TweetFollow Us on Twitter

Mac In The Shell -- Which Log?

Volume Number: 23 (2007)
Issue Number: 03
Column Tag: Mac in the Shell

Mac In The Shell -- Which Log?

Following up on which log shows you what

by Edward Marczak

Introduction

I've had incredible response to my last two columns that talked about logs: what they are, how to interpret them and how to notify yourself if a log is telling you something important. More than any other question, however, people have asked, "which log does what? While I gave an overview of some logs, there are plenty more that I haven't gone into, and more locations for logs than I could describe previously. That's what I'll be following up on this month. So, read on for even more on logs.

Kinda I Want To

Just as a review for anyone who didn't read the previous columns, logs are text files that running programs write to that keep track of their activity. Text files, that's all. (OK, an app could keep a binary log, but for the most part, text it is). This allows other apps and, more importantly, humans to read their contents. Apps are free to deal with logging on their own, or, they can use syslog to hand off their data to the system logger. It's a bit of a style issue, and usage is roughly split on which method is chosen. There's nothing that says that an application can't do both. Let's look quickly again at the syslog method.

The system logger, aka "syslog, is a daemon run at boot that should be running all of the time. It listens for logging data locally, and knows where to put a logging entry based on its configuration file /etc/syslog.conf. "syslogd can also be setup to listen for logging data from other machines as well. Log data can be categorized by facility and level (a "selector). The facility is basically where the data is coming from ("mail, "ftp, etc., along with some generic facilities). The level describes the severity of the log message. The currently defined levels are:

Emergency (level 0) Alert (level 1) Critical (level 2) Error (level 3) Warning (level 4) Notice (level 5) Info (level 6) Debug (level 7)

(Don't you love it when things neatly fit into a byte?) Looking at /etc/syslog.conf, you can then see which messages will be directed to which files. Note that some will go to multiple files.

This is a bit of a review, as all of this (and more) was covered in previous articles in this column.

Down In It

Apple has created a little bit of a split with logging: "Unix-y files in /var/log, and everything else. While that may be a bit of an overgeneralization, it's a good general guideline.

syslogd, as you can see from /etc/syslog.conf, will dump just about everything in some log residing in /var/log. Additionally, several non-syslog sending services also drop their files somewhere into the /var/log hierarchy. The two big notables in this category would be apache logging into /var/httpd and samba, which logs into /var/samba. You'll also find some other non-syslog-ish files hanging around in /var/log, and we'll address those a little later.

The other place you'll find good logging information falls into the "everything else category. You'll find these in /Library/Logs or ~/Library/Logs. System processes will log to /Library/Logs and user processes, when the user home directory is writable, will log to ~/Library/Logs. For example, anything that needs admin level rights to run AFP logs, Software Update and, my favorite, Directory Services will log to the System directory /Library/Logs. Other user-space apps Logic, SyncServices, Parallels, etc. will log into the user's own Library/Logs.

If you've peeked into either of these directories, you'll notice that there's another category of logs: logs that get generated as the result of a crash.

Something I Can Never Have

For those of you obsessed with the running process list, you'll no doubt have noticed the persistent /usr/libexec/crashreporterd. Apple's crash reporter daemon hangs around waiting for an application to crash. Technically, it listens for a Mach exception to be generated, and, upon that happening, launches crashdump. crashdump then logs and reports the event to the user. If the user can be determined, and they have a writable home, the report goes into ~/Library/Logs/CrashReporter. You really forget how much stuff takes a dive until you peek in there:

Jack-Kerouac:~/Library/Logs/CrashReporter marczak$ ls -1
BOMArchiveHelper.crash.log
Cyberduck.crash.log
Dreamweaver.crash.log
Finder.crash.log
GrowlTunes.crash.log
Mail.crash.log
Now Up-To-Date.crash.log
Pages.crash.log
Parallels.crash.log
Preview.crash.log
Quicksilver.crash.log
Safari.crash.log
VirtueDesktops.crash.log
Workgroup Manager.crash.log
firefox-bin.crash.log
iSnip.crash.log
mdimportserver.crash.log
vmware.crash.log

