wiki:SETroubleShoot User FAQ
Last modified 6 years ago Last modified on 01/21/08 05:32:29

Setroubleshoot User FAQ


  1. What is the basic structure of the alert browser?
  2. How am I alerted when an AVC denial occurs?
  3. Can setroubleshoot send me an email when an alert fires?
  4. What information is displayed in the status bar?
  5. How do I export alert information (clipboard, file, print)?
    1. Copying to the clipboard does not work as I expect
  6. How can I sort the alert list?
  7. What date is associated with an alert?
  8. I think SELinux is the cause of a problem, how can setroubleshoot help find it?
  9. I've got a log file with AVC messages in it, can setroubleshoot analyze it for me?
    1. How can I correlate alerts with the log file line numbers ?
    2. The /var/log/messages log file lists an AVC denial, can setroubleshoot give me more information?
  10. Alerts are not showing up, what's wrong?
  11. How is sealert started?
  12. How do I display the alert browser?
  13. Does sealert run continuously?
  14. How can I stop sealert?
  15. Some alerts are meaningful to me, others are just an annoyance, can I filter them somehow?
  16. Does setroubleshoot have a log I can check?
  17. Does setroubleshoot have a config file?
  18. How do I switch which alerts I'm viewing?
  19. What is an alert?
    1. What is an AVC message?
    2. What is a Denial Event?
  20. What is environment information and why is it sometimes missing?
  21. What is an alert database?
  22. What is an alert signatures?
  23. What is an analysis report?
  24. Can I delete alerts?
  25. Can I hide alerts marked for deletion?
  26. Are there shortcuts for common operations in the browser?


What is the basic structure of the alert browser?

The alert browser is allows you to view and operate on alerts stored in an alert database. The browser is modeled after an email client where each alert corresponds to an email message.

The browser window is composed of 3 components:

source:doc/setroubleshoot_browser_structure.png

The alert list shows you a list of all the alerts and is divided into columns:

Filter::

Toggle a flag to prevent being notified when this alert repeats.

Date::

The date and time of the most recent occurrence of this denial event

Count::

How many times has this denial event been triggered since it was first reported.

Category::

The category (class) this denial event belongs to (e.g.: "Web Server", "FTP", "File System", "Cron", etc.)

Summary::

A brief description of the denial event

All the columns in the alert list can be sorted.

How am I alerted when an AVC denial occurs?

  • You can receive alerts on your desktop

If you are in a desktop session and sealert is running (the default) you will be notified when the setroubleshoot daemon sends a message to sealert. sealert first checks if the alert is being [#alert-filtering filtered], if so sealert remains passively quiet in the background. If the alert is not filtered then sealert puts the setroubleshoot icon source:gui/setroubleshoot_icon.png up in the status area. It then briefly displays a notification balloon indicating an AVC denial has occurred and directs the user to click on the setroubleshoot icon to view it. The notification will time out after a few seconds so it it not obstructively annoying.

Note: The status icon is only displayed if sealert is running when the alert arrives, past unviewed alerts from previous sessions do not cause the status icon to be displayed, instead you can display the browser to view them. This is an example of what a notification looks like:

source:doc/setroubleshoot_notification.png

You may also have setroubleshoot send you an email alert.

Can setroubleshoot send me an email when an alert fires?

Besides desktop notifications setroubleshoot can also send you an alert as an email message. This might be preferable when there is [#no-desktop no desktop], when you want to archive alerts, automatically post-process alerts, or monitor remote systems.

There are two ways to configure email alerts:

  1. Use the alert browser GUI
  1. Manually edit the mailing list

The easiest way to configure email alert is to [#display-browser display the browser] and then from the File menu select "Edit Email Alert List ...". A dialog will pop up:

source:doc/setroubleshoot_email_preferences.png

With the dialog you can:

  • add an address by entering it in the input box and clicking add
  • delete one or more addresses by selecting them in the list and clicking delete or hitting the delete button.
  • edit an address already in the list by clicking on it and typing.
  • modify the filtering for an address by clicking on the filter and

selecting one of the options from the drop down list.

