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Diffstat (limited to 'content/posts/2023-04-30-using-data-mode-alpine.md')
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diff --git a/content/posts/2023-04-30-using-data-mode-alpine.md b/content/posts/2023-04-30-using-data-mode-alpine.md index d0e7623..f8465ed 100644 --- a/content/posts/2023-04-30-using-data-mode-alpine.md +++ b/content/posts/2023-04-30-using-data-mode-alpine.md @@ -6,23 +6,23 @@ 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: +To make testing easier, we can use `qemu`, which will allow us to test the +configuration before going for the real machine. For this 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 with `qemu` run: ```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. +Those images have arbitrary sizes and probably we won't even required that much +for this setup so feel free to choose pick whatever size you want. -Once you have created the images go to alpine download page[^1] and grab the +Once we 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 +We all of that we can now start the virtual machine, run: ```bash qemu-system-x86_64 \ @@ -36,20 +36,21 @@ qemu-system-x86_64 \ ``` 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). +Just make sure to add `-boot d` option which will force cdrom to boot first +(more on that later). # 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. +it can be used by `lbu` to store backup 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. +First we need to connect to internet. Run `setup-interfaces` to configure +interfaces, default values will do. After that start the networking service +`rc-service networking start`. Now we should have internet. After that we need +to setup a repository. You could edit `/etc/apk/repositories` directly but +there is handy command that does 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: @@ -81,49 +82,50 @@ mkdir /media/vdb 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. +To confirm if device is mounted you can run `df -h /media/vdb`, and it should +show 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. +Now we can run `setup-alpine`. Choose whatever options fits your need until up +to the point where it asks to choose a device. -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`. +When it asks to choose a disks to use enter the name of the data 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 +Now it will prompt to choose which media device we want to use for storing `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. +step, if not just enter `vdb`. Then 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. +The cache folder is also 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. +changes we did, otherwise everything will be lost on reboot. Take a careful +read on 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. +`/media/vdb/`. Now that we have saved our changes, we 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. +The `initramfs` of the live ISO will look for `apkvol` files and try to restore +it and that is why cdroom is required to be the first thing to boot. + +We can also notice that there is no boot info stored anywhere else. One device is +used to store the `lbu` files and the other one is used ,later after boot, to +mount `/var`, so the live iso is required. 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 +After rebooting your system, you can 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. +will need to reinstall it again after boot. 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 @@ -135,12 +137,11 @@ 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. +The `/var` 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, and by mouting the +var folder into a persistent file system it allows us to use a database os +running on a tmpfs and still have its data persistent between boots. # In conclusion |