16GB的云服务器，只有14.9GB能用？4GB的只有3.32GB?

就算是按1000来算

4GB的为4000/1024=3.9GB，160000/1024=15.625GB

其他内存哪里了？

查看一下内存，的确是16GB的

另外一台也的确是4GB的

那其他空间哪里去了呢？

肯定是预留了：kdump空间的预留

修改

vi  /etc/default/grub

文件如下：

# If you change this file, run 'update-grub' afterwards to update
# /boot/grub/grub.cfg.
# For full documentation of the options in this file, see:
#   info -f grub -n 'Simple configuration'

GRUB_DEFAULT=0
GRUB_TIMEOUT_STYLE=hidden
GRUB_TIMEOUT=0
GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
GRUB_CMDLINE_LINUX_DEFAULT=""
GRUB_CMDLINE_LINUX="net.ifnames=0 biosdevname=0 console=ttyS0,115200 console=tty0 panic=5 intel_idle.max_cstate=1 intel_pstate=disable processor.max_cstate=1 crashkernel=2G-16G:512M,16G-:768M"

# Uncomment to enable BadRAM filtering, modify to suit your needs
# This works with Linux (no patch required) and with any kernel that obtains
# the memory map information from GRUB (GNU Mach, kernel of FreeBSD ...)
#GRUB_BADRAM="0x01234567,0xfefefefe,0x89abcdef,0xefefefef"

# Uncomment to disable graphical terminal (grub-pc only)
#GRUB_TERMINAL=console

# The resolution used on graphical terminal
# note that you can use only modes which your graphic card supports via VBE
# you can see them in real GRUB with the command `vbeinfo'
#GRUB_GFXMODE=640x480

# Uncomment if you don't want GRUB to pass "root=UUID=xxx" parameter to Linux
#GRUB_DISABLE_LINUX_UUID=true

# Uncomment to disable generation of recovery mode menu entries
#GRUB_DISABLE_RECOVERY="true"

# Uncomment to get a beep at grub start
#GRUB_INIT_TUNE="480 440 1"

注意这里

crashkernel=2G-16G:512M,16G-:768M

两到十六GB，留下512MB，16GB以上则留下768。

这系统内核的错误，我这么穷，我还管啥。

我直接复制一行，然后删除掉crashkernel=2G-16G:512M,16G-:768M

sudo grub-mkconfig -o /boot/grub/grub.cfg

让配置生效，然后重启

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