The filter option for email alerts apply to all alerts, unlike in the alert browser you cannot have a different filter for each alert. Here are the filtering options for email alerts:

Ignore After First Alert::

This is the default. The address will receive an alert only the first time it fires. Email alerts will be filtered for the alert in question for all subsequent firings of the alert.

Never Ignore::

An email alert will be sent for every instance of every alert to this address.

Ignore Always::

Email alerts will never be sent for this address. One can use this to temporarily disable alerts to an address.

But I don't have a desktop session on the node I want to receive email alerts for? For instance how can I monitor a server?

You can directly edit the file /var/lib/setroubleshoot/email_alert_recipients. This is the file the above GUI is modifying. The format of the file is line based, the hash (#) character is the comment character, the comment extends to the end of the line, blank lines are ignored.

Addresses are one per line, optionally following the address (seperated by whitespace) are options in the form name=value. Currently there is only one option:

filter_type::

after_first never always

Here is an example:

jdennis@redhat.com                       filter_type=after_first

What information is displayed in the status bar?

At the bottom of the sealert browser window is a status bar. The status bar is divided into 4 areas:

connection status::

This displays the status of the connection to the setroubleshootd daemon. If you are not currently connected sealert will periodically attempt to reconnect displaying messages to that effect in the message area.

visit database::

This is the alert database the browser is currently visiting (e.g. viewing). The default is the 'Audit Listener', which is the database of alerts received from the audit subsystem and managed by the setroubleshootd daemon. If you scan a log file the browser will switch to visiting the database created from the log file scan. You can switch which database is being viewed via the View menu.

message area:

This is where temporary messages of minor importance are displayed.

progress bar::

During time consuming operations such as reading in new data or scanning log files the progress bar will either indicate an estimated percentage of completion or if an estimate is not possible that an operation is underway.

source:/doc/setroubleshoot_statusbar.png

How do I export alert information (clipboard, file, print)?

You can export selected alerts by:

  • copying the alert to the clipboard (Edit|Copy Alert)
  • writing the alert to a file (File|Save As...)
  • printing the alert (File|Print...)

Copying to the clipboard does not work as I expect

There are two ways to copy to the clipboard:

Copy::

This copies the selected items in the alert view to the clipboard. The alert view is rendered as HTML (e.g. a web page). The HTML renderer is asked to perform the copy operation. The current HTML renderer is not very smart about translating table and other HTML elements into text on the clipboard. You get what the HTML renderer is capable of producing. Future releases of setroubleshoot may upgrade to a more capable HTML renderer.

Copy Alert::

The copies the entire alert as TEXT and places it on the clipboard. The text is formatted to resemble the HTML version. When sharing an alert with someone else or pasting it into another application "Copy Alert" will probably provide the best text because it preserves formatting such as line breaks. Although because it includes everything you may have to delete some text you consider superfluous.

How can I sort the alert list?

Each column heading in the alert list is sortable. Just click on the column heading to change the sort order.

What date is associated with an alert?

Alerts store two seperate dates in their description. The date/time the alert was first seen and the date/time the alert was last seen (most recent occurance). The date/time column in the browser shows date/time of the most recent occurance (last seen). The alert detail view shows both date/time's.

I think SELinux is the cause of a problem, how can setroubleshoot help find it?

In this instance you probably know or suspect the problem occurred at a certain time or in a certain component.

If you think the problem is related to a certain component, for instance your web server, then display the browser and sort the Category column. This will group alerts by Category, look for any alerts in the "Web Server" category.

If you think the problem occurred in at a certain time then sort the Date column. Find the alerts which occurred within the time period the problem manifested itself.

I've got a log file with AVC messages in it, can setroubleshoot analyze it for me?

Yes. By default setroubleshoot listens for AVC messages arriving from the audit subsystem and then feeds those AVC messages into its analysis engine. However setroubleshoot can also open a log file containing AVC messages, parse those AVC messages and feed them into its analysis engine just as if they had arrived from the audit subsystem. To analyze a log file go to the File menu and select "Scan logfile...". This will open a file chooser dialog which will allow you to pick a file to analyze.

