I installed Ubuntu Server on an older Lenovo H500s desktop with an Intel Pentium J2900 processor. It worked normally for a while, but then stopped booting and began showing messages such as "watchdog: BUG: soft lockup - CPU#3 stuck for 325s!" Ubuntu now hangs during startup, including when I boot a fresh installer USB. Standard updates and BIOS checks have not helped, and Windows still runs successfully on the machine. The system has a quad-core J2900, and I'm currently trying to install Ubuntu Server 26.04 with a 7.0 kernel. What can I try to get Ubuntu installed and running again?
2 Answers
Since Windows works and the lockup happens even from a newly created USB, this points more toward a kernel or hardware-compatibility problem than a damaged installation, root partition, or swap setup. Try an older supported Ubuntu LTS release with its older kernel, and test the installer’s safe graphics or compatibility options. If an older kernel boots reliably, install that version first and upgrade cautiously rather than starting with the newest release.
The Pentium J2900 is an older Bay Trail chip, and some Linux kernels have trouble with its power-management states. At the Ubuntu boot menu, press **e**, find the line beginning with `linux`, and append `intel_idle.max_cstate=1` before booting. If that works, add the same option to the installed system’s GRUB configuration later. You can also try disabling CPU C-states in the firmware if that option is available.
I’ll try the `intel_idle.max_cstate=1` boot option first and compare it with an older Ubuntu LTS installer.