111 lines
3.8 KiB
Markdown
111 lines
3.8 KiB
Markdown
#Generate initramfs for ubuntu that can fetch rootfs from http server
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## Steps
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* Boot in to live Ubuntu disk
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* Open Terminal
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* Run `sudo -i`
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* Put insert content of below to files `/usr/share/initramfs-tools/modules.d/pxe` and `/usr/share/initramfs-tools/scripts/pxe`
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* Run `mkinitramfs -o /root/initrd.img`
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* Migrate `/root/initrd.img` to PXE server
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* Add new boot parameters to pxelinux config on pxe server
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### New Required boot parameters
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```
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rooturl=http://<serverIP>/path/to/file boot=pxe maxTryCount=10 initdwnsize=2G
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```
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### /usr/share/initramfs-tools/modules.d/pxe
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```
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overlayfs
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squashfs
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```
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### /usr/share/initramfs-tools/scripts/pxe
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Script from https://habr.com/en/post/513568/
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```
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#!/bin/bash
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mountroot()
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{
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maxTryCount=5
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squashfsFile="/dwn/rootfs.squashfs"
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squashfsMountPoint="/mnt/ro"
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tmpfsMountPoint="/mnt/rw"
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overlayfsUppderDir="$tmpfsMountPoint/upper"
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overlayfsWorkDir="$tmpfsMountPoint/work"
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overlayfsDir="/mnt/overlayfs"
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tryCount="1"
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# run udevadm
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wait_for_udev 10
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# parce kernel cmdline args. rooturl needed
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for x in $(cat /proc/cmdline); do
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case $x in
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rooturl=*)
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export rooturl=${x#rooturl=}
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;;
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maxTryCount=*)
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export maxTryCount=${x#maxTryCount=}
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;;
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initdwnsize=*)
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export initdwnsize=${x#initdwnsize=}
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;;
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esac
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done
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log_begin_msg "Loading modules"
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modprobe squashfs || panic "can't modprobe squashfs"
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modprobe af_packet || panic "can't modprobe af_packet"
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modprobe overlay || panic "can't modprobe overlayfs"
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log_success_msg "modules loaded"
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log_begin_msg "Generating RamDisk for download.."
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mkdir /dwn
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mount -t tmpfs -o rw,size=${initdwnsize} tmpfs /dwn
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log_success_msg "Generating RamDisk for download [ OK ]"
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log_begin_msg "Configure network"
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configure_networking || panic "Can't configure network"
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log_success_msg "Network configured"
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log_begin_msg "Download rootfs"
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while [ ! -f ${squashfsFile} ] && [ ${tryCount} -le ${maxTryCount} ]; do
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wget ${rooturl} -O ${squashfsFile} || log_failure_msg "Can't download rootfs, count ${tryCount}"
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tryCount=$(( ${tryCount} + 1 ))
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sleep 0.5
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done
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if [ -f ${squashfsFile} ]
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then
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log_success_msg "Rootfs downloaded"
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else
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panic "Can't download rootfs"
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fi
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log_begin_msg "Mount rootfs"
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mkdir -p $squashfsMountPoint
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mount -t squashfs -o loop $squashfsFile $squashfsMountPoint || panic "Can't mount rootfs"
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log_success_msg "Rootfs mounted"
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log_begin_msg "Mount tmpfs"
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mkdir -p $tmpfsMountPoint
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mount -t tmpfs none $tmpfsMountPoint || panic "Tmpfs mount failed "
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log_success_msg "Tmpfs mounted"
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log_begin_msg "Mount overlayfs"
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mkdir -p $overlayfsUppderDir $overlayfsWorkDir $overlayfsDir
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mount -t overlay overlay -o lowerdir=$squashfsMountPoint,upperdir=$overlayfsUppderDir,workdir=$overlayfsWorkDir $overlayfsDir \
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|| panic "Overlayfs mount failed"
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log_success_msg "Overlayfs mounted"
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log_begin_msg "Move tmpfs and squashfs to new root"
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mkdir -p $overlayfsDir/$tmpfsMountPoint $overlayfsDir/$squashfsMountPoint
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mount --move $squashfsMountPoint $overlayfsDir/$squashfsMountPoint || panic "squashfs move failed"
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mount --move $tmpfsMountPoint $overlayfsDir/$tmpfsMountPoint || panic "tmpfs move failed"
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log_success_msg "Tmpfs and squashfs moved"
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log_begin_msg "Move overlayfs to new root"
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mount --move $overlayfsDir ${rootmnt} || panic ""
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}
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``` |