it is be fine.
+
+When it asks to choose a disks to use enter the name of disk, which, in this
+particularly setup, is `vda`. Then it will ask to choose how you would like to
+run alpine[^3], pick `data`. 
+
+Now it will prompt to choose which media device we want to use for storing the
+`lbu` files. By default it should the media folder we mounted in the previous
+step, if not just enter `vdb`. Select place for cache. Default is fine.
+
+The cache folder is used to store the apk files we come to add. Since it does
+not have internet access when booting it needs to store those extra package in
+folder so later it can be restored.
+
+**Warning**, do not reboot now. We need to use `lbu` to make a backup of all
+changes we did, otherwise everything will be lost. Take a careful read of the
+`lbu` documentation[^4], it will provide the necessary information to understand
+how `lbu` works.
+
+Run `lbu commit` to backup it. You can check the `apkvol` file stored in the
+`/media/vdb/`. Now you changes as saved and you are good to reboot.
+
+The live ISO will look for `apkvol` files and try to restore it. That is why it
+is required the ISO to be the first to boot. There is no boot info store
+anywhere else since the one device is used to store `lbu` and the other one is
+mount on `/var` so we use live ISO to boot and restore the state.
+
+You can check here[^5] how that is possible and here [^6] how we can expand that
+idea and netboot using the apkvol to boot any machine to specific state.
+
+# Making changes
+
+After rebooting your system, you can now log into your fresh installation. You
+can then install a new package, such as vim, using the command `apk add vim`.
+However, if you reboot the system again, the vim package will be lost and you
+will need to reinstall it.
+
+If you run `lbu status` will show what was changed and in this case
+`/etc/apk/world`. The world file store all the package you have installed and
+since you have added a new packaged it has been modified. `lbu
+commit` to persist it.
+
+You can check the `/media/vdb/cache` folder to see that it has stored the vim
+package and its dependencies.
+
+# Why /var?
+
+The /var folder is a directory in Linux that is used to store variable data
+files as the contents of this folder can change by the OS. This folder contains
+files that are not critical to the basic operation of the system, but are
+instead used for tasks such as logging, spooling, and caching. For example
+postgresql store all its data on the var folder allowing us to use a database on
+data mode and still have its data persistent between boots.
+
+# In conclusion
+
+We can take advantage of speed boost provided by `tmpfs`, and we can still
+restore the system state even if the computer is rebooted. The only thing to
+keep in mind is to commit any changes made before rebooting  ;).
+
+[^1]: https://alpinelinux.org/downloads/
+[^2]: https://www.qemu.org/docs/master/system/invocation.html
+[^3]: https://wiki.alpinelinux.org/wiki/Installation
+[^4]: https://wiki.alpinelinux.org/wiki/Alpine_local_backup
+[^5]: https://bitfehler.srht.site/posts/2022-11-28_messing-with-your-initramfs---alpine-edition.html
+[^6]: https://www.apalrd.net/posts/2022/alpine_pxe/