Wow. When an app's owner can't be determined, is a system process, or the user's home directory is not writeable, crashdump logs into /Library/Logs:

Jack-Kerouac:/Library/Logs/CrashReporter root# ls -1 
ARDAgent.crash.log
Exited process.crash.log
httpd.crash.log
iSnip.crash.log
loginwindow.crash.log

LoginWindow crash...I like that one! crashreporter itself, however, logs its actions into /var/log/crashreporter.log. Finally, crashreporterd is also responsible for writing panic logs when the system is rebooted after a panic find the log at /Library/Logs/panic.log.

Terrible Lie

If you root around /var/log long enough, you'll even start to notice some other files that aren't syslog generated at all. The most notable of the bunch are daily.out, weekly.out and monthly.out. These log files are generated by the daily, weekly and monthly periodic jobs that run overnight (if your machine is up and running, but not necessarily logged in).

Also of note are wtmp and lastlog. Interestingly, these are binary log files, and must be read with another application. These are not present for troubleshooting per se, but instead track login activity. User IDs, along with their login time get written to lastlog. From there, the utmp file gets updated with the user login information, and the same utmp record gets written to /var/log/wtmp. users, w and who use utmp to provide their information, while last and ac use wtmp.

That's What I Get

So, back to the original question: which logs record which bit of information? Here's a 40,000 ft. view:

/var/log/system.log

Along with asl.log, these are the big kahunas. Most system related activity is logged here. Specifically, the following selectors log to system.log:

*.notice
authpriv,remoteauth,ftp,install.none
kern.debug
mail.crit

As mentioned in January, asl.log pretty much gets everything, and displays the facility and level with the log message.

/var/log/secure.log

Messages from Apple's SecurityServer get logged here along with anything in the authpriv facility. Good one to keep an eye on. Interestingly, though, some security-related information logs to system log as well (such as sshd authentication errors through PAM).

/var/log/mail.log and /var/log/mailaccess.log

Complimentary logs that describe mail (if you're running OS X Server's built-in mail OS X client' also uses /var/log/mail.log). mail.log contains activity for postfix, SMTP sending and receiving while mailaccess.log contains cyrus' imap and pop activity. mail.log is the place to look when clients are telling you that they sent mail that the intended recipients never received (mail going out), or that someone sends them e-mail which they themselves never received (mail coming in).

/Library/Logs/DirectoryService/*

Huge. HUGE I say! Anyone operating in an OD, AD or other LDAP-reliant environment should be checking here occasionally. Of course, if you're trying to bind a workstation to a directory, and it's just not working for some reason, this is the place to check. Don't forget to throw DirectoryService into debug mode (killall -USR1 DirectoryService, logging to DirectoryService.debug.log), or use boot-time debugging (touch /Library/Preferences/DirectoryService/.DSLogDebugAtStart which will also log to DirectoryService.debug.log) if the situation calls for it covered in detail in past Mac In The Shell articles.

Logs that you don't need explained

There are some logs that simply don't need any explanation. These include:

/var/log/ftp.log (contents of the ftp server)
/var/log/httpd/* (Apache's log files)
/var/log/samba/* (Samba's log files)
/var/log/lpr.log (lpr printing activity)
/var/log/cups/* (CUPS web sever activity)
/Library/Logs/Software Update.log (Software Update install history)

/Library/Logs/AppleFileService OK, perhaps this one does need some explanation. But not by me from the engineers at Apple. This should be the Mecca of information that you reach for when you want to track activity coming in through AFP. However, details in this log are so sparse to render it useless. Despite the fact that AppleFileServer runs as one grand, monolithic process, we need it to give up the goods on what's happening internally in these logs.

The mega-log

Remember, that you can always have all syslog messages be delivered to a single file by using a wildcard selector in /etc/syslog.conf:

*.*      /var/log/mega.log

…although asl.log is already catching most of that. Further remember that this will not capture everything else that is performing logging on its own and not using syslog/asl.

