General-Purpose Mail Package
|Official GNU Software|
Mailutils debugging output is controlled by a set of levels, each of
which can be set independently of others. Each debug level consists of
a category name, which identifies the part of
Mailutils for which additional debugging is desired, and a
level number, which tells
Mailutils how verbose should its
Valid debug levels are:
Displays error conditions which are normally not reported, but passed to the caller layers for handling.
Ten levels of verbosity, ‘trace0’ producing less output, ‘trace9’ producing the maximum amount of output.
Displays network protocol interaction, where applicable.
Implementation and applicability of each level differs between various categories. The full list of categories is available in file libmailutils/diag/debcat in the Mailutils source tree. Most useful categories and levels implemented for them are discussed later in this article.
Debug levels can be set either from the command line, by using the --debug-level command line option, or from the configuration file, using the ‘.debug.level’ statement. In both cases, the level is specified as a list of individual levels, delimited with semicolons. Each individual level can be specified as:
Disables all levels for the specified category.
Enables all levels for the specified category.
For the given category, enables all levels from ‘error’ to level, inclusive.
Enables only the given level for this category.
Disables all levels from ‘error’ to level, inclusive, for this category.
Disables only the given level in this category.
Enables all levels in the range from levelA to levelB, inclusive.
Disables all levels in the range from levelA to levelB, inclusive.
Additionally, a comma-separated list of level specifications is allowed after the dot. For example, the following specification:
enables in category ‘acl’ all levels, except ‘trace9’, ‘trace0’, ‘trace1’, and ‘trace2’.
The following specification in Backus-Naur form describes formally the Mailutils debug level:
<debug-spec> ::= <level-spec> | <debug-level-list> <debug-level-list> ::= <debug-level> | <debug-level-list> ";" <debug-level> <debug-level> ::= <category> | "!" <category> | <category> "." <level-list> <level-list> ::= <level-spec> | <level-list> "," <level-spec> <level-spec> ::= <level> | <negate-level> <negate-level> ::= "!" <level> <level> ::= <level-number> | "=" <level-number> | <level-number> "-" <level-number> <level-number> ::= "error" | "trace0" | "trace1" | "trace2" | "trace3" | "trace4" | "trace5" | "trace6" | "trace7" | "trace8" | "trace9" | "prot"
This category enables debugging of Access Control Lists. Available levels are:
As usual, displays errors, not directly reported otherwise.
Basic tracing of ACL processing.
Traces the process of matching the ACL conditions.
This category affects configuration parser and/or lexical analyzer. The following levels are supported:
Minimal information about configuration statements.
Trace lexical structure of the configuration files.
Trace execution of the configuration parser.
Due to its specific nature, this category cannot be enabled from the configuration file. A special hook is provided to facilitate debugging the configuration parser, namely, a pragmatic comment in form:
causes debug-level-list to be parsed as described above. Thus, to force debugging of the configuration parser, one would add the following line at the very beginning of the configuration file:
Operations over mailboxes. This module supports the following levels: ‘error’, ‘trace0’, ‘trace1’, and ‘prot’. The latter is used by remote mailbox support libraries.
Enables debugging information about authentication and authorization. This category supports the following levels: ‘error’, ‘trace0’, ‘trace1’, and ‘trace2’.
In level ‘trace0’, user data are reported along with the data source they were obtained from. The output may look like this:
pop3d: source=system, name=gray, passwd=x, uid=120, gid=100, gecos=Sergey Poznyakoff, dir=/home/gray, shell=/bin/bash, mailbox=/var/mail/gray, quota=0, change_uid=1
In the ‘trace1’ level, additional flow traces are displayed.
In the level ‘trace2’, a detailed flow trace is displayed, which looks like the following:
pop3d: Trying generic... pop3d: generic yields 38=Function not implemented pop3d: Trying system... pop3d: system yields 0=Success pop3d: Trying generic... pop3d: generic yields 4135=Authentication failed pop3d: Trying system... pop3d: system yields 0=Success
Debugs mailer operations. The following levels are supported:
Displays mild error conditions.
Traces mailer operations in general: displays what part of the message is being sent, etc.
When used together with ‘prot’, displays security-sensitive information (such as passwords, user keys, etc). in plaintext. By default, such information is replaced with asterisks to reduce the possibility of security compromise.
When used together with ‘prot’, displays the payload information as it is being sent. The payload is the actual message contents, i.e. the part of SMTP transaction that goes after the ‘DATA’ command and which ends with a terminating dot line. Setting this level can generate huge amounts of information.
For SMTP mailer: outputs transcripts of SMTP sessions.
Note: Unless in a very secure environment, it is advised to avoid using level settings such as mailer.prot or mailer (without explicit level part), because the resulting output tends to be extremely copious and reveals sender private and security-sensitive data. If you wish to trace SMTP session flow, use ‘mailer.=prot’ or at least ‘mailer.prot,!trace6’.
This category provides debugging information for Mailutils IP server objects. It supports the ‘error’ and ‘trace0’ levels.
This category controls debugging information shown for operations related to Mailutils folders.
The remote category is used by
servers to request showing additional information in the session
transcripts. This category takes effect only when the
configuration variable is set. Valid levels are:
Show security-sensitive information (user passwords, etc.)
Show payload information
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