Linux Questions 6

Member_2_6368962 used Ask the Experts™
Hi everybody,

I am completing a Linux test and I would like to know if someone is good at linux OS and could anwer theses questions for me to compare.

10- User is running a process, but it seems to be stuck, when attaching strace to the pid, strace shows an unfinished system call.

10.1- What is the meaning of an unfinished syscall?

10.2- What is the best approach to understand what is happening in this process?

10.3- How can one tell exactly where the process is stuck, or how to debug the problem further?

11- User is running a process, but it seems to be stuck, when attaching strace to the pid, strace shows nothing at all.

11.1- how can one understand what is happening and the status of the process?

11.2- What can one do to debug this case even further?

12- Superuser runs 'sync' on a linux system, but this command never returns, doing 'ps auxw | grep sync' the sysadmin notices that it is in 'D' state. Can the sysadmin kill this process? The sysadmin tried to strace the process, which only showed the unfinished sync() syscall.

Supposing that a support call will be opened to find the root cause of this issue, what kind of information would you try to obtain, and why?

13- By accident a sysadmin removed one of the disks belonging to an active VG. When rebooting the system they notice that the system does not boot anymore. The disk that was removed was part of the VG but contained no data. What is the procedure to bring the machine back to operation and the VG back with its LVs?

14- Write a shell command that lists all the RPMs installed in a system sorted by package size, largest package first (use dpkg and related commands if you're not familiar with RPM and related commands)

15-  A sysadmin just added a new TAPE drive to his system. The system already had a drive called /dev/st0, which works fine. The sysadmin added the tape drive and created a /dev/st1 for it:

# ls -l /dev/st1
brw-r--r-- 1 root root 8, 1 Mar  2 23:16 /dev/st1

The sysadmin loads a tape into the drive and runs a dd, to write his 3G file onto it, which should fit as the tape supports 200Gb.

# dd if=/tmp/backup.tar of=/dev/st1 bs=32k

However the dd finishes with an error saying that the device is full at 250Mb.

15.1- Is it a problem caused by the block size of the dd? Are there any situations where the block size used can change the behaviour of a drive?

15.2- Can you explain why this is not working as expected?

15.3- The sysadmin rebooted the system, and now the boot loader is not working properly, and GRUB complains about a problem at stage 1.5. What should one do?

Thank you very much
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Gerwin Jansen, EE MVETopic Advisor
Most Valuable Expert 2016
Asking questions this way is against EE-rules I'm afraid.
Technology and Business Process Advisor
Most Valuable Expert 2013
We cannot answer your homework questions or test questions for you.  We CAN GUIDE you in what you do know and explain why you are correct or why you might be incorrect if you post YOUR answers to these questions.  Helping you understand is not a problem - doing the work for you is.

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