ubuntu22 无法设置 4k 分辨率怎么办？

Question

前言：之前是 ubuntu20.04，安装 ubuntu20.04 的时候，用的还是 2k 显示器，所以就一直是 2k 分辨率，但是后来换了 4k 显示器之后，ubutu20 还是最高只能 2k，折腾了半天也设置不了 4k，后来就一直忍了！

但是后来因为，我安装的是双系统，win+ubuntu，我把 win 删了之后，ubuntu 就只能 768p 了，连 2k 都没有了。

一通操作之后，我只能升级到了 ubuntu22

---

原本是 ubuntu20.04 , 我通过 sudo do-release-upgrade 命令升级到了 ubuntu22.04

我通过设置 https://blog.csdn.net/u013764485/article/details/78007370 这个教程修改分辨率

╰─➤  cat /etc/default/grub
# 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=10
GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash nomodeset"
GRUB_CMDLINE_LINUX=""

# 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=1920x1080
GRUB_GFXPAYLOAD_LINUX=1920x1080


# 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"

设置为 1080P 可以正常显示

但是我改成 3840x2160,反而变成了 768P！

GRUB_GFXMODE=3840x2160
GRUB_GFXPAYLOAD_LINUX=3840x2160

xrandr 显示如下：

╰─➤  xrandr                   
xrandr: Failed to get size of gamma for output default
Screen 0: minimum 1920 x 1080, current 1920 x 1080, maximum 1920 x 1080
default connected primary 1920x1080+0+0 0mm x 0mm
   1920x1080     77.00* 

我的 CPU 是 amd5700g（没有配独立显卡，因为 amd5700g 只带了集成显卡vega8）

─➤  lscpu
架构：                   x86_64
  CPU 运行模式：         32-bit, 64-bit
  Address sizes:         48 bits physical, 48 bits virtual
  字节序：               Little Endian
CPU:                     16
  在线 CPU 列表：        0-15
厂商 ID：                AuthenticAMD
  型号名称：             AMD Ryzen 7 5700G with Radeon Graphics
    CPU 系列：           25
    型号：               80
    每个核的线程数：     2
    每个座的核数：       8
    座：                 1
    步进：               0
    Frequency boost:     enabled
    CPU 最大 MHz：       4673.0000
    CPU 最小 MHz：       400.0000
    BogoMIPS：           7585.66
    标记：               fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt pdpe1gb rdtscp lm cons
                         tant_tsc rep_good nopl nonstop_tsc cpuid extd_apicid aperfmperf rapl pni pclmulqdq monitor ssse3 fma cx16 sse4_1 sse4_2 movbe popcnt aes xsave avx f16
                         c rdrand lahf_lm cmp_legacy svm extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw ibs skinit wdt tce topoext perfctr_core perfctr_nb bpext p
                         erfctr_llc mwaitx cpb cat_l3 cdp_l3 hw_pstate ssbd mba ibrs ibpb stibp vmmcall fsgsbase bmi1 avx2 smep bmi2 erms invpcid cqm rdt_a rdseed adx smap clf
                         lushopt clwb sha_ni xsaveopt xsavec xgetbv1 xsaves cqm_llc cqm_occup_llc cqm_mbm_total cqm_mbm_local clzero irperf xsaveerptr rdpru wbnoinvd cppc arat
                          npt lbrv svm_lock nrip_save tsc_scale vmcb_clean flushbyasid decodeassists pausefilter pfthreshold avic v_vmsave_vmload vgif v_spec_ctrl umip pku osp
                         ke vaes vpclmulqdq rdpid overflow_recov succor smca fsrm
Virtualization features: 
  虚拟化：               AMD-V
Caches (sum of all):     
  L1d:                   256 KiB (8 instances)
  L1i:                   256 KiB (8 instances)
  L2:                    4 MiB (8 instances)
  L3:                    16 MiB (1 instance)
NUMA:                    
  NUMA 节点：            1
  NUMA 节点0 CPU：       0-15
Vulnerabilities:         
  Itlb multihit:         Not affected
  L1tf:                  Not affected
  Mds:                   Not affected
  Meltdown:              Not affected
  Mmio stale data:       Not affected
  Retbleed:              Not affected
  Spec store bypass:     Mitigation; Speculative Store Bypass disabled via prctl and seccomp
  Spectre v1:            Mitigation; usercopy/swapgs barriers and __user pointer sanitization
  Spectre v2:            Mitigation; Retpolines, IBPB conditional, IBRS_FW, STIBP always-on, RSB filling, PBRSB-eIBRS Not affected
  Srbds:                 Not affected
  Tsx async abort:       Not affected

主板是 微星的 B450M-MORTAR-MAX，链接： https://www.msi.com/Motherboa...

显示器是 dell 的 P2723 ，链接：https://item.jd.com/100050153...

Answer 1

问题已解决，重装系统就好了

之前是通过 ubuntu20 升级上来的，问题多到解决不了，索性重装为 ubuntu22

一切问题都消失了

Answer 2

在登录输入密码的界面，右下角有一个设置按钮，把Ubuntu换成Ubuntu on Xorg试试。