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问题描述

问题

我的问题是, linuxrc 是做什么的?我的 rootfs 是否需要它?

systemd vs initd 有什么关系?

My question is, What does linuxrc do? Do i need it in my rootfs? Does it have anything to do with using systemd vs initd?

背景

我目前正在尝试为ARM构建 rootfs 7处理器使用Yocto。我对原始BSP项目所做的唯一修改是,我指定要使用 systemd 作为初始化管理器(在 local.conf中完成)。 rootfs 构建( bitbake core-image-minimal )并使用 Mgftool2 我将其加载到板上。当我尝试引导映像时,出现以下错误:

I am currently attempting to build a rootfs for an ARM 7 processor using Yocto. The only modification I have made to the original BSP project is I specified that I would like to use systemd as my initialization manager (done in local.conf). The rootfs builds (bitbake core-image-minimal) and using Mgftool2 I load it onto the board. When I attempt to boot the image i get the following error:

VFS: Mounted root (ext3 filesystem) readonly on device 179:2.
devtmpfs: mounted
Freeing unused kernel memory: 272K (80816000 - 8085a000)
Kernel panic - not syncing: Requested init /linuxrc failed (error -2).
CPU: 0 PID: 1 Comm: swapper/0 Tainted: G        W       4.4.15-v4.4.15+g017b90c #1
Hardware name: Freescale i.MX6 Ultralite (Device Tree)
[<80015d9c>] (unwind_backtrace) from [<80012c14>] (show_stack+0x10/0x14)

这非常有道理,因为在检查了生成的 rootfs 之后,我发现没有名为 linuxrc 的可执行文件。我将u-boot的 default_bootargs 更改为不包含 init = / linurc ,然后再次启动了映像。 (更新#1)

This makes perfect sense because after i examined the rootfs I generated, I found that there was no executable named linuxrc. I changed u-boot's default_bootargs to not include init=/linurc and booted the image again. (Update #1)

更新#1

次要错误是由于systemd需要某些。使用这些参数重建内核后,Linux映像便启动了。我仍然想知道 linuxrc 的确切功能,以及为什么至少它看起来好像我不需要它。

The secondary error was caused by systemd needing certain kernel parameters enabled. Once the kernel was rebuilt with these parameters, the linux image did boot. I am still interested in knowing what exactly linuxrc does and why it at least appears i do not need it.

推荐答案

台式机操作系统上的Linuxrc(/ linuxrc,也通用名称/ init)位于initramfs(ramdisk)上。通常,这是在脚本中执行的,该脚本探查模块,在/ dev中创建临时设备节点,等待并挂载rootfs,然后切换到实际root。如果不使用initramfs,则可以通过符号链接到init。

Linuxrc (/linuxrc, also common name /init) on desktop OSes is on initramfs(ramdisk). Usualy this in script that probed modules, creates temporary device nodes in /dev, waits and mount rootfs, switches to real root. If initramfs is not used it may by symlinked to init.

Systemd使用udev创建/ dev /树,因此不需要它。

Systemd uses udev to create /dev/ tree so it non needed.

桌面linux在initramfs中使用它来安装root。如果直接安装rootfs,则可以从footfs运行。

Desktop linux uses it in initramfs to mount root. If rootfs mounted directly it can run from footfs.

示例/ init从路由器中提取。

Example /init extracted from router.

#!/bin/sh
#

# crucial mountpoints
mount -t proc none /proc
mount -t sysfs none /sys
mount -n tmpfs /var -t tmpfs -o size=17825792
mount -t tmpfs dev /dev

mknod /dev/console c 5 1
mknod /dev/ttyS0 c 4 64
mknod /dev/ttyS1 c 4 65

# setup console, consider using ptmx?
CIN=/dev/console
COUT=/dev/console
exec <$CIN &>$COUT

mknod /dev/null c 1 3
mknod /dev/gpio c 127 0

mknod /dev/zero c 1 5
mknod /dev/tty c 5 0
mknod /dev/tty0 c 4 0
mknod /dev/tty1 c 4 1
mknod /dev/random c 1 8
mknod /dev/urandom c 1 9
mknod /dev/ptmx c 5 2
mknod /dev/mem c 1 1

mknod /dev/watchdog c 10 130

mknod /dev/mtdblock0 b 31 0
mknod /dev/mtdblock1 b 31 1
mknod /dev/mtdblock2 b 31 2
mknod /dev/mtdblock3 b 31 3
mknod /dev/mtdblock4 b 31 4
mknod /dev/mtdblock5 b 31 5
mknod /dev/mtdblock6 b 31 6
mknod /dev/mtdblock7 b 31 7

