Questions tagged [initramfs]

The "initial RAM file system" is the successor of initrd. It is a root filesystem that is embedded into the kernel and loaded early in the boot process.

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3answers
219k views

How to fix boot into initramfs prompt and “mount: can't read '/etc/fstab': No such file or directory” and “No init found”?

Installing a new system using a GPT partitioned disk dedicated to a single partition, ext4 formatted, extlinux (version 4.05) as bootloader, Ubuntu Core version 13.10 amd64 as rootfs, and Ubuntu linux-...
18
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1answer
12k views

When would you use pivot_root over switch_root?

I'm wanting to understand the Linux init process better in order to netboot a system over ceph rather than nfs. In the process I've come across two forms of switching root. One called switch_root, ...
17
votes
3answers
23k views

Does initramfs use /etc/fstab?

The way I understand it, initramfs is responsible for loading the "real" root filesystem. Now, there are two places where we define that root. First we put an entry in /etc/fstab. Second, we put the ...
15
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6answers
18k views

Why do I need initramfs ?

I found that if I choose jffs or sd as file system(and not initramfs),the kernel size is very small (1.4 MB as compared to with initramfs-3.4MB). It shows that initramfs takes concidreably large space....
15
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1answer
20k views

What is the equivalent of mkinitcpio.conf on debian?

I want to review that the hooks used to build the initrd.img are correct in my debian but I fail to find the /etc/mkinitcpio.conf file like the one in Archlinux, what is the equivalent of this file in ...
15
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4answers
27k views

Mount root filesystem from initramfs

It's a common scenario. For whatever reason, the initramfs (OpenSUSE, in case it matters) has failed to find the root filesystem, so it drops you into a rescue shell. I know perfectly well what device ...
14
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3answers
6k views

Is the entire kernel loaded into memory on boot?

I read through this popular IBM doc (I see it referred quite often on the web) explaining the function of the initial RAM disk. I hit a wall in conceptualizing how this works though. In the doc it ...
11
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3answers
3k views

Why use cpio for initramfs?

I am making my own initramfs following the Gentoo wiki. Instead of the familiar tar and gzip, the page is telling me to use cpio and gzip. Wikipedia says that cpio is used by the 2.6 kernel's ...
11
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3answers
8k views

Why does initramfs mount the root filesystem read-only

What is the reason for the root filesystem being mounted ro in the initramfs (and in initrd). For example the Gentoo initramfs guide mounts the root filesystem with: mount -o ro /dev/sda1 /mnt/root ...
10
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1answer
6k views

How can I force a Ubuntu kernel to fail mounting / and drop into the initramfs rescue shell?

I am trying to customize the initramfs rescue environment and would like to force the kernel to fail mounting / and drop into the (initramfs) rescue shell, as opposed to single user mode. How can I ...
10
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1answer
34k views

How to assemble a specific RAID array without using /etc/mdadm.conf

Is it possible to assemble a specific RAID array using mdadm and its scan-functionality, but without the need for a configuration file? Background: I'm using a custom-made initramfs to setup my ...
10
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2answers
1k views

Difference in execution of init with embedded vs. external initramfs?

I'm building a very minimal Linux system that just consists of the kernel (v4.1-rc5) and an initramfs populated with busybox (v1.23.2). It works fine for the most part, but I observe a difference in ...
9
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2answers
6k views

extract Embedded initramfs

I have a kernel in which one initramfs is embedded. I want to extract it. I got the output x86 boot sector when I do file bzImage I have System.map file for this kernel image. Is there any way to ...
9
votes
7answers
7k views

Hibernation resume fail on linux kernel 4.9.0, Debian 9

I recently upgraded my kernel from 3.16.4 (Debian jessie) to 4.9.0 (Debian stretch). Everything was fine, until I tried to "Hibernate" (suspend to disk). When I use Hibernate option in LXDE, it ...
9
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3answers
4k views

GRUB confuses kernels/initramfs of Ubuntu and Arch Linux installation

I have a machine that used to dual-boot Ubuntu (16.04 currently) and Windows 7, with Ubuntu's GRUB as boot loader. Now I just added Arch Linux as third OS, following the official installation ...
8
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2answers
3k views

How is a Linux kernel capable of accessing its assigned initramfs/initrd?

I'm trying to understand the boot process of a machine as a whole from the time you hit the power button. There's this one piece from bootloader to initramfs stage I don't quite understand among some ...
7
votes
3answers
7k views

How to generate initramfs image with busybox links?

