# Installing &debian-gnu; from a Unix/Linux System

This section explains how to install &debian-gnu; from an existing Unix or Linux system, without using the menu-driven installer as explained in the rest of the manual. This cross-install HOWTO has been requested by users switching to &debian-gnu; from Red Hat, Mandriva, and SUSE. In this section some familiarity with entering *nix commands and navigating the file system is assumed. In this section, `$` symbolizes a command to be entered in the user's current system, while `#` refers to a command entered in the &debian; chroot.

Once you've got the new &debian; system configured to your preference, you can migrate your existing user data (if any) to it, and keep on rolling. This is therefore a zero downtime &debian-gnu; install. It's also a clever way for dealing with hardware that otherwise doesn't play friendly with various boot or installation media.

As this is a mostly manual procedure, you should bear in mind that you will need to do a lot of basic configuration of the system yourself, which will also require more knowledge of &debian; and of &arch-kernel; in general than performing a regular installation. You cannot expect this procedure to result in a system that is identical to a system from a regular installation. You should also keep in mind that this procedure only gives the basic steps to set up a system. Additional installation and/or configuration steps may be needed.

## Getting Started

With your current *nix partitioning tools, repartition the hard drive as needed, creating at least one filesystem plus swap. You need around &base-system-size;MB of space available for a console only install, or about &task-desktop-lxde-inst;MB if you plan to install X (more if you intend to install desktop environments like GNOME or KDE Plasma).

Next, create file systems on the partitions. For example, to create an ext3 file system on partition `/dev/sda6` (that's our example root partition):

    # mke2fs -j /dev/sda6

To create an ext2 file system instead, omit `-j`.

Initialize and activate swap (substitute the partition number for your intended &debian; swap partition):

    # mkswap /dev/sda5
    # sync
    # swapon /dev/sda5

Mount one partition as `/mnt/debinst` (the installation point, to be the root (`/`) filesystem on your new system). The mount point name is strictly arbitrary, it is referenced later below.

    # mkdir /mnt/debinst
    # mount /dev/sda6 /mnt/debinst

If you want to have parts of the filesystem (e.g. /usr) mounted on separate partitions, you will need to create and mount these directories manually before proceeding with the next stage.

## Install `debootstrap`

The utility used by the &debian; installer, and recognized as the official way to install a &debian; base system, is `debootstrap`. It uses `wget` and `ar`, but otherwise depends only on `/bin/sh` and basic Unix/Linux tools

These include the GNU core utilities and commands like `sed`, `grep`, `tar` and `gzip`.

. Install `wget` and `ar` if they aren't already on your current system, then download and install `debootstrap`.

Or, you can use the following procedure to install it manually. Make a work folder for extracting the .deb into:

    # mkdir work
    # cd work

The `debootstrap` binary is located in the &debian; archive (be sure to select the proper file for your architecture). Download the `debootstrap` .deb from the pool, copy the package to the work folder, and extract the files from it. You will need to have root privileges to install the files.

    # ar -x debootstrap_0.X.X_all.deb
    # cd /
    # zcat /full-path-to-work/work/data.tar.gz | tar xv

## Run `debootstrap`

`debootstrap` can download the needed files directly from the archive when you run it. You can substitute any &debian; archive mirror for `&archive-mirror;/debian` in the command example below, preferably a mirror close to you network-wise. Mirrors are listed at .

If you have a &releasename; &debian-gnu; installation image mounted at `/cdrom`, you could substitute a file URL instead of the http URL: `file:/cdrom/debian/`

Substitute one of the following for `ARCH` in the `debootstrap` command: &supported-archs-in-release;.

    # /usr/sbin/debootstrap --arch ARCH &releasename; \
         /mnt/debinst http://ftp.us.debian.org/debian

If the target architecture is different than the host, you should add the `--foreign` option.

