Unix/Linux

Last week, got this issue reported by a DBA that he wasn’t able to su to oracle user from root on a Oracle Base Database VM in OCI. The login of opc user worked fine and he could do sudo su to root but he couldn’t su to oracle. When he did it just came back to root shell. [root@xxx ~]# su - oracle Last login: Fri Jan 12 10:20:38 UTC 2023 [root@xxx ~]# There was nothing relevant in /var/log/messages or /var/log/secure. I tried it for some other user and it worked fine. Then I suspected something with the profile of oracle user and voila ! The .bashrc looked like this ...

A customer who is using an Exadata X8M-2 with multiple VMs had Smokescreen deployed in their company recently and they reported an issue that one of the Smokescreen decoy servers in their DC was seeing traffic from one of the Exadata VMs on a certain port. That was rather confusing as that port was the database listener port on that VM and why would a VM with Oracle RAC deployed try to access any random IP on the listener port. Also it was happening only for this VM. Nothing for so many other VMs. ...

Scenario : Setting up a physical standby from Exadata to a non-Exadata single instance. tnsping from standby to primary works fine but tnsping from primary to standby fails with: [sql]TNS-12543: TNS:destination host unreachable[/sql] I am able to ssh standby from primary, can ping as well but tnsping doesn’t work. From the error description we can figure out that something is blocking the access. In this case it was iptables that was enabled on the standby server. ...

One of my friend today asked me about removing Linux partitions & GRUB (from a dual boot system) and return back to windows alone. Removing Linux involves just formatting/removing the partitions. Now to remove GRUB either do fdisk /mbr from a Windows 98 bootable CD or do fixmbr after booting into repair mode with Windows XP CD. But if you have none then to remove GRUB you will need some utility like this one and if you reboot before doing that it might make GRUB unable to boot into Windows. It will get stuck at GRUB> prompt only. So there is an option: to manually boot the OS you want (ie Windows). A quick search gave link to this thread. It involves few commands on the GRUB prompt: ...

If you are used to work in Unix enviroment and then sometime, in between have to sit on Windows and tail -f alert_DB.log, its a real pain. There is a small bundle of utilities, called Unxutils which can make you feel at home in Windows too. These are the exe’s of all major commands in Unix like more, less, ls, grep etc… To use it just download the zip file from the link above, extract it to some folder and add the path of exe’s to your Windows PATH. Restart your machine and you are done. ...

Last week I attended a training on AIX system administration from IBM (organized by company, obviously ;) It was a 7 days course covering all of the system administration stuff. There was a lot of new stuff to learn, LVM being the most number of times uttered word, once we did the chapter on LVM. It was a nice experience as a whole as for the first time I attended any training on Unix. ...

I was searching for some good tutorials on awk. Found a very nice (brilliant indeed) article on Oracle website by Emmett Dulaney. A very good introduction for beginners. I searched for some other links as well. Have a read: 1. AWK: The Linux Administrators’ Wisdom Kit 2. A Guided Tour Of Awk 3. AWK Programming 4. UNIX Utilities - awk Happy awk’ing :) Sidhu

I have been installing Linux for last 6 years and for more than half the number of times, came across a message something like “This partitions is beyond the 1024 cylinder boundary and may not be bootable”. But never cared for it much and understood what exactly it meant to say ? Yesterday I was reading System Admin guide to Linux by Lars Wirzenius (Thanks Howard for the link :) From there I came to know what exactly that message meant. Quoting from the guide itself: ...

If you are crazy@*nix, 2 really interesting posts about run levels in *nix No runlevels?? What is the use of runlevels? Sidhu

Sometimes, while installing Linux, installing LILO/GRUB to MBR makes you run into loads of issues, one of the most popular being that after reboot you are not able to boot into either of the OS ;) There is a way to use NTLDR to boot Linux, this way the MBR remains untouched and if you don’t want to see the Linux option, what you need to do is, edit your boot.ini and your are done. ...