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Configuring the Size and Number of Log Files

To prevent log files from growing too large, the JUNOS system logging utility by default writes messages to a sequence of files of a defined size. The files in the sequence are referred to as archive files to distinguish them from the active file to which messages are currently being written. The default maximum size depends on the platform type:

  • 128 kilobytes (KB) for J Series Services Routers
  • 1 megabyte (MB) for M Series, MX Series, and T Series routing platforms

When an active log file called logfile reaches the maximum size, the logging utility closes the file, compresses it, and names the compressed archive file logfile.0.gz. The logging utility then opens and writes to a new active file called logfile. When the new logfile reaches the configured maximum size,logfile.0.gz is renamed logfile.1.gz, and the new logfile is closed, compressed, and renamed logfile.0.gz. By default, the logging utility creates up to 10 archive files in this manner. When the maximum number of archive files is reached, each time the active file reaches the maximum size the contents of the oldest archive file are lost (overwritten by the next oldest file). The logging utility by default also limits the users who can read log files to the root user and users who have the JUNOS maintenance permission.

You can include the archive statement to change the maximum size of each file, how many archive files are created, and who can read log files. To configure values that apply to all log files, include the archive statement at the [edit system syslog] hierarchy level:

[edit system syslog]
archive {
	files number;
	size size;
	(world-readable | no-world-readable);
}

To configure values that apply to a particular log file, include the archive statement at the [edit system syslog file filename] hierarchy level:

[edit system syslog file filename]
facility severity;
archive {
	files number;
	size size;
	(world-readable | no-world-readable);
}

files number specifies the number of files to create before the oldest file is overwritten. The value can be from 1 through 1000.

size size specifies the maximum size of each file. The value can be from 64 KB (64k) through 1 gigabyte (1g); to represent megabytes, use the letter m after the integer. There is no space between the digits and the k, m, or g units letter.

world-readable enables all users to read log files. To restore the default permissions, include the no-world-readable statement.


Published: 2010-04-28

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