Cleaning Up Memory Usage
- May
- 06
- Posted by TKH Specialist
- Posted in System Administration
I noticed my Ubuntu desktop was using a rather large portion of available memory. I usually have a lot running on my system, multiple terminals, background jobs, etc so this is nothing unusual. Today however I noticed my system was sluggish so I started digging. Memory use was near 100%. I closed all of my […]
read morevi & vim aids
- Apr
- 10
- Posted by TKH Specialist
- Posted in System Administration
For my quick reference. To open two files in vi/vim and edit side by side (use CTRL-W + w to switch between the files): # vim -O foo.txt bar.txt To open a file and automatically move the cursor to a particular line number (for example line 80) # vi +80 ~/.ssh/known_hosts To display line numbers along the […]
read moreDenyhosts Assists
- Apr
- 10
- Posted by TKH Specialist
- Posted in Security, System Administration
Every so often a legitimate user will get blocked by deny hosts. When this happens you can re-enable their access with these 8 simple steps (UPDATE: or use the faster version, see below): Stop DenyHosts # service denyhosts stop Remove the IP address from /etc/hosts.deny Edit /var/lib/denyhosts/hosts and remove the lines containing the IP address. […]
read moreTesting Database Connectivity
- Mar
- 31
- Posted by TKH Specialist
- Posted in databases, System Administration
Working with databases and new application installations can be really fun. Problem is, when there is a problem, everyone starts the blame game. Nothing unusual about that, part of an administrators job is to troubleshoot and prove where the problem starts. When dealing with external databases, there can be numerous problem, the firewall could be […]
read moreOCI on RHEL6
- Mar
- 31
- Posted by TKH Specialist
- Posted in redhat
Our developers had to have OCI. Now that I got that out of the way. 😉 We use Oracle as our DB for most applications (calm down, like you couldn’t have figured that out). In setting up a new application server for a custom application it came to my attention that the application used oci […]
read morePain often equals Progress
- Nov
- 07
- Posted by TKH Specialist
- Posted in redhat, System Administration, Tools
It has been one of those weeks. Not fun, to many hours worked, personal events missed, you know the kind of week I am talking about. If not…what do you do for a living?! Despite all the pain and stress this week has resulted in Progress, an increased understanding of certain products and new ways […]
read moreSSH – weak ciphers and mac algorithms
- Jun
- 25
- Posted by TKH Specialist
- Posted in System Administration, Tools
A security scan turned up two SSH vulnerabilities: SSH Server CBC Mode Ciphers Enabled SSH Weak MAC Algorithms Enabled To correct this problem I changed the /etc/sshd_config file to: # default is aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128, # aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc, # aes256-cbc,arcfour # you can removed the cbc ciphers by adding the line Ciphers aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,arcfour # default is hmac-md5,hmac-sha1,hmac-ripemd160,hmac-sha1-96,hmac-md5-96 # […]
read moreRemember when you issued that command…?
- Jan
- 06
- Posted by TKH Specialist
- Posted in System Administration
- 2
Bash History: Display Date And Time For Each Command When working in a clustered environment where sometimes documentation gets written past, it is often helpful to know when you issued certain commands. The bash history is great except it doesn’t include a date/time stamp by default. Here is how to add one: To display the […]
read moreYum that was useful!
- Aug
- 09
- Posted by TKH Specialist
- Posted in redhat
Pardon the humor. Just a collection of useful yum commands that are useful to have around but I don’t always remember off the top of my head. I’ll be adding to this post over time. How to list the files installed by a yum package You will need ‘repoquery‘ which is part of ‘yum-utils‘. If […]
read moreFlush This!
- Aug
- 06
- Posted by TKH Specialist
- Posted in redhat, System Administration
- 1
I came across this today and learned something new so thought I would share it here. After killing 2 processes that had hung I noticed the following in the ps output: root 373 2 0 Jun11 ? 00:00:00 [kdmflush] root 375 2 0 Jun11 ? 00:00:00 [kdmflush] root 863 2 0 Jun11 ? 00:00:00 [kdmflush] […]
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