The file is opened by the sealert process which runs with your permissions, not root permissions. Therefore any file you wish to analyze must be readable by you. Some system log file are not world readable. If this is the case then your best option is to copy the file as root to a temporary location and make it readable.

As the analysis engine runs on the log file it builds an alert database (e.g. post processed). The most significant effect is to collapse recurring problems into single alerts with a repeat count (see alert description).

The browser will switch to viewing (visiting) the alert database created by scanning the log file. The fact the browser is now viewing a different set of alerts is reported in the [#sealert-statusbar status bar]. You may switch which set of alerts you're viewing with the View menu.

The alerts generated from log file scanning do not contain any environmental information (e.g. version information etc.), see alert environment for an explanation of why.

How can I correlate alerts with the log file line numbers ?

Each alert in the detail section will display the line numbers which contributed to the alert. Recall that alerts are single descriptions of a denial which may have occurred multiple times in the log file, the line numbers will show you all the places in the log file where this same issue was identified. In addition denial events are composed from multiple [#avc-message AVC messages] which may or may not be contiguous in the log file (typically denial events have their independent AVC messages in close proximity, thus any given denial event tends to be "clustered"). The line numbers reported are for every AVC message which contributed to a denial event and each alert may be composed from multiple denial evants (e.g. the report count).

The /var/log/messages log file lists an AVC denial, can setroubleshoot give me more information?

Sometimes. As a helpful service when setroubleshootd is running and catches an AVC denial it will write the AVC message into the system log file along with the alert identitifer (e.g. local-id). You can run sealert from the command line with the -l (e.g. lookup) option passing the ID reported in the log file. sealert will then print the alert matching that ID to stdout.

Alerts are not showing up, what's wrong?

I know I'm getting AVC denials but I'm not getting alerts on my desktop. What might be going wrong and how can I fix it?

Setroubleshoot is composed of independent parts, a daemon which runs as a system service with root privileges (setroubleshootd) and a user GUI tool typically run on the desktop (sealert) which communicates with the setroubleshootd daemon. Both setroubleshootd and sealert must be running to receive alerts on your desktop.

  1. Verify the setroubleshootd daemon is running. The connection icon

in the status bar is a quick way to check the sealert is connected to the setroubleshootd daemon.

Otherwise to perform a more thorough, setroubleshootd is installed as a system service called setroubleshoot (no trailing 'd' in the name). Use the 'service' command to check its status like this:

% service setroubleshoot status

You should get one of two messages:

setroubleshootd is stopped

-OR-

setroubleshootd (pid 12345) is running...

If it's running, this part is good, otherwise start the service:

% service setroubleshoot start

If you want to make sure the setroubleshoot service is always running, even after a reboot you'll want to enable the service with the chkconfig command, you would do it like this:

chkconfig setroubleshoot on
  1. Verify the sealert user process is running
% ps ax | grep sealert

This should show a running sealert process. If it's not running start sealert.

If it is running display the browser and make sure the alert you are expecting is not filtered

Note alert notification only occurs when the alert arrives, but the alert should be visible in the browser.

If all of these things fail then setroubleshoot may be experiencing technical difficulties, check the logs for error messages.

How is sealert started?

sealert is configured to start with your login session. It should be running after you login. If you've just installed the sealert RPM you may need to start the setroubleshoot service (see above) and logout and back in again to start sealert. Or you can manually start sealert with this command:

% sealert -s

Note: when you start sealart with the -s option you're telling it to start as a desktop session service. It runs in the background and does not display anything until an alert arrives from the setroubleshoot daemon. If you want the browser to appear when you start sealert use the -b option instead.

How do I display the alert browser?

There are 3 ways to display the alert browser:

  1. From the menu 'System --> Administration --> SELinux Troubleshooter
  1. If the setroubleshoot icon is showing in the status area, you can

click on it.

  1. From the command line, use the command 'sealert -b'

Note: sealert runs continuously in the background as a desktop session service. When you use the sealert -b option to display the browser or use the System --> Administration menu (which simply runs sealert -b) a message is sent to the running copy of sealert asking it to display the alert browser, if the sealert service is not running it will be started first. The command 'sealert -b' sends the message and exits.

