KB-7528: How to Modify the oom_adj Score of PuTTY Shell When Using Centrify OpenSSH

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KB-7528: How to Modify the oom_adj Score of PuTTY Shell When Using Centrify OpenSSH

Product:

Authentication Service ,

Published:

28 September,16 at 11:41 PM

Rating:

Applies to:

Centrify Server Suite 2016 and later

Question:

The oom_adj (Out Of Memory) score is used by the operating system when the machine is low on memory. The score determines the risk involved in terminating a process to free up memory. A higher score means that the process is MORE likely to be terminated.

When a shell in opened through a PuTTY login to a Centrified CentOS 6.2 machine, the resulting oom_adj of that process is -17. The cause for concern is that the -17 would mean that the process would not be terminated. If there are say 100 users that are using a process that cannot be terminated, and the system might go into panicked mode.

To determine the current oom_adj score

1) Ensure Centrify OpenSSH is running

2) Launch PuTTY and connect to the CentOS machine

3) When the shell opens, find the process ID by entering this command:

$ echo $$
13772

4) Change to the process directory for this specific shell and check the oom_adj file

$ cd /proc/13772 (where 13772 is the Proc id from the echo in step 3)
$ cat oom_adj

5) Observe that the score is -17. For comparison, repeat these steps when stock sshd is running and observe that the score is 0.

How can the oom_adj score be modified to 0 so it is the same value used by stock SSHD?

Answer:

1) Logon to the Centrified machine as root and edit the file /etc/init/centrify-sshd.conf .

2) Find the line which reads 'oom never' and place a hash mark at the beginning of the line, as in the image below: