Pythian Blog: Technical Track

Quick Tip : Oracle User Ulimit Doesn’t Reflect Value on /etc/security/limits.conf

by Rene Antunez on May 4, 2015 12:00:00 AM

So the other day I was trying to do a fresh installation of a new Oracle EM12cR4 in a local VM, and as I was doing it with the DB 12c, I decided to use the Oracle preinstall RPM to ease my installation of the OMS repository database. Also I was doing both the repository and EM12c OMS install in the same VM, that is important to know. [code language="bash"] [root@em12cr4 ~]# yum install oracle-rdbms-server-12cR1-preinstall -y [/code] I was able to install the DB without any issues, but when I was trying to do the installation of EM12cR4, an error in the pre-requisites popped up:
WARNING: Limit of open file descriptors is found to be 1024. For proper functioning of OMS, please set “ulimit -n” to be at least 4096.
And if I checked the soft limit for the user processes , it was set to 1024: [code language="bash"] oracle@em12cr4.localdomain [emrep] ulimit -n 1024 [/code] So if you have been working with Oracle DBs for a while you know that this has to be checked and modified in /etc/security/limits.conf , but it was my surprise that the limit has been set correctly for the oracle user to at least 4096: [code language="bash"] [root@em12cr4 ~]# cat /etc/security/limits.conf | grep -v "#" | grep nofile oracle soft nofile 4096 oracle hard nofile 65536 [/code] So my next train of thought was to verify the user bash profile settings, as if the ulimits are set there, it can override the limits.conf, but again it was to my surprise that there was nothing in there, and that is were I was perplexed: [code language="bash"] [oracle@em12cr4 ~]# cat .bash_profile # .bash_profile # Get the aliases and functions if [ -f ~/.bashrc ]; then . ~/.bashrc fi # User specific environment and startup programs PATH=$PATH:$HOME/bin export PATH [/code] So what I did next was open a root terminal and do a trace of the login of the Oracle user: [code language="bash"] [root@em12cr4 ~]# strace -o loglimit su - oracle [/code] And in another terminal was verify what was the user reading regarding the user limits, and this is where I hit the jackpot. I was able to see here that it was reading the pam_limits.so and the /etc/security/limits.conf as it should, but it was also reading another configuration file called oracle-rdbms-server-12cR1-preinstall.conf, (Does this look familiar to you ? :) ) and as you can see the RLIMIT_NOFILE was being set to 1024: [code language="bash"] [root@em12cr4 ~]# grep "limit" loglimit getrlimit(RLIMIT_STACK, {rlim_cur=10240*1024, rlim_max=32768*1024}) = 0 open("/lib64/security/pam_limits.so", O_RDONLY) = 6 ... open("/etc/security/limits.conf", O_RDONLY) = 3 read(3, "# /etc/security/limits.conf\n#\n#E"..., 4096) = 2011 open("/etc/security/limits.d", O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC) = 3 open("/etc/security/limits.d/90-nproc.conf", O_RDONLY) = 3 read(3, "# Default limit for number of us"..., 4096) = 208 open("/etc/security/limits.d/oracle-rdbms-server-12cR1-preinstall.conf", O_RDONLY) = 3 setrlimit(RLIMIT_STACK, {rlim_cur=10240*1024, rlim_max=32768*1024}) = 0 setrlimit(RLIMIT_NPROC, {rlim_cur=16*1024, rlim_max=16*1024}) = 0 setrlimit(RLIMIT_NOFILE, {rlim_cur=1024, rlim_max=64*1024}) = 0 [/code] So I went ahead and checked the file /etc/security/limits.d/oracle-rdbms-server-12cR1-preinstall.conf and evidently, that is where the limit was set to 1024, so the only thing I did was change the value there to 4096: [code language="bash"] [root@em12cr4 ~]# cat /etc/security/limits.d/oracle-rdbms-server-12cR1-preinstall.conf | grep -v"#" | grep nofile oracle soft nofile 1024 oracle hard nofile 65536 [root@em12cr4 ~]# vi /etc/security/limits.d/oracle-rdbms-server-12cR1-preinstall.conf [root@em12cr4 ~]# cat /etc/security/limits.d/oracle-rdbms-server-12cR1-preinstall.conf | grep -v"#" | grep nofile oracle soft nofile 4096 oracle hard nofile 65536 [/code] Once I did that change, and logged out and logged back in, I was able to see the values that I had set in the first place in /etc/security/limits.conf and now I was able to proceed with the installation of EM12cR4: [code language="bash"] oracle@em12cr4.localdomain [emrep] ulimit -n 4096 [/code] Conclusion So when you install the RPM oracle-rdbms-server-12cR1-preinstall, be sure that if you are to change any future user limits, there might be another configuration file that can be setting other values than the ones desired and set in /etc/security/limits.conf Note.- This was originally published in rene-ace.com

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