Category Archives: Unix

Mac OS X Ubuntu Unix

Bash: A Silly wc Example

The wc command is used to count words, characters and lines. Here, we’ll run it a few different ways. -l shows the number of lines in a file. For example, in my home directory, I can use it to see how many lines are in my .gitconfig file:

wc -l .gitconfig

This would output something like the following:

11 .gitconfig

Or count the number of characters with -c:

wc -c .gitconfig

Or check the number of words:

wc -w .gitconfig

You can also run it against multiple files. For example, here I’ll check the number of lines in both my .gitconfig file and my .gitignore_global files:

wc -l .gitconfig .gitignore_global

Let’s say I have a list of numbers and I want to take an average of them. I can use this to quickly figure out how many numbers I have (and so will divide by) before tallying them up.

Mac OS X Mac Security Ubuntu Unix

Remove All Files Except jamf.log From A Directory

You can redirect a log file into a given directory. That directory, if it has other stuff in it, can get out of control. So, here, we’re going to remove all files except that file using the find command:

find * ! -name jamf.log -type f -delete

Once run, the jamf.log is the last file left in the directory.

Mac OS X Ubuntu Unix WordPress

Resolve InnoDB Errors In MySQL

Database won’t start? InnoDB errors are a pain. Where was krypted for a month? Did everything finally get to me and I gave up blogging? No, the site ended up having some problems with corruption in some rows of the InnoDB tables. But, I was able to get the site back up by putting the database into recovery mode. How did I do this? It’s pretty straight forward. Open my.cnf and paste these lines in there:

innodb_force_recovery=3
innodb_purge_threads=0

Once the corruption is resolved, bring up empty databases and import your mysqldump into the new databases and link your site back up. But, the InnoDB force recovery puts the database into recovery mode, which is read only. So I wasn’t actually able to use the site, just look at it. At least the content was available, right? When MySQL isn’t writeable, you can’t log in as an admin, etc. The rest is one of the bigger pains I’ve encountered that didn’t result in an all nighter at a customer. I’ll write that up when I have time some day. In the meantime, next time someone changes my root password and breaks my backup scripts so I can’t just bring in a mysqldump, I’m breaking their arms. You’ve been warned.

Mac OS X Programming Unix

Mac DevOps Conference

There’s another new conference in town! Well, not my town, but Vancouver. MacDev Ops is a hot topic. One that will only increase in the coming years. Thanks to Mat X and Brian Warsing for bringing about a brilliant conference.

Screen Shot 2015-03-23 at 10.43.50 PM

The conference will be held on June 19, 2015 and is an easy $99 if you sign up soon. Also, submit a talk if DevOps is your thing. They’re looking to bring the following topics to the table:

  • Puppet, Chef and other automation from Desktop to Cloud and back
  • Software deployment with Munki and AutoPkg: the app ecosystem surrounding it
  • Cool tools: demo of awesome Mac Admin projects from GitHub
  • DevOps: How to adopt Automation and Best practices in IT operations
  • Dev skills: workshops on Ruby, Git, Python, Javascript for Mac Admins
  • MDM: Profiles and Mac configuration management in the cloud

This is sure to be a good one. Check it out here!

Ubuntu Unix

See Version Information In Linux

There are a number of ways to see information about what version of Linux that you’re running on different

cat /etc/lsb-release

Which returns the distribution information, parsed as follows:

DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=12.04.5
DISTRIB_CODENAME=precise
DISTRIB_DESCRIPTION="Ubuntu Precise Pangolin (LTS)"

LSB_release can also be run as a command, as follows:

lsb_release -a

Which returns the following:

No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu Precise Pangolin (LTS)
Release: 12.04.5
Codename: precise

lab_release can be used as a command as well:

cat /etc/issue.net

Which returns:

Ubuntu Precise Pangolin
(development branch)

In Debian, you can simply look at the version file:

cat /etc/debian_version

Which returns the following:

wheezy/sid

Or Red Hat Enterprise can also be located with /etc/issue.net:

cat /etc/issue.net

With many variants, including OS X, you can also use uname to determine kernel extensions, etc:

uname -a

The thing I’ve learned about Linux is that there’s always a better way to do things. So feel free to comment on your better way or favorite variant!

