Oracle, Linux, AWS, Azure, GCP
June 15, 2022 Leave a comment
After installing/starting the tiger VNC server, and connecting using VNC Viewer terminal window is not displayed.
# yum install tigervnc-server
Install xterm:
# yum install xterm
Kill old VNC process and start again:
$ vncserver -kill :1
$ vncserver -geometry 1024x1024
Reconnect using VNC viewer, terminal should be displayed automatically.
April 21, 2022 Leave a comment
There are several ways to do that, I found the simplest (I hope so) and want to share it with you:
0. Create repo file:
# vi /etc/yum.repos.d/google-chrome.repo [google-chrome] name=google-chrome baseurl=https://dl.google.com/linux/chrome/rpm/stable/x86_64 enabled=1 gpgcheck=1 gpgkey=https://dl.google.com/linux/linux_signing_key.pub
1. Enable repo ol7_optional_latest for vulkan dependency:
# yum-config-manager --enable ol7_optional_latest
2. Install google-chrome-stable package:
# yum install google-chrome-stable -y
3. Run:
$ google-chrome
Or in the background:
$ google-chrome &
The window will come up in VNC or X Window whichever you’ve configured before.
March 22, 2022 Leave a comment
There are several ways to fulfill the same task, I am providing one of them.
# uname -r 5.4.17-2036.101.2.el7uek.x86_64
2. Find all available kernels in your system and locate their index number:
# grubby --info=ALL index=0 kernel=/boot/vmlinuz-5.4.17-2036.101.2.el7uek.x86_64 args="ro console=tty1 console=ttyS0,115200n8 earlyprintk=ttyS0,115200 rootdelay=300 numa=off transparent_hugepage=never net.ifnames=0" root=/dev/mapper/rootvg-rootlv initrd=/boot/initramfs-5.4.17-2036.101.2.el7uek.x86_64.img title=Oracle Linux Server 7.9, with Unbreakable Enterprise Kernel 5.4.17-2036.101.2.el7uek.x86_64 index=1 kernel=/boot/vmlinuz-3.10.0-1160.42.2.el7.x86_64 args="ro console=tty1 console=ttyS0,115200n8 earlyprintk=ttyS0,115200 rootdelay=300 numa=off transparent_hugepage=never net.ifnames=0" root=/dev/mapper/rootvg-rootlv initrd=/boot/initramfs-3.10.0-1160.42.2.el7.x86_64.img title=Oracle Linux Server 7.9, with Linux 3.10.0-1160.42.2.el7.x86_64 index=2 kernel=/boot/vmlinuz-0-rescue-d3dd3af16fd242cebb997c6041d68ad3 args="ro console=tty1 console=ttyS0,115200n8 earlyprintk=ttyS0,115200 rootdelay=300 numa=off transparent_hugepage=never net.ifnames=0" root=/dev/mapper/rootvg-rootlv initrd=/boot/initramfs-0-rescue-d3dd3af16fd242cebb997c6041d68ad3.img
3. Check currently loaded kernel index using grubby tool (actually, we could find the same from 1st and 2nd steps, but let’s do one more time):
# grubby --default-index 0
4. Change the default kernel, in my case I want to set it to vmlinuz-3.10.0-1160.42.2.el7.x86_64 and it’s index number is 1:
# grubby --set-default 1
5. Reboot the system and check the kernel again:
# reboot # uname -r 3.10.0-1160.42.2.el7.x86_64
December 17, 2021 Leave a comment
Yes, it can be changed without impacting the business operations.
Oracle source: Doc ID 2269728.1
RHEL source: https://access.redhat.com/solutions/437043
========================Additional information========================
Additional explanation, why you may need to change that value.
Alert log shows:
ORA-27090: Unable to reserve kernel resources for asynchronous disk I/O Linux-x86_64 Error: 2: No such file or directory Additional information: 3 Additional information: 128 Additional information: 139817340277512
The problem is caused by a lower than recommended value for aio-max-nr. The current value is 1048576, but recommended is 3145728.
Set fs.aio-max-nr to 3145728 in /etc/sysctl.conf.
# grep fs.aio-max-nr /etc/sysctl.conf fs.aio-max-nr = 3145728
Make a new value effective:
# sysctl -p /etc/sysctl.conf
Verify the new value:
# sysctl -a|grep fs.aio-max-nr fs.aio-max-nr = 3145728
May 20, 2021 4 Comments
Problem:
After checking if flashgrid-clan package was installed, got this error:
error: rpmdb: BDB0113 Thread/process 2884/140438918064192 failed: BDB1507 Thread died in Berkeley DB library
error: db5 error(-30973) from dbenv->failchk: BDB0087 DB_RUNRECOVERY: Fatal error, run database recovery
error: cannot open Packages index using db5 - (-30973)
error: cannot open Packages database in /var/lib/rpm
error: rpmdb: BDB0113 Thread/process 2884/140438918064192 failed: BDB1507 Thread died in Berkeley DB library
error: db5 error(-30973) from dbenv->failchk: BDB0087 DB_RUNRECOVERY: Fatal error, run database recovery
error: cannot open Packages database in /var/lib/rpm
package flashgrid-clan is not installed
Reason:
If you see rpmdb errors during package management (rpm, yum), it means that the RPM database is corrupted.
Solution:
# mkdir /var/lib/rpm/backup # cp -a /var/lib/rpm/__db* /var/lib/rpm/backup/ # rm -f /var/lib/rpm/__db.[0-9][0-9]* # rpm --quiet -qa # rpm --rebuilddb # yum clean all
May 9, 2021 Leave a comment
I have used this command many times, but the interval between each usage is so big that I almost always forget the syntax.
So here it is:
# du -a / | sort -n -r | head -n 5 51190272 / 37705424 /root 33040524 /root/apache-tomcat-7.0.53 32802516 /root/apache-tomcat-7.0.53/logs 32802440 /root/apache-tomcat-7.0.53/logs/catalina.out
January 19, 2021 Leave a comment
Life is too short, that’s why it’s mandatory to use shortcuts… Instead of typing frequently used ssh client options such as port, user, hostname, identity-file and so on, you can save that information in sshd config file and then access it with defined alias.
/etc/ssh/ssh_config~/.ssh/config same as $HOME/.ssh/configInstead of connecting to the server everytime using the following command:
# ssh root@95.80.12.10 -i ~/.ssh/my_id_rsa
Save the following entries in ~/.ssh/config file:
# vim ~/.ssh/config
Host my_db
HostName 95.80.12.10
IdentityFile ~/.ssh/my_id_rsa
User root
And connect to the server using this simple way:
# ssh my_db
For other options check https://linuxize.com/post/using-the-ssh-config-file/
August 1, 2020 Leave a comment
There are several ways to identify that, I will suggest one of them using rpm -qf, that finds out what package a file belongs to:
Oracle Linux:
# rpm -qf /etc/redhat-release
oraclelinux-release-7.8-1.0.7.el7.x86_64
RHEL:
# rpm -qf /etc/redhat-release
redhat-release-server-7.8-2.el7.x86_64
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