How to check CPU information in Linux

CPU information explains why one Linux host exposes a different instruction set, core layout, or virtual CPU shape than another. That matters when checking software compatibility, sizing virtual machines, or confirming that the kernel can see the processor resources that firmware or the hypervisor should expose.

lscpu reads processor data from kernel interfaces such as /proc/cpuinfo and /sys and formats it as one readable summary plus optional topology tables. The summary shows architecture, logical CPU count, vendor or implementer details, thread and core layout, cache lines, and any kernel-reported vulnerability entries that the running platform publishes.

The command flow was verified on a current Ubuntu 24.04 LTS ARM64 environment, which reports cluster topology and leaves some x86_64-style fields blank. Virtual machines, containers, and some ARM64 systems can legitimately show - for Model name, Socket(s), or NUMA node(s), so the populated fields matter more than any single blank line.

1. Open a terminal.
2. Display the full processor summary with lscpu.

   $ lscpu
   Architecture:                            aarch64
   CPU op-mode(s):                          64-bit
   Byte Order:                              Little Endian
   CPU(s):                                  10
   On-line CPU(s) list:                     0-9
   Vendor ID:                               Apple
   Model name:                              -
   Model:                                   0
   Thread(s) per core:                      1
   Core(s) per cluster:                     10
   Socket(s):                               -
   Cluster(s):                              1
   Flags:                                   fp asimd evtstrm aes pmull sha1 sha2 crc32 atomics fphp asimdhp cpuid asimdrdm jscvt fcma lrcpc dcpop sha3 asimddp sha512 asimdfhm dit uscat ilrcpc flagm sb paca pacg dcpodp flagm2 frint
   Vulnerability Gather data sampling:      Not affected
   Vulnerability Indirect target selection: Not affected
   ##### snipped #####

   The summary is the quickest single view of architecture, logical CPU count, vendor or implementer, topology, instruction flags, and vulnerability status.

3. Show each logical CPU and the topology fields that the kernel currently exports.

   $ lscpu --extended=cpu,core,socket,node,online
   CPU CORE SOCKET NODE ONLINE
     0    0      0    -    yes
     1    1      0    -    yes
     2    2      0    -    yes
     3    3      0    -    yes
     4    4      0    -    yes
     5    5      0    -    yes
     6    6      0    -    yes
     7    7      0    -    yes
     8    8      0    -    yes
     9    9      0    -    yes

   Named columns keep the table predictable. Unsupported topology fields stay in the output and show - instead of silently disappearing.

4. Print the same topology data in parse-friendly form when it needs to be pasted into notes or read by another tool.

   $ lscpu --parse=cpu,core,socket,node,online
   # The following is the parsable format, which can be fed to other
   # programs. Each different item in every column has an unique ID
   # starting usually from zero.
   # CPU,Core,Socket,Node,Online
   0,0,0,,Y
   1,1,0,,Y
   2,2,0,,Y
   3,3,0,,Y
   4,4,0,,Y
   ##### snipped #####

   The parse format keeps one logical CPU per line and avoids the spacing changes that a terminal-friendly table can introduce.

5. Match the reported layout to the platform before treating blank fields as a problem.

   x86_64 systems often show Model name and Core(s) per socket, while current ARM64 systems can report Core(s) per cluster and leave Socket(s) blank. In guests and containers, the result describes the CPU layout exposed to that environment rather than the physical host.