今天yum update 我的一台 CentOS 7 服务器无法使用：启动时内核崩溃。我尝试从 GRUB 启动以前的内核，但它们都以同样的方式崩溃。我甚至尝试安装最新的 4.1 内核，它也崩溃了
kernel panic-not syncing: VFS: unable to mount root fs
但有一个例外：GRUB 上的最后一行是“救援内核”。这个启动正常，我可以在控制台上登录（没有显示任何错误消息）。
我尝试重新安装内核（yum reinstall kernel，yum remove kernel ; yum update） - 同样崩溃。 还剩下大约 200 MB /boot。
我应该怎么做？（除了重新安装操作系统）
编辑：评论后提供进一步信息
这是一台物理机器，文件系统未加密
# rpm -qa kernel
kernel-3.10.0-123.13.2.el7.x86_64
kernel-3.10.0-229.7.2.el7.x86_64
# df -T
Filesystem Type 1K-blocks Used Available Use% Mounted on
/dev/mapper/vg_euextscan-lv_root ext4 51475068 17826932 31010312 37% /
devtmpfs devtmpfs 16347896 0 16347896 0% /dev
tmpfs tmpfs 16367276 0 16367276 0% /dev/shm
tmpfs tmpfs 16367276 16932 16350344 1% /run
tmpfs tmpfs 16367276 0 16367276 0% /sys/fs/cgroup
/dev/sda1 ext4 487652 179742 278214 40% /boot
/dev/mapper/vg_euextscan-lv_home ext4 507841520 11176144 470845424 3% /home
# vgdisplay
--- Volume group ---
VG Name vg_euextscan
System ID
Format lvm2
Metadata Areas 1
Metadata Sequence No 4
VG Access read/write
VG Status resizable
MAX LV 0
Cur LV 3
Open LV 3
Max PV 0
Cur PV 1
Act PV 1
VG Size 557.88 GiB
PE Size 4.00 MiB
Total PE 142818
Alloc PE / Size 142818 / 557.88 GiB
Free PE / Size 0 / 0
VG UUID JOZX35-8T48-Yd10-wcta-wfSR-Fpf0-Hfkk1S
cat /boot/grub/grub.conf
# grub.conf generated by anaconda
#
# Note that you do not have to rerun grub after making changes to this file
# NOTICE: You have a /boot partition. This means that
# all kernel and initrd paths are relative to /boot/, eg.
# root (hd0,0)
# kernel /vmlinuz-version ro root=/dev/mapper/vg_euextscan-lv_root
# initrd /initrd-[generic-]version.img
#boot=/dev/sdb
default=0
timeout=5
splashimage=(hd0,0)/grub/splash.xpm.gz
hiddenmenu
title CentOS Linux (3.10.0-229.7.2.el7.x86_64) 7 (Core)
root (hd0,0)
kernel /vmlinuz-3.10.0-229.7.2.el7.x86_64 ro root=/dev/mapper/vg_euextscan-lv_root rd_NO_LUKS KEYBOARDTYPE=pc KEYTABLE=fr LANG=en_US.UTF-8 rd_NO_MD SYSFONT=latarcyrheb-sun16 crashkernel=auto rd_LVM_LV=vg_euextscan/lv_swap rd_LVM_LV=vg_euextscan/lv_root rd_NO_DM rhgb quiet
title CentOS Linux (4.1.0-1.el7.elrepo.x86_64) 7 (Core)
root (hd0,0)
kernel /vmlinuz-4.1.0-1.el7.elrepo.x86_64 ro root=/dev/mapper/vg_euextscan-lv_root rd_NO_LUKS KEYBOARDTYPE=pc KEYTABLE=fr LANG=en_US.UTF-8 rd_NO_MD SYSFONT=latarcyrheb-sun16 crashkernel=auto rd_LVM_LV=vg_euextscan/lv_swap rd_LVM_LV=vg_euextscan/lv_root rd_NO_DM rhgb quiet
title CentOS Linux (3.10.0-123.13.2.el7.x86_64) 7 (Core)
root (hd0,0)
kernel /vmlinuz-3.10.0-123.13.2.el7.x86_64 ro root=/dev/mapper/vg_euextscan-lv_root rd_NO_LUKS KEYBOARDTYPE=pc KEYTABLE=fr LANG=en_US.UTF-8 rd_NO_MD SYSFONT=latarcyrheb-sun16 crashkernel=auto rd_LVM_LV=vg_euextscan/lv_swap rd_LVM_LV=vg_euextscan/lv_root rd_NO_DM rhgb quiet
initrd /initramfs-3.10.0-123.13.2.el7.x86_64.img
title CentOS Linux 7 Rescue 3df14aca2793db41f468b5f800000019 (3.10.0-123.9.2.el7.x86_64)
root (hd0,0)
kernel /vmlinuz-0-rescue-3df14aca2793db41f468b5f800000019 ro root=/dev/mapper/vg_euextscan-lv_root rd_NO_LUKS KEYBOARDTYPE=pc KEYTABLE=fr LANG=en_US.UTF-8 rd_NO_MD SYSFONT=latarcyrheb-sun16 crashkernel=auto rd_LVM_LV=vg_euextscan/lv_swap rd_LVM_LV=vg_euextscan/lv_root rd_NO_DM rhgb quiet
initrd /initramfs-0-rescue-3df14aca2793db41f468b5f800000019.img