The Only Time

While I made a strong case for watching and examining logs using good ol Unix tools grep, tail and less and I would still make that assertion, there are some other very useful tools out there.


Figure 1: Splunk searching for events (detail)

Console.app is the most obvious for us Mac users; it's "built-in and clearly Mac-like. I still think it's a miserable way to follow log activity as it happens, but it is a fantastic tool for exploring the various logs that exist on the system. Fire up Console.app (located in the Utilities folder) and poke around. It's a great learning experience.

I've found a newer tool on the market to also be very useful, and while it's not Mac-specific, it's nice that there's an OS X version at all. Splunk is billed as a logfile search engine. It comes in a free version that will sift through up to 500MB of logs per day, and a paid version which not only removes that restriction altogether, but also adds Splunk-to-Splunk logging for log correlation across many machines, and also authentication which is missing in the free version.

Splunk alone could take up an entire column (and may very well one day soon); it is so easy to get going, that I'd recommend the download. Excellent documentation exists on the site as well. Of course, Splunk makes it really easy to search for events, but I've found that it's a nice exploratory tool in general. Splunk quickly categorizes events and can let you filter on those events. Figure 1 shows the search engine, running in a browser, looking at event type 9 on my machine.

Even cooler, perhaps, is the ability to look at the frequency of events. Figure 2 shows the frequency of events that appear in the secure.log of my machine clearly a good one to keep an eye on and reign in this kind of data.


Figure 2 Splunk showing the frequency of various events that appear in a given source.

In a small-to-medium sized organization, you could set up a single server as a log host (check the prior logging articles for instructions) and have Splunk access that log. 500MB is a lot of logging information. Enough that you shouldn't have a problem using the free version of Splunk.

Sanctified

So here's the real story with logs: you can ignore them, sure. Then when a problem crops up, you can just tell your client/employer that this is just the way computers are. There are bugs, there are problems; such is life. If you watch the logs, you'll know there's a problem, and then you'll actually have to do something about it.

Or, you can realize that this is the only way the system can speak to you and more often that not, you're warned well in advance of any catastrophic problems. You can head these off at the pass. You can keep the system providing services without interruption and keep up with real work.

Of course, the unfortunate cases do arise where you need to ascertain what happened after the fact. Did that mail get sent? Did that volume bomb on space and then recover without us really knowing? Was someone trying to brute-force a login through ssh at the same time our web server was under attack? In those cases, knowing which logs to look in and how to read them are your only resource for piecing together information after an event took place.

Media of the month: you might suspect it would be some Nine Inch Nails title, however, I'd have to disappoint: that was only a passing fancy. The real Media of the Month is, "Innumeracy: Mathematical Illiteracy and Its Consequences by John Allen Paulos. A book that I forgot I had until I lent it out. Easy, enjoyable, powerful reading.

WWDC time again! Apple has announced the dates (June 11th through the 15th, if you'd missed it), so, get ready. If you're attending, I hope to see you there in person! Until then, though, I'll see you in print next month...


Ed Marczak owns and operates Radiotope, a technology consultancy that brings enterprise solutions to small and medium-sized businesses. Outside of this piece of the puzzle, he is Executive Editor of MacTech Magazine, a husband and father, and CTO of WheresSpot, among other things. Find the missing tech piece at .

 
AAPL
$99.76
Apple Inc.
+2.09
MSFT
$44.08
Microsoft Corpora
+0.45
GOOG
$520.84
Google Inc.
+9.67

MacTech Search:
Community Search:

Software Updates via MacUpdate

TechTool Pro 7.0.5 - Hard drive and syst...
TechTool Pro is now 7, and this is the most advanced version of the acclaimed Macintosh troubleshooting utility created in its 20-year history. Micromat has redeveloped TechTool Pro 7 to be fully 64... Read more
PDFKey Pro 4.0.2 - Edit and print passwo...
PDFKey Pro can unlock PDF documents protected for printing and copying when you've forgotten your password. It can now also protect your PDF files with a password to prevent unauthorized access and/... Read more
Yasu 2.9.1 - System maintenance app; per...
Yasu was originally created with System Administrators who service large groups of workstations in mind, Yasu (Yet Another System Utility) was made to do a specific group of maintenance tasks... Read more
Hazel 3.3 - Create rules for organizing...
Hazel is your personal housekeeper, organizing and cleaning folders based on rules you define. Hazel can also manage your trash and uninstall your applications. Organize your files using a... Read more
Autopano Giga 3.7 - Stitch multiple imag...
Autopano Giga allows you to stitch 2, 20, or 2,000 images. Version 3.0 integrates impressive new features that will definitely make you adopt Autopano Pro or Autopano Giga: Choose between 9... Read more
MenuMeters 1.8 - CPU, memory, disk, and...
MenuMeters is a set of CPU, memory, disk, and network monitoring tools for Mac OS X. Although there are numerous other programs which do the same thing, none had quite the feature set I was looking... Read more
Coda 2.5 - One-window Web development su...
Coda is a powerful Web editor that puts everything in one place. An editor. Terminal. CSS. Files. With Coda 2, we went beyond expectations. With loads of new, much-requested features, a few... Read more
Arq 4.6.1 - Online backup to Google Driv...
Arq is super-easy online backup for the Mac. Back up to your own Google Drive storage (15GB free storage), your own Amazon Glacier ($.01/GB per month storage) or S3, or any SFTP server. Arq backs up... Read more
Airfoil 4.8.10 - Send audio from any app...
Airfoil allows you to send any audio to AirPort Express units, Apple TVs, and even other Macs and PCs, all in sync! It's your audio - everywhere. With Airfoil you can take audio from any... Read more
Apple iMovie 10.0.6 - Edit personal vide...
With an all-new design, Apple iMovie lets you enjoy your videos like never before. Browse your clips more easily, instantly share your favorite moments, and create beautiful HD movies and Hollywood-... Read more

Latest Forum Discussions

See All

This Week at 148Apps: October 13-17, 201...
Expert App Reviewers   So little time and so very many apps. What’s a poor iPhone/iPad lover to do? Fortunately, 148Apps is here to give you the rundown on the latest and greatest releases. And we even have a tremendous back catalog of reviews; just... | Read more »
Angry Birds Transformers Review
Angry Birds Transformers Review By Jennifer Allen on October 20th, 2014 Our Rating: :: TRANSFORMED BIRDSUniversal App - Designed for iPhone and iPad Transformed in a way you wouldn’t expect, Angry Birds Transformers is a quite... | Read more »
GAMEVIL Announces the Upcoming Launch of...
GAMEVIL Announces the Upcoming Launch of Mark of the Dragon Posted by Jessica Fisher on October 20th, 2014 [ permalink ] Mark of the Dragon, by GAMEVIL, put | Read more »
Interview With the Angry Birds Transform...
Angry Birds Transformers recently transformed and rolled out worldwide. This run-and-gun title is a hit with young Transformers fans, but the ample references to classic Transformers fandom has also earned it a place in the hearts of long-time... | Read more »
Find Free Food on Campus with Ypay
Find Free Food on Campus with Ypay Posted by Jessica Fisher on October 20th, 2014 [ permalink ] iPhone App - Designed for the iPhone, compatible with the iPad | Read more »
Strung Along Review
Strung Along Review By Jordan Minor on October 20th, 2014 Our Rating: :: GOT NO STRINGSUniversal App - Designed for iPhone and iPad A cool gimmick and a great art style keep Strung Along from completely falling apart.   | Read more »
P2P file transferring app Send Anywhere...
File sharing services like Dropbox have security issues. Email attachments can be problematic when it comes to sharing large files. USB dongles don’t fit into your phone. Send Anywhere, a peer-to-peer file transferring application, solves all of... | Read more »
Zero Age Review
Zero Age Review By Jordan Minor on October 20th, 2014 Our Rating: :: MORE THAN ZEROiPad Only App - Designed for the iPad With its mind-bending puzzles and spellbinding visuals, Zero Age has it all.   | Read more »
Hay Ewe Review
Hay Ewe Review By Campbell Bird on October 20th, 2014 Our Rating: :: SAVE YOUR SHEEPLEUniversal App - Designed for iPhone and iPad Pave the way for your flock in this line drawing puzzle game from the creators of Worms.   | Read more »
My Very Hungry Caterpillar (Education)
My Very Hungry Caterpillar 1.0.0 Device: iOS Universal Category: Education Price: $3.99, Version: 1.0.0 (iTunes) Description: Care for your very own Very Hungry Caterpillar! My Very Hungry Caterpillar will captivate you as he crawls... | Read more »