mknod /dev/mtd0 c 90 0
mknod /dev/mtd1 c 90 2
mknod /dev/mtd2 c 90 4
mknod /dev/mtd3 c 90 6
mknod /dev/mtd4 c 90 8
mknod /dev/mtd5 c 90 10
mknod /dev/mtd6 c 90 12
mknod /dev/mtd7 c 90 14

mknod /dev/ttyUSB0 c 188 0
mknod /dev/ttyUSB1 c 188 1
mknod /dev/ttyUSB2 c 188 2
mknod /dev/ttyUSB3 c 188 3
mknod /dev/ttyUSB4 c 188 4
mknod /dev/ttyUSB5 c 188 5
mknod /dev/ttyUSB6 c 188 6

mknod /dev/ppp  c 108 0

mknod /dev/i2c-0 c 89 0
mknod /dev/i2c-1 c 89 1
mknod /dev/i2c-2 c 89 2
mknod /dev/i2c-3 c 89 3

#
# Create the ubnt-poll-host char dev entries
# The major number is 189
#
# NOTE: wifiN's minor number = N
#
mknod /dev/uph_wifi0 c 189 0

mkdir /dev/pts /dev/shm

# rest of the mounts
mount none /dev/pts -t devpts
if [ -e /proc/bus/usb ]; then
    mount none /proc/bus/usb -t usbfs
fi
echo "...mounts done"

mkdir -p /var/run /var/tmp /var/log /var/etc /var/etc/persistent /var/lock
echo "...filesystem init done"

# insert hal module
[ ! -f /lib/modules/*/ubnthal.ko ] || insmod /lib/modules/*/ubnthal.ko

# making sure that critical files are in place
mkdir -p /etc/rc.d /etc/init.d
# forced update
for f in inittab rc.d/rc.sysinit rc.d/rc rc.d/rc.stop ppp; do
        cp -f -r /usr/etc/$f /etc/$f
done
echo "...base ok"

mkdir -p /etc/udhcpc
# do not update if exist
for f in passwd group login.defs profile hosts host.conf \
fstab udhcpc/udhcpc startup.list; do
    if [ -e /etc/$f ]; then
        echo -n '.'
    else
        cp -f /usr/etc/$f /etc/$f
    fi
done
echo "...update ok"

mkdir -p /etc/sysinit
# make symlinks if do not exist
for f in services protocols shells mime.types ethertypes modules.d; do
    if [ -e /etc/$f ]; then
        echo -n '.'
    else
        ln -s /usr/etc/$f /etc/$f
    fi
done
echo "...symlinks ok"

mkdir -p /etc/httpd
# check if we have uploaded certificates
for f in server.crt server.key; do
    if [ -e /etc/persistent/https/$f ]; then
    ln -s /etc/persistent/https/$f /etc/httpd/$f
    else
    ln -s /usr/etc/$f /etc/httpd/$f
    fi
done
echo "...httpd ok"

CFG_SYSTEM="/tmp/system.cfg"
CFG_RUNNING="/tmp/running.cfg"
CFG_DEFAULT="/etc/default.cfg"

#Starting watchdog manager
/bin/watchdog -t 1 /dev/watchdog

# board data symlinks + default config
if [ -e /sbin/ubntconf ]; then
    /sbin/ubntconf -i $CFG_DEFAULT
    echo "ubntconf returned $?" >> /tmp/ubntconf.log
    echo "...detect ok"
fi

# System configuration
mkdir -p /etc/sysinit/
/sbin/cfgmtd -r -p /etc/ -f $CFG_RUNNING
if [ $? -ne 0 ]; then
    /sbin/cfgmtd -r -p /etc/ -t 2 -f $CFG_RUNNING
    if [ $? -ne 0 ]; then
        cp $CFG_DEFAULT $CFG_RUNNING
    fi
fi
sort $CFG_RUNNING | tr -d "\r" > $CFG_SYSTEM
cp $CFG_SYSTEM $CFG_RUNNING

# But for DFS testing, it's useful to be able to overide this
if [ -f /etc/persistent/enable_printk ]; then
    echo 9 > /proc/sys/kernel/printk
    dmesg -c
else
    # Do not clutter serial port, normally
    echo 1 > /proc/sys/kernel/printk
fi;

# Set device date to firmware build date
BDATE=201509091722
if [ ! -z $BDATE ]; then
    date -s $BDATE >/dev/null 2>&1
fi

# Run configuration parser
if [ -e /sbin/ubntconf ]; then
    /sbin/ubntconf
    echo "ubntconf returned $?" >> /tmp/ubntconf.log
fi

echo "...running /sbin/init"
exec /sbin/init

echo "INTERNAL ERROR!!! Cannot run /sbin/init."

这篇关于linuxrc的用途是什么,rootfs需要它吗?的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持!

06-14 00:40