Does sealert run continuously?

When run as a normal desktop tool sealert runs continuously. Even when you close the sealert browser window the process continues to run in the background. The reason why it does this is because it is quietly waiting for a AVC alert from the setroubleshoot service daemon.

Should it recieve a message from the daemon it will put up the status icon and notification message and wait for you to click on the icon to view the message. However, if you have filtered the AVC (told setroubleshoot you don't want to be bothered with a particular alert) then sealert will not notify you.

Follow these instructions to stop sealert.

How can I stop sealert?

If you want to stop the sealert service do this:

% sealert -q

This sends a message to the running sealert service and asks it to quit.

Some alerts are meaningful to me, others are just an annoyance, can I filter them somehow?

Yes. Open the alert browser, find the alert you which to ignore and click the 'filter' checkbox associated with the alert. You will no longer be notified of these alerts. Later if you wish you can uncheck the filter box and you will get alerts again.

Please note, if you permanently delete an alert setroubleshoot permanently forgets everything about the alert, including your desire to filter it. If the alert repeats again after you've deleted it previously you'll have to click the filter box again.

TIP: You can mark an alert for deletion and then hide all alerts marked for deletion. This is one way to continue to filter an alert but not have it appear in the alert browser.

Does setroubleshoot have a log I can check?

Yes. The setroubleshootd daemon and the sealert user tool are seperate processes and have seperate logging.

The setroubleshoot daemon logs its operations to /var/log/setroubleshoot/setroubleshootd.log.

The sealert user tool does not log by default, but you can get it log by editing the config file.

By default it only logs warnings and errors. Error messages are also written to the standard syslog (/var/log/messages).

You can change the verbosity of the logging messages by editing the config file.

The config file has two sections in it for logging, one for each process: [sealert_log] [setroubleshootd_log]

Find the section you wish to modify, there are a number of options, most of which are documented in the config file. The 'level' option changes the verbosity, setting the level to 'debug' is a good choice if your trying to diagnose a problem. The 'filename' option sets the file where logging will be directed. If no file is set logging goes to the console. By default there is no file set for sealert because its a per user log file and by default we don't want to be writing user files. The 'console' flag will also send logging messages to the console if otherwise they are also being writtin to a log file (if there is no log file, messages are directed to the console). There is also a 'categories' list which will allow you to select functional areas to log. By default all categories are logged.

Does setroubleshoot have a config file?

Yes. /etc/setroubleshoot/setroubleshoot.cfg

The format of the config file is a standard 'ini' divided into sections. Each section is labeled inside square brackets, e.g. all the email related options are in the section [email].

Most entries in the file are documented directly above the option.

The config file is read when the process (setroubleshootd or sealert) is started. If you change the config file you'll have to restart the process.

How do I switch which alerts I'm viewing?

Alerts are always collected into an alert database (see What is an alert). There is an alert database for collecting alerts from the audit subsystem, an alert database for any log files which were scanned, etc. You can use the View menu to select which database the browser is visiting (e.g. viewing). The alert database currently being visited (viewed) is displayed in the [#sealert-statusbar status bar].

What is an alert?

An alert is a general description of something SELinux prevented. It is not a specific instance of a SELinux denial. This is because in almost all cases users are most interested in a "problem" such as "the web server can't read home directories" as well as how often that "problem" is occurring. An alert is the general problem describing a SELinux denial. Alerts may have multiple instances, e.g. this problem occurred 15 times.

An alert is the linking of a general denial with analysis information and any metadata such as [#alert-environment-info environmental information], time stamps, occurance counts, etc.

Every time a denial event is recognized it is converted to an alert signature, a general way of describing the denial event. Then the alert database is consulted to see if the denial has been seen before, if so its report count is incremented, otherwise it's added to the database. Irregardless of whether the denial was previously in the alert database or not a full analysis is run on the denial event to produce a [#analysis-report analysis report]. The most recent analysis report of the denial event is stored in the alert database along with how many times it occurred and when it last occurred. This means the description of the denial event (e.g. the analysis-report is based on the most recent occurrence of the denial event.

