Difference between pages "Initramfs" and "Initramfsmove"

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== What is initramfs? ==
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#REDIRECT [[Initramfs]]
[http://en.wikipedia.org/wiki/Initramfs Wikipedia] defines initramfs as:
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<blockquote>
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initramfs, abbreviated from "initial ram file system", is the successor of initrd. It is a cpio archive of the initial file system that gets loaded into memory during the Linux startup process. The Linux kernel mounts it as root file system and starts the init process from it. This will complete certain tasks before the real root file system is loaded; thus, initramfs needs to contain all of the device drivers and tools needed to mount the real root filesystem.
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</blockquote>
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== Do I need an initramfs? ==
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The reason to build a kernel with an initramfs is mostly for interoperability (e.g. live-cd's) and special features like an included busybox, ssh, etc. But mostly, and that's why we are doing this here now, to have a proper kernel up and running quick'n dirty in a reasonable time without fighting hours and days until a more or less exotic hardware is perfectly run by the kernel. After having a proper basic kernel running with the help of an initramfs, I really recommend you to go a step further and build a true kernel with all features includes without an initramfs. However, relying only on a kernel to boot a system can be quite time consuming, so we have provided several initramfs options for Funtoo. If you have decided to use an initramfs, not just a kernel, check out the options below and choose the one that you like the most.
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== better-initramfs ==
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Piotr's better-initramfs is a popular approach among Funtoo'ers to building an initramfs. It is quick, nice, and shiny. The biggest plus is that, once built, it is kernel version independent.
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=== Installation ===
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To install better-initramfs on your system, change to the <code>/opt</code> directory (or any other directory that you deem suitable) and clone the better-initramfs repository from bitbucket.
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<console>
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###i## cd /opt
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###i## git clone https://bitbucket.org/piotrkarbowski/better-initramfs.git
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</console>
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=== Building <code>/initramfs.cpio.gz</code> ===
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Now that you have better-initramfs on your system, we can make the <code>initramfs.cpio.gz</code> image and move it to <code>/boot</code>.
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{{fancynote| do not run <code>make prepare</code> or <code>make image</code> until you have configured your kernel. If you have not installed / configured a kernel yet, check out: [[Building_a_Kernel_from_Source| Building a Kernel From Source]] and [[Funtoo_Linux_Kernels| Funtoo Linux Kernels]].}}
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<console>
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###i## cd better-initramfs
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###i## bootstrap/bootstrap-all
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###i## make prepare
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###i## make image
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###i## cp output/initramfs.cpio.gz /boot
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</console>
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=== Configuring <code>/etc/boot.conf</code> ===
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Now that the <code>initramfs.cpio.gz</code> file is in <code>/boot</code>, we can configure what we want the initramfs to do for us when the system boots. Below is a table of options that better-initramfs supports (from [https://bitbucket.org/piotrkarbowski/better-initramfs better-initramfs Bitbucket page]):
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==== Options ====
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{| {{table}}
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!Option
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!Description
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|-
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|rescueshell
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|Drop to the rescueshell before mounting rootfs to <code>/newroot</code>
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|-
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|sshd
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|Run the sshd server when the initramfs loads. This allows you to ssh into your initramfs to fix any errors that may have occurred while booting.
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|-
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|sshd_wait=x
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|Wait x number of seconds after starting sshd to continue booting the system.
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|-
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|sshd_port=x
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|Change the port that sshd "listens" on. The default port for sshd is port 22.
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|-
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|binit_net_if=interface
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|Choose which interface the network should be configured on. For example: wlan0, eth0, etc.
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|-
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|binit_net_addr=<ipaddr/cidr>
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|Configure <code>ipaddr</code> with <code>cidr</code> netmask. For example: <code>11.11.11.2/24</code>. If you do not add a netmask, the netmask is assumed to be 32. Furthermore, you will have to configure <code>binit_net_gw</code>.
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|-
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|binit_net_gw=ipaddr
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|The address of your gateway. Only needed if you want to connect to WAN.
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|-
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|rw
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|Mount the rootfs as read-write. By default, the rootfs is mounted as read only.
