Tag: Linux

Fix “ORA-03114: not connected to ORACLE” error

I utilize docker-oracle12c to run Oracle in docker, and bind specified CPU and memory:

docker run -d -it --cpuset-cpus=xx-xx,xx-xxx  --cpuset-mems=x,x ...

All containers run OK but one Oracle database is always created failed, and the error log is:

ORA-03114: not connected to ORACLE

After tough debugging, the reason is the memory on specified NUMA node is not enough:

# numactl -H
......
node 2 size: 786432 MB
node 2 free: xxxxx MB

node 3 size: 786432 MB
node 3 free: xxxxx MB

The solution is disable HugePages temporarily:

# cat /etc/sysctl.conf
......
vm.nr_hugepages=0
......
# sysctl -p

After creating database, enable HugePages again:

# cat /etc/sysctl.conf
......
vm.nr_hugepages=xxxxxx
......
# sysctl -p

 

Upgrade Linux kernel on RHEL 7

My OS is RHEL 7.2 (minimal installation version). To use some new kernel features (such as BPF), I need to upgrade kernel to 4.x.

(1) Register the system and apply a subscription:

# subscription-manager register --username <username> --password <password> --auto-attach

(2) Use yum install to install the following software packages:

openssl-devel
ncurses-devel
bc
gcc
perl

BTW, when executing yum install perl, it prompts errors, so I download the source code from perl official website, and build it form scratch:

./configure.gnu
make 
make test
make install

(3) Download the stable kernel from kernel.org and extract it, then build it:

make menuconfig
make 
make modules_install install

According to your requirement, maybe installing the header files is also need:

make INSTALL_HDR_PATH=/usr/local headers_install

(4) Reboot system, and select right kernel on boot time, enjoy it:

# uname -a
Linux localhost.localdomain 4.5.0 #1 SMP Mon Apr 11 09:56:46 EDT 2016 x86_64 x86_64 x86_64 GNU/Linux

 

How to count the line number of a file?

How to count the line number of a file? It seems an easy question for Unix guys: using wc command. Let’s see an example:

# cat test
aaaa
bbbb
cccc
# wc -l test
3 test

It displays right. But wait a minute, let’s check the wc -l option meaning:

# wc --help
......
-l, --lines            print the newline counts
......

wc -l just print the newline counts, so it increases newline count as the line number. Using hexdump to see the content of test:

# hexdump -C test
00000000  61 61 61 61 0a 62 62 62  62 0a 63 63 63 63 0a     |aaaa.bbbb.cccc.|
0000000f

No problem, test contains 3 newlines. But now, the question is here, how about the last line doesn’t contain newline?

Let me do the following experiment:

# echo -n "a" > test
# hexdump -C test
00000000  61                                                |a|
00000001
# wc -l test
0 test

Now the test file only contains 1 character, and no newline. This time, wc -l thinks there is no line in test file.

Based on the previous discussion, maybe awk is a better tool when using to count line number of file. Just one statement:

# awk 'END {print NR}' test
1

It outputs right line number.

SELinux cause “Permission denied” issue in using docker

I am using docker on RHEL 7. After mounting host directory into container, some interesting things happen: Although I am a root user, and seem to have all permissions, but the system will prompt “Permission denied” when executing commands:

# docker run -v /root:/test --rm -it debian ls /test
ls: cannot open directory /test: Permission denied

Through tough investigations, I find the root cause is about SELinux:

# sestatus
SELinux status:                 enabled
SELinuxfs mount:                /sys/fs/selinux
SELinux root directory:         /etc/selinux
Loaded policy name:             targeted
Current mode:                   enforcing
Mode from config file:          enforcing
Policy MLS status:              enabled
Policy deny_unknown status:     allowed
Max kernel policy version:      28

The current mode of SELinux is enforcing, and I get 2 solutions to resolve it now:

(1)

Add --privileged option in docker run command:

# docker run --privileged -v /root:/test --rm -it debian ls /test
Desktop    Pictures   anaconda-ks.cfg       linuxamd64_12102_database_1of2.zip
Documents  Public     database              linuxamd64_12102_database_2of2.zip
Downloads  Templates  docker-oracle12c      sysdig
Music      Videos     initial-setup-ks.cfg

(2)

Set SELinux mode as permissive:

# setenforce 0
# docker run -v /root:/test --rm -it debian ls /test
Desktop    Downloads  Pictures  Templates  anaconda-ks.cfg  docker-oracle12c      linuxamd64_12102_database_1of2.zip  sysdig
Documents  Music      Public    Videos     database         initial-setup-ks.cfg  linuxamd64_12102_database_2of2.zip

References:
Why does docker prompt “Permission denied” when backing up the data volume?;
Why does docker container prompt “Permission denied”?.

 

Fix “TNS-01106: Listener using listener name LISTENER has already been started” error

I utilize docker-oracle12c to run Oracle in docker. When starting listener, it outputs following:

$ lsnrctl start

LSNRCTL for Linux: Version 12.1.0.2.0 - Production on 25-FEB-2016 00:38:38

Copyright (c) 1991, 2014, Oracle.  All rights reserved.

TNS-01106: Listener using listener name LISTENER has already been started

I first meet TNS-01106 error, so try to use “lsnrctl status” to check the listener status:

$ lsnrctl status

LSNRCTL for Linux: Version 12.1.0.2.0 - Production on 25-FEB-2016 00:38:52

Copyright (c) 1991, 2014, Oracle.  All rights reserved.

Connecting to (ADDRESS=(PROTOCOL=tcp)(HOST=)(PORT=1521))
TNS-12541: TNS:no listener
 TNS-12560: TNS:protocol adapter error
  TNS-00511: No listener
   Linux Error: 2: No such file or directory

No listener is running, so what is wrong? After checking the configuration file, I find the file name is spelled wrongly as listerner.ora, not listener.ora! After modifying name, the “lsnrctl start” run successfully:

$ lsnrctl start

LSNRCTL for Linux: Version 12.1.0.2.0 - Production on 25-FEB-2016 00:41:25

Copyright (c) 1991, 2014, Oracle.  All rights reserved.

Starting /app/oracle/product/12.1.0/dbhome_1/bin/tnslsnr: please wait...
......

P.S. If there are some configuration errors in listerner.ora, such as port number, host address, it also induce this error.