What is an AVC message?

The kernel audit subsystem emits a message whenever SELinux denies permission (or would have denied permission). These messages describe the particulars of what the kernel is doing at the moment and is not a complete desciption of the denial (which we term [#denial-event denial event]. As the kernel continues to process the system call which triggered the AVC additional messages may be emitted independently which when combined fully describe the denial event. Thus any one AVC message may be an incomplete description of the denial event. Each AVC message is tagged with the denial event it is part of and post processiong tools such as setroubleshoot can assemble independent AVC messages into complete events.

What is a Denial Event?

A denial event is exactly one operation SELinux denied. It may be reported by the kernel as multiple [#avc-message AVC messages]. Specialized software such as setroubleshoot has the ability to merge independent AVC messages into single denial events. People often use the term AVC when they really mean denial event.

setroubleshoot uses a general method to "label" [#denial-event denial events] called an alert signature.

What is environment information and why is it sometimes missing?

Environment infomation describes the "context" in which the denial event occurred. It is the information most useful for rectifying a problem, filing a bug report etc. It lists items such as the version of the SELinux policy, the version of the operating system, the RPM package and version the software which triggered the denial came from, etc.

However envionmental information can only be reliably gathered at the moment the denial occurred. If one queried the system for environmental information at a later point in time, for instance during log file scanning, then the enviroment may have changed in the interim which would then attach incorrect infomation to the alert. The same problem occurs if the log file being scanned was generated on another system.

Therefore environment information by default is only gathered when alerts enter the system via real time audit monitoring (e.g. audit listener). This is the only time enviroment information is guaranteed to be correct. Alerts generated from log file scans do not display environment information.

What is an alert database?

A general denial (as opposed to a specific instance of the denial) is described by its signature. Alert databases store information about a denial such as its analysis, how many times this denial has occurred, when was the first and most recent time it was reported, etc. The alert is looked up in the database by its signature.

What is an alert signatures?

Alert signatures are a means to describe a general denial. For most users this can be thought of as an "SELinux problem" such as "the web server can't execute CGI scripts". A signature collects the minimal information necessary to uniquely descibe a SELinux denial, but no more information than is necessary otherwise the signature would begin to describe specific instances rather than a general problem. However the content of the signature must be unique enough so that denial events which are fundamentally unique are not coalesced into a single description.

Signatures allow alerts to be "portable" across systems. For example if you're managing a collection of nodes the same signature can be used to reference the same problem on all the nodes. As a system administrator it is quite useful to see nodes X,Y, and Z are all showing the same problem, but node W is not. Portable signatures also make bug reporting much more useful because one signature can be used for every person reporting the same problem.

Alerts are always referenced by their signature. In essence an alert is the alert analysis and metadata which is looked up by its signature in the alert database.

What is an analysis report?

When a denial event enters the system for analysis each analysis plugin is given an opportunity to examine the denial event. If the plugin recognizes the denial event it creates an analysis report providing as much information as it can about the event such as a summmary, a detailed description, how one might fix the problem, etc. The analysis report is the bulk of the information presented to the user when he or she views an alert. The analysis report may optionally be merged with [#alert-environment-info environmental information].

Can I delete alerts?

Yes. The alert browser is modeled after an email IMAP client which may be familiar. Deletion is a two step process. First an alert is marked for deletion. This is done by selecting one or more alerts in the alert list and choosing the "Mark Delete" option from either the Edit menu or the right-click popup menu. At this point the alert is not actually deleted, it is just marked as pending for deletion, this is indicated by drawing a strike-out line through the alert. One can hide alerts marked for deletion.

To permanently delete the alerts marked for deletion choose the "Remove All Marked for Deletion" command from either the Edit menu or the right-click popup menu.

Can I hide alerts marked for deletion?

Yes. Use the View menu and toggle the "Hide Deleted" option. Alerts marked for deletion will not be visible in the alert list. They will remain in the alert database until the "Remove All Marked for Deletion" command is executed. You may toggle the hide option on and off.

Are there shortcuts for common operations in the browser?

Yes, right clicking in the browser alert list will bring up a popup menu with common commands.