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
$102.22
Apple Inc.
+1.16
MSFT
$46.89
Microsoft Corpora
-0.18
GOOG
$582.60
Google Inc.
-4.78

MacTech Search:
Community Search:

Software Updates via MacUpdate

GarageSale 6.8 - Create outstanding eBay...
GarageSale is a slick, full-featured client application for the eBay online auction system. Create and manage your auctions with ease. With GarageSale, you can create, edit, track, and manage... Read more
ScreenFlow 4.5.3 - Create screen recordi...
Save 5% with the MacUpdate coupon code: 68031AE15F -- Buy now! ScreenFlow is powerful, easy-to-use screencasting software for the Mac. With ScreenFlow you can record the contents of your entire... Read more
NeoOffice 2014.3 - Mac-tailored, OpenOff...
NeoOffice is a complete office suite for OS X. With NeoOffice, users can view, edit, and save OpenOffice documents, PDF files, and most Microsoft Word, Excel, and PowerPoint documents. NeoOffice 3.x... Read more
Typinator 6.2 - Speedy and reliable text...
Typinator turbo-charges your typing productivity. Type a little. Typinator does the rest. We've all faced projects that require repetitive typing tasks. With Typinator, you can store commonly used... Read more
PopChar X 6.7 - Floating window shows av...
PopChar X helps you get the most out of your font collection. With its crystal-clear interface, PopChar X provides a frustration-free way to access any font's special characters. Expanded... Read more
Evernote 5.6.0 - Create searchable notes...
Evernote allows you to easily capture information in any environment using whatever device or platform you find most convenient, and makes this information accessible and searchable at anytime, from... Read more
Monosnap 2.2.2 - Versatile screenshot ut...
Monosnap allows you to save screenshots easily, conveniently, and quickly, sharing them with friends and colleagues at once. It's the ideal choice for anyone who is looking for a smart and fast... Read more
Tunnelblick 3.4beta36 - GUI for OpenVPN...
Tunnelblick is a free, open source graphic user interface for OpenVPN on OS X. It provides easy control of OpenVPN client and/or server connections. It comes as a ready-to-use application with all... Read more
SoftRAID 5.0.4 - High-quality RAID manag...
SoftRAID allows you to create and manage disk arrays to increase performance and reliability. SoftRAID's intuitive interface and powerful feature set makes this utility a must have for any Mac OS X... Read more
Audio Hijack Pro 2.11.3 - Record and enh...
Audio Hijack Pro drastically changes the way you use audio on your computer, giving you the freedom to listen to audio when you want and how you want. Record and enhance any audio with Audio Hijack... Read more

Latest Forum Discussions

See All

PlayHaus Review
PlayHaus Review By Amy Solomon on September 23rd, 2014 Our Rating: iPad Only App - Designed for the iPad PlayHaus is a interesting, stylish app for young children, full of cause-and-effect interactions.   | Read more »
Astropolo Review
Astropolo Review By Amy Solomon on September 23rd, 2014 Our Rating: Universal App - Designed for iPhone and iPad Astropolo is a space-themed children’s app with a great sense of style.   | Read more »
New E*TRADE Update Includes Touch ID and...
New E*TRADE Update Includes Touch ID and Home Screen Widget for iOS 8 Posted by Jessica Fisher on September 23rd, 2014 [ permalink ] | Read more »
Cupcake Carnival Review
Cupcake Carnival Review By Jennifer Allen on September 23rd, 2014 Our Rating: :: SAME OLDUniversal App - Designed for iPhone and iPad Cupcake Carnival does all the right match-3 things but it’s a format we’ve seen a little too... | Read more »
This Week at 148Apps: September 15-19, 2...
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 »
Kitty Powers’ Matchmaker – Tips, Tricks,...
Hey There, Kittens: | Read more »
Goblin Sword Review
Goblin Sword Review By Andrew Fisher on September 22nd, 2014 Our Rating: :: RETRO GOODNESSUniversal App - Designed for iPhone and iPad Fun visuals, good music, engaging level design, and lots of content make Goblin Sword an... | Read more »
Major New Update for CSR Racing Adds Fer...
Major New Update for CSR Racing Adds Ferrari and Multiplaye​r Posted by Jessica Fisher on September 22nd, 2014 [ permalink ] | Read more »
Veditor Review
Veditor Review By Jennifer Allen on September 22nd, 2014 Our Rating: :: PIMP YOUR VIDEOUniversal App - Designed for iPhone and iPad Want to add stickers and music to your videos? Veditor can do that easily.   | Read more »
1849′s Nevada Silver DLC is Still Search...
A few months ago, I took a look at 1849 from SomaSim. This Gold Rush-themed city builder for iPad had a fair bit going for it, but lacked in a few crucial areas to make it a true stand-out on the App Store. SomaSim has since added in a sandbox mode... | Read more »

Price Scanner via MacPrices.net

Check Apple prices on your device with iTracx
MacPrices is proud to offer readers a free iOS app (iPhones, iPads, & iPod touch) and Android app (Google Play and Amazon App Store) called iTracx, which allows you to glance at today’s lowest... 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
New iPhones Score Big in SquareTrade Breakabi...
SquareTrade has announced the iPhone 6 and its larger sibling, iPhone 6 Plus, performed impressively in Breakability testing, and each carries the top Breakability Score in their respective category... Read more
10 Million + First Weekend Sales Set New iPho...
Apple has announced it sold over 10 million new iPhone 6 and iPhone 6 Plus models, a new record, just three days after the launch on September 19. iPhone 6 and iPhone 6 Plus are now available in the... Read more
Betty Crocker Launches New Cookbook for iOS
Betty Crocker, a General Mills brand, an established food industry leader, has announced its free digital cookbook app has been refreshed to make cooking with iPhone, iPad and iPod touch even easier... Read more
Apple restocks some refurbished 2014 MacBook...
The Apple Store has restocked some Apple Certified Refurbished 2014 MacBook Airs, with prices starting at $769. An Apple one-year warranty is included with each MacBook, and shipping is free. These... Read more
13-inch 128GB MacBook Air on sale for $949, s...
B&H Photo has the new 2014 13″ 1.4GHz/128GB MacBook Air on sale for $949.99 including free shipping plus NY tax only. Their price is $50 off MSRP. B&H will also include free copies of... Read more
Apple offering free $25 iTunes Gift Card with...
The Apple Store is offering a free $25 iTunes Gift Card with the purchase of a $99 Apple TV for a limited time. Shipping is free. Read more
Apple refurbished iPod touch available for up...
The Apple Store has Apple Certified Refurbished 5th generation iPod touches available starting at $149. Apple’s one-year warranty is included with each model, and shipping is free. Most colors are... Read more
iFixIt Tears Down iPhone 6; Awards Respectabl...
iFixit notes that even the smaller 4.7″ iPhone 6 is a giant among iPhones; so big that Apple couldn’t fit it into the familiar iPhone form factor. In a welcome reversal of a recent trend to more or... Read more

Jobs Board

*Apple* Solutions Consultant (ASC) - Apple (...
**Job Summary** The ASC is an Apple employee who serves as an Apple brand ambassador and influencer in a Reseller's store. The ASC's role is to grow Apple Read more
Project Manager / Business Analyst, WW *Appl...
…a senior project manager / business analyst to work within our Worldwide Apple Fulfillment Operations and the Business Process Re-engineering team. This role will work Read more
*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
*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.