Having been directed to initramfs by an answer to my earlier question (thanks!), I've been working on getting initramfs working. I can now boot the kernel and drop to a shell prompt, where I can ...
7
votes
3answers
6k views

Building a Read-Only Linux System With a Writable Layer in RAM

I have a requirement to boot RHEL 6.6/7.0 into read-only mode with a writable layer only in RAM. I believe this is similar to how live CDs work, in that the file system is read-only, but certain parts ...
7
votes
2answers
638 views

Can initramfs be paged out to swap disk?

I am using initramfs to boot Centos via PXE. The initramfs used memory is listed within the "cached" value in /proc/meminfo or via free. Since I need to calculate performance data, I need to know ...
7
votes
2answers
743 views

Repack the filesystem image from vmlinux.bin (embedded initramfs) without rebuilding?

In How do I extract the filesystem image from vmlinux.bin? and https://wiki.gentoo.org/wiki/Custom_Initramfs#Salvaging methods are presented for getting and unpacking an embedded initramfs/initrd ...
7
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2answers
495 views

How do I know what decompression algorithms are compiled-in into the linux kernel?

If /proc/config.gz is unavailable, how do I know what decompression algorithms the running kernel is capable of using on a compressed cpio initramfs? Is the gzip algorithm always available, even when ...
6
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3answers
2k views

Is making /etc directory read only a bad idea?

I have an embedded system setup built using buildroot and using initramfs. It runs on compact flash device where I have created separate ext3 partitions to mount /etc/ and /var directories as well as ...
6
votes
1answer
4k views

Appending files to initramfs image - reliable?

I'm modifying a bunch of initramfs archives from different Linux distros in which normally only one file is being changed. I would like to automate the process without switching to root user to ...
6
votes
4answers
10k views

Unlock LUKS encrypted Debian root with key file on boot partition

I'm trying to decrypt the Debian root with a key file stored in the boot partition (decrypted partition). This will break the security, but it doesn't matter now. I have to conclude this successfully ...
6
votes
1answer
13k views

Excluding kernel modules through /etc/modprobe.d/blacklist.conf does not work

I don't want to load the kernel module nouveau on my debian box at startup, so I put the following in /etc/modprobe.d/blacklist.conf: blacklist ttm blacklist drm blacklist nouveau I even did a ...
6
votes
2answers
8k views

Initramfs in debootstrap chroot of fully encrypted system

I'm working on a script to create a fully encrypted washable system from debootstrap. It's doing some good, but the initramfs image that comes out does not pick up the cryptroot properly. After ...
6
votes
2answers
1k views

Freeing initramfs ram after switching root when using overlayfs?

I am building a custom Live Linux boot image based on Arch Linux. I've modified the stock initrd to contain a custom script which does the following: After boot, only the initramfs exists. I first ...
6
votes
3answers
3k views

How do I build a read-only Linux system that only writes to the RAM?

This is my current partition structure: Filesystem 1K-blocks Used Available Use% Mounted on tmpfs 127428 0 127428 0% /lib/init/rw udev ...
6
votes
1answer
810 views

Does the kernel delete entries in /dev on an initramfs?

I have a fully custom, minimal, embedded Linux (vanilla, 3.3.8, i486, Vortex86dx) system that boots from an initramfs image. No standard distribution scripts are used, just a single rcS file that does ...
6
votes
1answer
2k views

Adding dropbear to initramfs with dracut on Fedora

I'm trying to add dropbear to my initramfs so I can unlock the encrypted disk through a remote SSH session (as described here). I'm running Fedora 16 which apparently uses dracut to generate the ...
5
votes
1answer
2k views

unable to open luks encrypted device (wrong password)

I'm using CentOS 7 with a luks encrypted root partition. Usually I have to type my password during boot, but sometimes the system doesn't accept it. It reacts as it was wrong, but it isn't. I did not ...
5
votes
1answer
3k views

update-initramfs hangs on debian Stretch

using apt-get upgrade on Debian left me with the decision to update to kernel 4.9.0-6 but the installation never finishes. It always stalls at the following stage: Setting up linux-image-4.9.0-6-...
5
votes
1answer
6k views

Adding a file to /etc of initramfs in Debian Wheezy

I have added the file /etc/initramfs-tools/etc/motd so that it would be available in /etc of the initramfs environment. However, it does not turn up. This is my second try where I gave the file all ...
5
votes
3answers
5k views

Prevent Debian from auto-assembling RAID at boot

I set up a Debian wheezy (7.6), installed openmediavault, and created a software raid 5 with that. It is listed at /dev/md127. Now I want to move that to a virtual XEN VM. To do so, I have to stop ...
5
votes
2answers
150 views

Where to install local software that runs before /usr is available?

