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 .

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Apple iTunes 12.6.2 - Play Apple Music a...
Apple iTunes lets you organize and stream Apple Music, download and watch video and listen to Podcasts. It can automatically download new music, app, and book purchases across all your devices and... Read more
Transmit 5.0 - Excellent FTP/SFTP client...
Transmit is an excellent FTP (file transfer protocol), SFTP, S3 (Amazon.com file hosting) and iDisk/WebDAV client that allows you to upload, download, and delete files over the internet. With the... Read more
Adobe Lightroom 6.12 - Import, develop,...
Adobe Lightroom is available as part of Adobe Creative Cloud for as little as $9.99/month bundled with Photoshop CC as part of the photography package. Lightroom 6 is also available for purchase as a... Read more
Google Earth 7.3.0.3830 - View and contr...
Google Earth gives you a wealth of imagery and geographic information. Explore destinations like Maui and Paris, or browse content from Wikipedia, National Geographic, and more. Google Earth combines... Read more
Cocktail 10.4.1 - General maintenance an...
Cocktail is a general purpose utility for macOS that lets you clean, repair and optimize your Mac. It is a powerful digital toolset that helps hundreds of thousands of Mac users around the world get... Read more
iMazing 2.3.2 - Complete iOS device mana...
iMazing (was DiskAid) is the ultimate iOS device manager with capabilities far beyond what iTunes offers. With iMazing and your iOS device (iPhone, iPad, or iPod), you can: Copy music to and from... Read more
Backup and Sync 3.35.5978.2967 - File ba...
Backup and Sync (was Google Drive) is a place where you can create, share, collaborate, and keep all of your stuff. Whether you're working with a friend on a joint research project, planning a... Read more
Google Earth 7.3.0.3830 - View and contr...
Google Earth gives you a wealth of imagery and geographic information. Explore destinations like Maui and Paris, or browse content from Wikipedia, National Geographic, and more. Google Earth combines... Read more
Transmit 5.0 - Excellent FTP/SFTP client...
Transmit is an excellent FTP (file transfer protocol), SFTP, S3 (Amazon.com file hosting) and iDisk/WebDAV client that allows you to upload, download, and delete files over the internet. With the... Read more
iMazing 2.3.2 - Complete iOS device mana...
iMazing (was DiskAid) is the ultimate iOS device manager with capabilities far beyond what iTunes offers. With iMazing and your iOS device (iPhone, iPad, or iPod), you can: Copy music to and from... Read more

Latest Forum Discussions

See All

The best deals on the App Store this wee...
There are quite a few truly superb games on sale on the App Store this week. If you haven't played some of these, many of which are true classics, now's the time to jump on the bandwagon. Here are the deals you need to know about. [Read more] | Read more »
Realpolitiks Mobile (Games)
Realpolitiks Mobile 1.0 Device: iOS Universal Category: Games Price: $5.99, Version: 1.0 (iTunes) Description: PLEASE NOTE: The game might not work properly on discontinued 1GB of RAM devices (iPhone 5s, iPhone 6, iPhone 6 Plus, iPad... | Read more »
Layton’s Mystery Journey (Games)
Layton’s Mystery Journey 1.0.0 Device: iOS Universal Category: Games Price: $15.99, Version: 1.0.0 (iTunes) Description: THE MUCH-LOVED LAYTON SERIES IS BACK WITH A 10TH ANNIVERSARY INSTALLMENT! Developed by LEVEL-5, LAYTON’S... | Read more »
Full Throttle Remastered (Games)
Full Throttle Remastered 1.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0 (iTunes) Description: Originally released by LucasArts in 1995, Full Throttle is a classic graphic adventure game from industry legend Tim... | Read more »
Stunning shooter Morphite gets a new tra...
Morphite is officially landing on iOS in September. The game looks like the space shooter we've been needing on mobile, and we're going to see if it fits the bill quite shortly. The game's a collaborative effort between Blowfish Studios, We're Five... | Read more »
Layton's Mystery Journey arrives to...
As you might recall, Layton's Mystery Journey is headed to iOS and Android -- tomorrow! To celebrate the impending launch, Level-5's released a new trailer, complete with an adorable hamster. [Read more] | Read more »
Sidewords (Games)
Sidewords 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: Grab a cup of coffee and relax with Sidewords. Sidewords is part logic puzzle, part word game, all original. No timers. No... | Read more »
Noodlecake Games' 'Leap On!...
Noodlecake Games is always good for some light-hearted arcade fun, and its latest project, Leap On! could carry on that tradition. It's a bit like high stakes tetherball in a way. Your job is to guide a cute little blob around a series of floating... | Read more »
RuneScape goes mobile later this year
Yes, RuneScape still exists. In fact, it's coming to iOS and Android in just a few short months. Jagex, creators of the hit fantasy MMORPG of yesteryear, is releasing RuneScape Mobile and Old School RuneScape for mobile devices, complete with... | Read more »
Crash of Cars wants you to capture the c...
Crash of Cars is going full on medieval in its latest update, introducing castles and all manner of new cars and skins fresh from the Dark Ages. The update introduces a new castle-themed map (complete with catapults) and a gladiator-style battle... | Read more »