Mac OS X Mac OS X Server Mac Security Mass Deployment Ubuntu Unix WordPress

Install Pow for Rails Testing On OS X

Pow is a Rack server for OS X. It’s quick and easy to use and lets you skip that whole update an Apache file, then edit /etc/hosts, ethane move a file, then run an app type of process. To get started with Pow, curl it down and pipe it to a shell, then provide the password when prompted to do so:

odr:~ charlesedge$ curl get.pow.cx | sh
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 9039 100 9039 0 0 10995 0 --:--:-- --:--:-- --:--:-- 10996
*** Installing Pow 0.5.0...
*** Installing local configuration files...
/Users/charlesedge/Library/LaunchAgents/cx.pow.powd.plist
*** Installing system configuration files as root...
Password:
/Library/LaunchDaemons/cx.pow.firewall.plist
/etc/resolver/dev
*** Starting the Pow server...
*** Performing self-test...
*** Installed

For troubleshooting instructions, please see the Pow wiki:
https://github.com/basecamp/pow/wiki/Troubleshooting

To uninstall Pow, `curl get.pow.cx/uninstall.sh | sh`

To install an app into Pow, create a symlink to it using ln (assuming ~/.pow is your current working directory):

ln -s /path/to/myapp

Then just open the url, assuming my app is kryptedapp.com:

open http://kryptedapp.com

Pow can also use ~/Library/LaunchAgents/cx.pow.powd.plist to port proxy. This allows you to redirect different apps to different ports. When pow boots, it runs .powconfig, so there’s a lot you can do there, like export, etc. Once you’re done testing out pow, if you don’t decide it’s awesome, remove it with the following command:

curl get.pow.cx/uninstall.sh | sh

Ubuntu Unix

Linux and Free Memory Space

The free command in Linux is used to show memory utilization. When run without any options, you can see the used and available space of swap and physical memory. By default, the option is displayed in kilobytes but when run with a -b option it is shown in bytes or -m will show in megabytes or -g in gigabytes or -t in terabytes. So to see the free space in bytes run the following:

free -b

The -o option shows the output adjusted for the buffer. The -t option also adds a total column as well as a line for total that shows swap and physical, combined. The -s will update the output and is followed by a number of seconds. To see the number of times it happened, use the -c option. So to see the output every 60 seconds:

free -cs 60

The low and high stats are shown using the -l option:

free -l

As with many commands, you can see the version of the command using the -V option:

free -V

Finally, use the –help option to see the available options, no matter the version or OS.

Mac OS X Mac OS X Server Mac Security Mass Deployment Network Infrastructure Programming Ubuntu Unix

Opposite Day: Reversing Lines In Files

The other day, my daughter said “it’s opposite day” when it was time to do a little homework, trying to get out of it! Which reminded me of a funny little command line tool called rev. Rev reads a file and reverses all the lines. So let’s touch a file called rev ~/Desktop/revtest and then populate it with the following lines:

123
321
123

Now run rev followed by the file name:

rev ~/Desktop/revtest

Now cat it:

cat !$

Now rev it again:

rev !$

You go go forward and back at will for fun, much more fun than homework… Enjoy!

Mac OS X Mac OS X Server Mac Security Mass Deployment Network Infrastructure sites Ubuntu Unix

Manage Apex Domains In OS X

OS X Server supports running a traditional bind implementation of DNS. You can define a record for most any name, including google.com, www.google.com, www.www.google.com, etc. You can use this to redirect subdomains. In this example, we’ll create an A Record to point www.google.com to 127.0.0.1 without breaking other google.com subdomains. To get started, let’s use the DNS service in the Server app to create test.www.google.com. The reason for this is that OS X will then create a zone file for www.google.com. If we created www.google.com instead, then OS X would automatically create google.com, which would break the other subdomains. To do so, open Server app and click on the DNS Service. Then click on the plus sign to create a new record.

Screen Shot 2014-09-23 at 10.55.58 AM

Now, if you restart dns and ping test.www.google.com you should see the referenced IP. To then change www.google.com, we’d edit the zone file stored at /Library/Server/named/db.www.krypted.com. This file will look like this when you first open it:

www.google.com. 10800 IN SOA www.google.com. admin.www.google.com. (
2014092301 ; serial
3600 ; refresh (1 hour)
900 ; retry (15 minutes)
1209600 ; expire (2 weeks)
86400 ; minimum (1 day)
)
10800 IN NS test.www.google.com.
test.www.google.com. 10800 IN A 127.0.0.1

We’ll add an a record for a.www.google.com:

a.www.google.com. 10801 IN A 127.0.0.1

Now, to change the apex record, you’d just replace the name you’ve been using with an @:

@ 10801 IN A 127.0.0.1

Good luck!