I'm writing a local program to be called by a udev IMPORT{program} rule. Normally, I'd install local software in /usr/local, but these udev rules are run when block devices appear. So they're running ...
5
votes
1answer
2k views

update-initramfs failing after upgrading to stretch from jessie

I recently updated one of my Debian boxes to run with stretch, but unfortunately I run in an issue when it comes to the regeneration of the initramfs image. It seems that it doesn't recognize that I ...
5
votes
1answer
5k views

mdadm: no devices listed in conf file were found - Debian 8 with GPT

I have a Debian Jessie (3.16.7-ckt20-1+deb8u3) system with RAID1 on 2x 3TB hard drives. Grub can't be installed into MBR on drives >2TB, thus I have GPT with 1MB bios partition: Device Start ...
5
votes
3answers
4k views

Does /init (or /linuxrc) script creates temporary device nodes in /dev?

Considering that GRUB executes following lines: kernel /vmlinuz root=/dev/sda1 ro initrd /initrd On boot, how does the Linux kernel finds out about /dev/sda1 device node? I know that initrd/...
5
votes
0answers
423 views

How to combine linux kernel and initrd without compiling?

I know that it's possible to extract from a linux kernel the embedded initramfs cpio. I want to know if the reverse operation is possible; i.e., given both a compiled kernel and initramfs archive, how ...
5
votes
0answers
2k views

Mounting squashfs image with read-write overlay for rootfs

I am trying to update a custom initramfs init script to mount a squashfs image as the root file system. I have been testing the mounting of a squash image to a loop device in read only, mounting ...
4
votes
1answer
4k views

How to create ASCII cpio archive (SVR4 with no CRC)?

I have a file in /boot/initramfs.gz extract it using tar -xzvf initramfs.gz -C ./ I got a file initramfs. └──╼ $ file initramfs initramfs: ASCII cpio archive (SVR4 with no CRC) It can be open using ...
4
votes
2answers
1k views

pivot_root from initramfs to new root - error “Invalid argument”

You can not use pivot_root on an initramfs rootfs, you will get Invalid Argument. You can only pivot real filesystems. Indeed: Fedora Linux 28 - this uses the dracut initramfs. Boot into an ...
4
votes
1answer
4k views

md raid not mounted by dracut

Background I'm running Centos 7. Originally, it was running on a single disk that looked something like this: 1 200M EFI System (/boot/efi) 2 500M Microsoft basic (/boot) 3 465.1G ...
4
votes
2answers
4k views

How do I determine if my kernel uses initramfs?

I'm reading up on Wake on Lan on Debian wiki https://wiki.debian.org/WakeOnLan and there is a part that says: If your kernel uses an initramfs image (eg. Debian stock kernels), also run update-...
4
votes
2answers
3k views

/dev/sdb* not available after boot - initramfs does not load uas and usb_storage modules

Initramfs on my Debian testing system is not able automatically load necessary kernel modules for external USB 3 HDD (Seagate Backup Plus 1T) if it was already plugged in when initramfs started. If I ...
4
votes
3answers
48k views

boot problem in linux

I have unfortunately format drive /dev/sda2. So all the /root,/home,swap LVM no longer exists. Because of this my server is unable to work properly. it shows only dracut#>Dracut Error: [ OK ] ...
4
votes
2answers
3k views

How to mark “not fully installed” apt-get package as “successfully installed”

I have installed Debian 7.4 on my Iomega ix2-200 NAS, following this blog. The ix2-200 is running an ARM Marvel CPU and has a 128 MB NAND flash memory. The flash contains an initramfs image (uInitrd) ...
4
votes
1answer
509 views

On Gentoo, ZFS stops working after 0.6.5 update

I just updated my Gentoo system, updating my world, including ZFS. Everything but the kernel. I figured I'd do a reboot first, then build a new kernel. Currently, it's running on kernel 3.17.8-gentoo-...
4
votes
1answer
11k views

After installing a new Kernel in Ubuntu 14.04, rebooting takes me to busybox initramfs. How do I mount a filesystem after that?

I have a virtual machine with Ubuntu 14.04 in it. I recently built and installed linux-3.14.5 kernel on it, and tried to boot into it, but it drops me to BusyBox v1.21.1 built-in shell. Here's what I ...
4
votes
1answer
3k views

How to save a file from an initramfs emergency shell?

I can't boot because of some strange error. There is an error report file generated for me, to supposedly submit it along with a bug report, or whatever. So to help me figure out what the problem is, ...