Price Scanner via MacPrices.net

2013 15-inch 2.0GHz Retina MacBook Pro availa...
B&H Photo has leftover previous-generation 15″ 2.0GHz Retina MacBook Pros now available for $1599 including free shipping plus NY sales tax only. Their price is $400 off original MSRP. B&H... Read more
Updated iPad Prices
We’ve updated our iPad Air Price Tracker and our iPad mini Price Tracker with the latest information on prices and availability from Apple and other resellers, including the new iPad Air 2 and the... Read more
Apple Pay Available to Millions of Visa Cardh...
Visa Inc. brings secure, convenient payments to iPad Air 2 and iPad mini 3as well as iPhone 6 and 6 Plus. Starting October 20th, eligible Visa cardholders in the U.S. will be able to use Apple Pay,... Read more
Textkraft Pocket – the missing TextEdit for i...
infovole GmbH has announced the release and immediate availability of Textkraft Pocket 1.0, a professional text editor and note taking app for Apple’s iPhone. In March 2014 rumors were all about... Read more
C Spire to offer iPad Air 2 and iPad mini 3,...
C Spire on Friday announced that it will offer iPad Air 2 and iPad mini 3, both with Wi-Fi + Cellular, on its 4G+ LTE network in the coming weeks. C Spire will offer the new iPads with a range of... Read more
Belkin Announces Full Line of Keyboards and C...
Belkin International has unveiled a new lineup of keyboard cases and accessories for Apple’s newest iPads, featuring three QODE keyboards and a collection of thin, lightweight folios for both the... Read more
Verizon offers new iPad Air 2 preorders for $...
Verizon Wireless is accepting preorders for the new iPad Air 2, cellular models, for $100 off MSRP with a 2-year service agreement: - 16GB iPad Air 2 WiFi + Cellular: $529.99 - 64GB iPad Air 2 WiFi... Read more
Price drops on refurbished Mac minis, now ava...
The Apple Store has dropped prices on Apple Certified Refurbished previous-generation Mac minis, with models now available starting at $419. Apple’s one-year warranty is included with each mini, and... Read more
Apple refurbished 2014 MacBook Airs available...
The Apple Store has Apple Certified Refurbished 2014 MacBook Airs available for up to $180 off the cost of new models. An Apple one-year warranty is included with each MacBook, and shipping is free.... Read more
Refurbished 2013 MacBook Pros available for u...
The Apple Store has Apple Certified Refurbished 13″ and 15″ MacBook Pros available starting at $929. Apple’s one-year warranty is standard, and shipping is free: - 13″ 2.5GHz MacBook Pros (4GB RAM/... Read more

Jobs Board

*Apple* Retail - Multiple Positions (US) - A...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
Position Opening at *Apple* - Apple (United...
…customers purchase our products, you're the one who helps them get more out of their new Apple technology. Your day in the Apple Store is filled with a range of Read more
Position Opening at *Apple* - Apple (United...
**Job Summary** At the Apple Store, you connect business professionals and entrepreneurs with the tools they need in order to put Apple solutions to work in their Read more
Position Opening at *Apple* - Apple (United...
**Job Summary** The Apple Store is a retail environment like no other - uniquely focused on delivering amazing customer experiences. As an Expert, you introduce people Read more
Position Opening at *Apple* - Apple (United...
**Job Summary** As businesses discover the power of Apple computers and mobile devices, it's your job - as a Solutions Engineer - to show them how to introduce these Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.