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|-
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|mdev
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|Use mdev instead of devtmpfs. This option can prove handy on older kernels.
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|-
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|softraid
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|Detect and run RAID arrays.
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|-
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|init=
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|Change the init system. For example, if you are using systemd, change this to <code>/usr/lib/systemd/systemd</code>. The default for this option (<code>/sbin/init</code>) will work fine with OpenRC.
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|-
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|tuxonice
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|Try resuming with TuxOnIce.
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|-
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|uswsusp
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|Try resuming the system with userspace software suspend. This depends on the <code>resume</code> option.
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|-
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|swsusp
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|Try resuming the system with in-kernel suspend. This depends on the <code>resume</code> option.
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|-
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|resume=<device/path>
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|Specify the device and path from which you want to resume.
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|-
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|lvm
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|Scan for volume groups. If any are found, activate them.
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|-
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|luks
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|Run <code>cryptsetup luksOpen</code> on the <code>enc_root</code> variable.
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|-
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|luks_trim
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|Enable support for TRIM on your LUKS encrypted root device. This option is very helpful for those using SSDs.
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|-
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|enc_root=<device>
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|The device that you wish to decrypt using <code>cryptsetup luksOpen</code>.
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|-
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|root=<device>
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|The name of your root device.
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|-
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|rootfstype=<fstype>
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|Specify the type of filesystem that your rootfs uses.
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|-
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|rootdelay=<time (as integer)>
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|How long the initramfs should wait before attempting to mount devices.
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|-
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|rootflags=x
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|Pass x flags to <code>mount</code> as it mounts your rootfs.
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|}
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==== Examples ====
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Below are examples of different use cases for better-initramfs and how your <code>/etc/boot.conf</code> should be configured for them.
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{{fancynote| Realize that your <code>enc_root</code>, <code>root</code>, and <code>rootfstype</code> variables may be different from the examples provided below.}}
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==== Regular ext4 root ====
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{{file|name=/etc/boot.conf|desc= |body=
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"Funtoo Linux" {
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kernel vmlinuz[-v]
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initrd /initramfs.cpio.gz
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params += root=/dev/sdaX rootfstype=ext4
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}
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}}
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==== Encrypted root with lvm ====
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{{file|name=/etc/boot.conf|desc= |body=
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"Funtoo Linux" {
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kernel vmlinuz[-v]
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initrd /initramfs.cpio.gz
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params += enc_root=/dev/sdaX lvm luks luks_trim root=/dev/mapper/funtoo--vg-root rootfstype=ext4
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}
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}}
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==== Encrypted root with lvm and RAID ====
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{{file|name=/etc/boot.conf|desc= |body=
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"Funtoo Linux" {
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kernel vmlinuz[-v]
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initrd /initramfs.cpio.gz
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params += enc_root=/dev/md0 lvm luks luks_trim softraid root=/dev/mapper/funtoo--vg-root rootfstype=ext4
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}
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}}
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== Dracut ==
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=== Installation ===
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To install Dracut, simply emerge it:
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<console>
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###i## emerge dracut
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</console>
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=== Build the initramfs ===
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To build the initrd with dracut, we just execute:
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<console>
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###i## dracut -f --fstab --xz /boot/initramfs-3.2.6-pf.img  3.2.6-pf
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</console>
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Generally, this should be enough!
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If you experience booting problems like missing modules / drivers then just boot from your livecd and fix Dracut or consider changing to another initramfs. You can look into the man page to tweak the command a bit (e.g. --add-drivers "xz dm_crypt" etc...).
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=== Configuring <code>/etc/boot.conf</code> ===
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==== Examples ====
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==== Encrypted root with lvm ====
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{{file|name=/etc/boot.conf|desc= |body=
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boot {
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        generate grub
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        default "Funtoo Linux dracut"
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        timeout 3
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}
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"Funtoo Linux dracut" {
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        kernel vmlinuz[-v]
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        initrd initramfs[-v].img
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        params  = quiet rootfstype=ext4
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        params += luks enc_root=/dev/sda3
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        params += lvm root=/dev/mapper/vg-root
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}
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}}
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[[Category:Kernel]]
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Latest revision as of 17:23, August 5, 2014