## Configure The Base System

Now you've got a real &debian; system, though rather lean, on disk. `chroot` into it:

    # LANG=C.UTF-8 chroot /mnt/debinst /bin/bash

If the target architecture is different from the host, you will need to first copy qemu-user-static to the new host:

    # cp /usr/bin/qemu-ARCH-static /mnt/debinst/usr/bin
    # LANG=C.UTF-8 chroot /mnt/debinst qemu-ARCH-static /bin/bash

After chrooting you may need to set the terminal definition to be compatible with the &debian; base system, for example:

    # export TERM=xterm-color

Depending on the value of TERM, you may have to install the `ncurses-term` package to get support for it.

If the target architecture is different from the host, you need to finish the multi-stage boot strap:

    /debootstrap/debootstrap --second-stage

### Create device files

At this point `/dev/` only contains very basic device files. For the next steps of the installation additional device files may be needed. There are different ways to go about this and which method you should use depends on the host system you are using for the installation, on whether you intend to use a modular kernel or not, and on whether you intend to use dynamic (e.g. using `udev`) or static device files for the new system.

A few of the available options are:

- install the makedev package, and create a default set of static device files using (after chrooting)

      # apt install makedev
      # mount none /proc -t proc
      # cd /dev
      # MAKEDEV generic

- manually create only specific device files using `MAKEDEV`

- bind mount /dev from your host system on top of /dev in the target system; note that the postinst scripts of some packages may try to create device files, so this option should only be used with care

### Mount Partitions

You need to create `/etc/fstab`.

    # editor /etc/fstab

Here is a sample you can modify to suit:

    # /etc/fstab: static file system information.
    #
    # file system    mount point   type    options                  dump pass
    /dev/XXX         /             ext3    defaults                 0    1
    /dev/XXX         /boot         ext3    ro,nosuid,nodev          0    2

    /dev/XXX         none          swap    sw                       0    0
    proc             /proc         proc    defaults                 0    0

    /dev/cdrom       /media/cdrom  iso9660 noauto,ro,user,exec      0    0

    /dev/XXX         /tmp          ext3    rw,nosuid,nodev          0    2
    /dev/XXX         /var          ext3    rw,nosuid,nodev          0    2
    /dev/XXX         /usr          ext3    rw,nodev                 0    2
    /dev/XXX         /home         ext3    rw,nosuid,nodev          0    2

Use `mount -a` to mount all the file systems you have specified in your `/etc/fstab`, or, to mount file systems individually, use:

    # mount /path   # e.g.: mount /usr

Current &debian; systems have mountpoints for removable media under `/media`, but keep compatibility symlinks in `/`. Create these as as needed, for example:

    # cd /media
    # mkdir cdrom0
    # ln -s cdrom0 cdrom
    # cd /
    # ln -s media/cdrom

You can mount the proc file system multiple times and to arbitrary locations, though `/proc` is customary. If you didn't use `mount -a`, be sure to mount proc before continuing:

    # mount -t proc proc /proc

The command `ls /proc` should now show a non-empty directory. Should this fail, you may be able to mount proc from outside the chroot:

    # mount -t proc proc /mnt/debinst/proc

### Setting Timezone

Setting the third line of the file `/etc/adjtime` to UTC or LOCAL determines whether the system will interpret the hardware clock as being set to UTC respective local time. The following command allows you to set that.

    # editor /etc/adjtime

Here is a sample:

    0.0 0 0.0
    0
    UTC

The following command allows you to choose your timezone.

    # dpkg-reconfigure tzdata

### Configure Networking

To configure networking, edit `/etc/network/interfaces`, `/etc/resolv.conf`, `/etc/hostname` and `/etc/hosts`.

    # editor /etc/network/interfaces

Here are some simple examples from `/usr/share/doc/ifupdown/examples`:

    ######################################################################
    # /etc/network/interfaces -- configuration file for ifup(8), ifdown(8)
    # See the interfaces(5) manpage for information on what options are
    # available.
    ######################################################################

    # The loopback interface isn't really required any longer, but can be used
    # if needed.
    #
    # auto lo
    # iface lo inet loopback

    # To use dhcp:
    #
    # auto eth0
    # iface eth0 inet dhcp

    # An example static IP setup: (network, broadcast and gateway are optional)
    #
    # auto eth0
    # iface eth0 inet static
    #     address 192.168.0.42
    #     network 192.168.0.0
    #     netmask 255.255.255.0
    #     broadcast 192.168.0.255
    #     gateway 192.168.0.1

