Difference between revisions of "Remote installation"

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(It is very different from SSH installation. That page assume the new machine can be hardware accessed.)
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[[Category:Getting and installing Arch]]
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#REDIRECT [[Install from SSH]]
[[zh-CN:Remote Arch Linux Install]]
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This is a guide to replace a running Linux system on a remote server. While Arch makes a good server system, it is not usually the pre-installed distribution of choice.
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{{Warning|Please make sure you understand each step before proceeding. It is easy to destroy your system or to lose critical data, and your service provider will likely charge a lot to help you recover. }}
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==Introduction==
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Many providers offer systems called rescue systems or remote consoles, which is often just a bootdisc stored on a network card. This boots into a rudimentary system which just exists in your RAM. Thus you will have the ability to partition your harddrive as you like.
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This document outlines the solution for servers without a rescue systems but have a swap partition. You can disable the swap partition and set up your intermediate system there. When you finish this tutorial you will have a base Arch Linux, which can be accessed via SSH.
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==Backup and Preparation==
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During the procedure you WILL ERASE ALL DATA on your former server. Backup all your data including mails, webservers, etc. Have all information at your fingertips. Preserve all your server configurations, hostnames, etc.
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Here is a list of data you will likely need:
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* IP address
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* hostname(s), (note: rootserver are mostly also part of the providers domain, check or save your {{ic|/etc/hosts}} before you delete)
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* DNS server (check {{ic|/etc/resolv.conf}})
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* SSH keys (if other people work on your server, they will have to accept new keys otherwise. This includes keys from your Apache, your mail servers, your SSH server and others.)
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* Hardware info (network card, etc. Refer to your pre-installed {{ic|/etc/modules.conf}} )
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* Grub configuration files.
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In general, it is a good idea to have a local copy of your original {{ic|/etc}} directory on your local hard drive.
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==Prepare the intermediate system==
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The intermediate system is the system which is used as a place where you setup your new disc layout and install the final system.  There is no need to install more then the absolutely necessary packages in it. In addition to the base system you will need wget to fetch some software and an ssl server.
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===Create a new swap file===
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If you're paranoid or have very little RAM available you might want to add a swap file as swapspace before you disable the swap partition. Note that you do not need running daemons such as mailserver, http-server etc. When you stop them you can free memory at the remote machine.
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The following commands create a file filed with zeros, formats it as swap space, activates the swap file, forces writing of the buffer cache to the disk, and then checks for active swap files.
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{{bc|1=
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# dd if=/dev/zero of=/swapfile bs=1024 count=512288
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# mkswap /swapfile
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# swapon /swapfile
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# sync
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# cat /proc/swaps
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}}
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===Set old swap partition as new root partition===
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Check {{ic|cfdisk}}, {{ic|/proc/swaps}} or {{ic|/etc/fstab}} to find your swap partition. Assuming your hard drive is located on sdaX (X will be a number).
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Do the following:
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Disable the swap space:
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# swapoff /dev/sdaX
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Create a filesystem on it
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# fdisk /dev/sda
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(set /dev/sdaX ID field to "Linux" - Hex 83)
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# mke2fs -j /dev/sdaX
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Create a directory to mount it in
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# mkdir /mnt/newsys
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Finally mounts the new directory for installing the intermediate system.
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# mount -t ext4 /dev/sdaX /mnt/newsys
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===Install the intermediate system===
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Setup the intermedia system environment for pacman following a method in [[Install from Existing Linux]].
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===Things to check before you boot===
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You will have to chroot into your new system to bring up a kernel. When you're in it you will have to setup a root password, otherwise SSH will not let you into your system. Also your bootloader must be directed to your new system. You might want to configure your bootloader to be able to boot into your old system. This makes it easier to use the recovery console in case you have one.
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mount essential systems
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# mount -o bind /dev /mnt/newsys/dev
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# mount -t proc none /mnt/newsys/proc
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Chroot into your new system:
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# chroot /mnt/newsys /bin/bash
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Make sure you have a network and check by [[Network Configuration#Check the connection|this]] method.
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Now you should have pacman available to manage your system. You will need a kernel and an ssh server to reboot into your rescue system. Once you are installing stuff also consider the editor of your choice (nano, joe) if you dislike vi.
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# pacman -S linux openssh
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Set up a bootloader following guide in [[Installation Guide]]. Set up your bootmanager to the new system
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Before proceeding double check that you:
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# start sshd 
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# set a root password
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All this is necessary to get a working system. Enter {{ic|reboot}}.
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===Prepare a home for your new production server===
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Give the server time to reboot and then ping it to ensure you can access it.
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SSH into your new Arch system. Make sure you understand where you are - at your former swap partition.
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Create filesystems as desired and mount your new root partition to {{ic|/mnt/newsys}}.
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  # mkdir /mnt/newsys
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  # mount -t ext4 /dev/discs/disc0/part3 /mnt/newsys
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==Set up your new system==
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At this point, follow the normal steps of [[Installation Guide]]. Probably the {{ic|genfstab}} script won't work. In that case, you'll need to edit the {{ic|/mnt/etc/fstab}} file by hand. You can use the content of {{ic|/etc/mtab}} as reference.
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Double check that you have performed all necessary steps (as for setting up the rescue system), exit chroot, and reboot.
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===Final Remarks===
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Now you have Arch Linux running at your server. More things need to be done to turn it into something useful.
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Latest revision as of 03:51, 24 November 2015

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