29
votes
2answers
1k views

Why did powering down my machine after a bad `rm` save my files?

Classical situation: I ran a bad rm and realized immediately afterwards that I had removed the wrong files. (Nothing critical and I had tolerably recent backups, but still annoying.) Knowing that ...
0
votes
1answer
26 views

to print address space of a process in ubuntu 12.04

How do I print an address space of a process by taking the process' PID?
1
vote
1answer
43 views

How logical address of one process differs from the logical address of another?

I am a newbie. I am reading Understanding Linux Kernel. There, I am trying to understand how logical address got translated to physical address. To my understanding, I believe logical address got ...
2
votes
0answers
52 views

Virtual kernel memory layout in dmesg linux kernel 2.6.31

I'm working on a embedded linux project for ARM architecture, kernel version is 2.6.31.12-rt21. In dmesg, I cannot see the virtual kernel memory layout like this: virtual kernel memory layout: ...
1
vote
1answer
120 views

How does the kernel know how much user addressable memory to set aside?

I was reading up on a rather-dated article on the kernel managing memory and had this question on where the Page Table Entries (PTE) would go into. For this example, the author assumes we are on a ...
-1
votes
1answer
40 views

get Various types of address used [closed]

How to get various address ranges of a running machine or a crash dump? User virtual address Physical address Bus address Kernel logical address Kernel virtual address I don't need the bus ...
7
votes
3answers
4k views

Why is the theoretical RAM limit for RHEL 6 128 TB and how is this determined?

I'm studying for RHCSA and am confused by a statement I came across in some training material: There is no practical maximum RAM, as theoretically, you could run 128 TB of RAM on RHEL 6. But ...
1
vote
0answers
420 views

Where does the Linux kernel reside in memory ?

From some book I have, I have in my notes that the Linux kernel resides at 0xc00000000 on 32-bit systems, and is mapped into user space for performance reasons. Is this accurate ? How can I verify ...
2
votes
1answer
1k views

How to debug Linux kernel panic?

I am trying to debug a kernel panic. Panic message says unable to handle kernel paging request for address 40025694. At the time of panic it was executing ldreq r10, [lr, #-4] @ get SWI instruction. ...
7
votes
2answers
1k views

An oom killer thats baffling me

I am not able to understand why would kernel issue this oom killer when I see enough memory is available: Also why are there so many kernel cache pages allocated? I say enough memory is available ...
3
votes
0answers
584 views

How extended (4MB) and regular (4KB) paging coexist?

On x86 architecture, "Extended paging" allows page frames (physical memory) to be 4 MB instead of 4 KB. The book "Understanding the Linux Kernel, 3rd" at chapter 2 "Memory Addressing", sub-chapter ...
1
vote
2answers
488 views

NAND flash memory wear & virtual memory page swap

For a linux kernel with virtual memory and disk storage, pages are swapped back and forth into swap area. But embedded systems generally use NAND flash instead of disk. A NAND flash has a limited ...