Enter your nameserver(s) and search directives in `/etc/resolv.conf`:

    # editor /etc/resolv.conf

A simple example `/etc/resolv.conf`:

    search example.com
    nameserver 10.1.1.36
    nameserver 192.168.9.100

Enter your system's host name (2 to 63 characters):

    # echo DebianHostName > /etc/hostname

And a basic `/etc/hosts` with IPv6 support:

    127.0.0.1 localhost
    127.0.1.1 DebianHostName

    # The following lines are desirable for IPv6 capable hosts
    ::1     ip6-localhost ip6-loopback
    fe00::0 ip6-localnet
    ff00::0 ip6-mcastprefix
    ff02::1 ip6-allnodes
    ff02::2 ip6-allrouters
    ff02::3 ip6-allhosts

If you have multiple network cards, you should arrange the names of driver modules in the `/etc/modules` file into the desired order. Then during boot, each card will be associated with the interface name (eth0, eth1, etc.) that you expect.

### Configure Apt

Debootstrap will have created a very basic `/etc/apt/sources.list` that will allow installing additional packages. However, you may want to add some additional sources, for example for source packages and security updates:

    deb-src http://ftp.us.debian.org/debian &releasename; main

    deb http://security.debian.org/ &releasename;-security main
    deb-src http://security.debian.org/ &releasename;-security main

Make sure to run `apt update` after you have made changes to the sources list.

### Configure Locales and Keyboard

To configure your locale settings to use a language other than English, install the `locales` support package and configure it. Currently the use of UTF-8 locales is recommended.

    # apt install locales
    # dpkg-reconfigure locales

To configure your keyboard (if needed):

    # apt install console-setup
    # dpkg-reconfigure keyboard-configuration

Note that the keyboard cannot be set while in the chroot, but will be configured for the next reboot.

## Install a Kernel

If you intend to boot this system, you probably want a &arch-kernel; kernel and a boot loader. Identify available pre-packaged kernels with:

    # apt search &kernelpackage;

Then install the kernel package of your choice using its package name.

    # apt install &kernelpackage;-arch-etc

## Set up the Boot Loader

To make your &debian-gnu; system bootable, set up your boot loader to load the installed kernel with your new root partition. Note that `debootstrap` does not install a boot loader, but you can use `apt` inside your &debian; chroot to do so.

Check `info grub` for instructions on setting up the bootloader. If you are keeping the system you used to install &debian;, just add an entry for the &debian; install to your existing grub2 `grub.cfg`.

Installing and setting up `grub2` is as easy as:

    # apt install grub-pc
    # grub-install /dev/sda
    # update-grub

The second command will install `grub2` (in this case in the MBR of `sda`). The last command will create a sane and working `/boot/grub/grub.cfg`.

Note that this assumes that a `/dev/sda` device file has been created. There are alternative methods to install `grub2`, but those are outside the scope of this appendix.

## Remote access: Installing SSH and setting up access

In case you can login to the system via console, you can skip this section. If the system should be accessible via the network later on, you need to install SSH and set up access.

    # apt install ssh

Root login with password is disabled by default, so setting up access can be done by setting a password and re-enable root login with password:

    # passwd
    # editor /etc/ssh/sshd_config

This is the option to be enabled:

    PermitRootLogin yes

Access can also be set up by adding an ssh key to the root account:

    # mkdir /root/.ssh
    # cat << EOF > /root/.ssh/authorized_keys
    ssh-rsa ....
    EOF

Lastly, access can be set up by adding a non-root user and setting a password:

    # adduser joe
    # passwd joe

## Finishing touches

As mentioned earlier, the installed system will be very basic. If you would like to make the system a bit more mature, there is an easy method to install all packages with standard priority:

    # tasksel install standard

Of course, you can also just use `apt` to install packages individually.

After the installation there will be a lot of downloaded packages in `/var/cache/apt/archives/`. You can free up some diskspace by running:

    # apt clean