Price Scanner via MacPrices.net

DEVONthink To Go 2.1.7 For iOS Brings Usabili...
DEVONtechnologies has updated DEVONthink To Go, the iOS companion to DEVONthink for Mac, with enhancements and bug fixes. Version 2.1.7 adds an option to clear the Global Inbox and makes the grid... Read more
15-inch 2.2GHz Retina MacBook Pro, Apple refu...
Apple has Certified Refurbished 2015 15″ 2.2GHz Retina MacBook Pros available for $1699. That’s $300 off MSRP, and it’s the lowest price available for a 15″ MacBook Pro. An Apple one-year warranty is... Read more
13-inch 2.3GHz Silver MacBook Pro on sale for...
B&H Photo has the new 2017 13″ 2.3GHz/256GB Silver MacBook Pro (MPXU2LL/A) on sale for $1399 including free shipping plus NY & NJ sales tax only. Their price is $100 off MSRP. Read more
Apple Tackles Distracted Driving With iOS 11...
One of the most important new features coming in iOS 11 is Do Not Disturb while driving, intended to help drivers stay more focused on the road. With Do Not Disturb while driving, your iPhone can... Read more
iMazing Mini for Mac: Free Automatic and Priv...
Geneva, Switzerland-based indie developer DigiDNA has released iMazing Mini, their free macOS utility designed to automatically back up iOS devices over any local Wi-Fi network. The app offers users... Read more
Clearance 2016 13-inch MacBook Airs, Apple re...
Apple dropped prices recently on Certified Refurbished 2016 13″ MacBook Airs, with models now available starting at $809. An Apple one-year warranty is included with each MacBook, and shipping is... Read more
9.7-inch 2017 iPads available for $299, save...
B&H Photo has 2017 9.7″ 32GB WiFi iPads on sale for $30 off MSRP for a limited time. Shipping is free, and pay sales tax in NY & NJ only: – 32GB iPad WiFi: $299, $30 off Read more
Welcome to the new MacPrices.net!
Welcome to the newly redesigned MacPrices.net! MacPrices has been comprehensively redesigned from the ground up over the past couple of weeks. The new design is cleaner, with less clutter, minimal... Read more
Clearance iMacs available for up to $370 off...
B&H Photo has clearance 21″ and 27″ Apple iMacs available for up to $370 off original MSRP, each including free shipping plus NY & NJ sales tax only: – 27″ 3.3GHz iMac 5K: $1929 $370 off... Read more
Sale! 15-inch 2.8GHz MacBook Pros for $100 of...
B&H Photo has the new 2017 15″ 2.8GHz Touch Bar MacBook Pros on sale for $100 off MSRP. Shipping is free, and B&H charges sales tax in NY & NJ only: – 15″ 2.8GHz MacBook Pro Space Gray: $... Read more

Jobs Board

Manager, *Apple* Media Products - Apple Inc...
Job Summary The Apple Media Products Discovery, Fraud and Abuse team is responsible for protecting the integrity of Apple services. As a manager of the team, you Read more
*Apple* Watch, Accessories, Engineering Proj...
Job Summary Engineering Project Manager, Apple Watch Accessories. The Accessories group is looking for an Engineering Project Manager (EPM) to lead the design and Read more
Sr. Technical Writer - *Apple* Information...
Changing the world is all in a day's work at Apple . If you love innovation, here's your chance to make a career of it. You'll work hard. But the job comes with more Read more
Full Stack Web Developer - *Apple* Maps Tra...
Changing the world is all in a day's work at Apple . If you love innovation, here's your chance to make a career of it. You'll work hard. But the job comes with more Read more
Program Manager, *Apple* Pay - Apple Inc. (...
Job Summary Apple is looking for a dynamic, highly motivated Program Manager to join the Apple Pay business team.As the Apple Pay Program Manager, you'll be Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.