The available levels, in order from most to least critical are emerg , alert , crit , err , warning , notice , info , and debug. The facilities, in no particular order, are auth , authpriv , console , cron , daemon , ftp , kern , lpr , mail , mark , news , security , syslog , user , uucp , and local0 through local7.
Be aware that other operating systems might have different facilities. For more information about the different levels and facilities, refer to syslog 3 and syslogd 8. Log files can grow quickly, taking up disk space and making it more difficult to locate useful information. Log management attempts to mitigate this. In FreeBSD, newsyslog is used to manage log files.
This built-in program periodically rotates and compresses log files, and optionally creates missing log files and signals programs when log files are moved.
The log files may be generated by syslogd or by any other program which generates log files. While newsyslog is normally run from cron 8 , it is not a system daemon. In the default configuration, it runs every hour.
This file contains one line for each log file that newsyslog manages. Each line states the file owner, permissions, when to rotate that file, optional flags that affect log rotation, such as compression, and programs to signal when the log is rotated.
Here is the default configuration in FreeBSD:. Each line starts with the name of the log to be rotated, optionally followed by an owner and group for both rotated and newly created files.
The mode field sets the permissions on the log file and count denotes how many rotated log files should be kept. The size and when fields tell newsyslog when to rotate the file. A log file is rotated when either its size is larger than the size field or when the time in the when field has passed. The flags field gives further instructions, such as how to compress the rotated file or to create the log file if it is missing. The last two fields are optional and specify the name of the Process ID PID file of a process and a signal number to send to that process when the file is rotated.
For more information on all fields, valid flags, and how to specify the rotation time, refer to newsyslog. Since newsyslog is run from cron 8 , it cannot rotate files more often than it is scheduled to run from cron 8. Monitoring the log files of multiple hosts can become unwieldy as the number of systems increases.
Configuring centralized logging can reduce some of the administrative burden of log file administration. In FreeBSD, centralized log file aggregation, merging, and rotation can be configured using syslogd and newsyslog. This section demonstrates an example configuration, where host A , named logserv. Host B , named logclient. A log server is a system that has been configured to accept logging information from other hosts. Before configuring a log server, check the following:.
If there is a firewall between the logging server and any logging clients, ensure that the firewall ruleset allows UDP port for both the clients and the server. The logging server and all client machines must have forward and reverse entries in the local DNS. Proper name resolution is required so that log entries are not rejected by the logging server. When adding multiple log clients, add a similar two-line entry for each client.
More information about the available facilities may be found in syslog. The first entry starts syslogd at system boot. The second entry allows log entries from the specified client. The -v -v increases the verbosity of logged messages. This is useful for tweaking facilities as administrators are able to see what type of messages are being logged under each facility.
Multiple -a options may be specified to allow logging from multiple clients. IP addresses and whole netblocks may also be specified. Refer to syslogd 8 for a full list of possible options. If a PID is returned, the server restarted successfully, and client configuration can begin. A logging client sends log entries to a logging server on the network.
The client also keeps a local copy of its own logs. The first entry enables syslogd on boot up. The second entry prevents logs from being accepted by this client from other hosts -s and increases the verbosity of logged messages.
In this example, all logged facilities are sent to a remote system, denoted by the symbol, with the specified hostname:. To test that log messages are being sent across the network, use logger 1 on the client to send a message to syslogd:. If no messages are being received on the log server, the cause is most likely a network connectivity issue, a hostname resolution issue, or a typo in a configuration file. Repeat until the ping is successful from both hosts.
If the ping succeeds on both hosts but log messages are still not being received, temporarily increase logging verbosity to narrow down the configuration issue. In this example, the log messages are being rejected due to a typo which results in a hostname mismatch. Fix the typo, issue a restart, and verify the results:. As with any network service, security requirements should be considered before implementing a logging server. Log files may contain sensitive data about services enabled on the local host, user accounts, and configuration data.
Network data sent from the client to the server will not be encrypted or password protected. Local security is also an issue. Log files are not encrypted during use or after log rotation.
Local users may access log files to gain additional insight into system configuration. Setting proper permissions on log files is critical. The built-in log rotator, newsyslog, supports setting permissions on newly created and rotated log files. Setting log files to mode should prevent unwanted access by local users.
Refer to newsyslog. Extra sendmail 8 configuration and other MTA configuration files. Configuration files for installed applications. May contain per-application subdirectories. Automatically generated system-specific database files, such as the package database and the locate 1 database. The IP address of a name server the resolver should query. The servers are queried in the order listed with a maximum of three. Search list for hostname lookup. This is normally determined by the domain of the local hostname.
Entries for local computers connected via a LAN can be added to this file for simplistic naming purposes instead of setting up a named 8 server. Consult hosts 5 for more information. Over five hundred system variables can be read and set using sysctl 8. At its core, sysctl 8 serves two functions: to read and to modify system settings.
Settings of sysctl variables are usually either strings, numbers, or booleans, where a boolean is 1 for yes or 0 for no. For more information, refer to sysctl. The specified values are set after the system goes into multi-user mode. Not all variables are settable in this mode. In some cases it may be desirable to modify read-only sysctl 8 values, which will require a reboot of the system. For instance, on some laptop models the cardbus 4 device will not probe memory ranges and will fail with errors similar to:.
The fix requires the modification of a read-only sysctl 8 setting. Add hw. Now cardbus 4 should work properly. The following section will discuss various tuning mechanisms and options which may be applied to disk devices. In many cases, disks with mechanical parts, such as SCSI drives, will be the bottleneck driving down the overall system performance.
While a solution is to install a drive without mechanical parts, such as a solid state drive, mechanical drives are not going away anytime in the near future. When tuning disks, it is advisable to utilize the features of the iostat 8 command to test various changes to the system.
This command will allow the user to obtain valuable information on system IO. The vfs. It is set to 1 by default. This variable controls how directories are cached by the system.
Most directories are small, using just a single fragment typically 1 K in the file system and typically bytes in the buffer cache. With this variable turned off, the buffer cache will only cache a fixed number of directories, even if the system has a huge amount of memory. When turned on, this sysctl 8 allows the buffer cache to use the VM page cache to cache the directories, making all the memory available for caching directories. However, the minimum in-core memory used to cache a directory is the physical page size typically 4 K rather than bytes.
Keeping this option enabled is recommended if the system is running any services which manipulate large numbers of files. Such services can include web caches, large mail systems, and news systems. Keeping this option on will generally not reduce performance, even with the wasted memory, but one should experiment to find out. This tells the file system to issue media writes as full clusters are collected, which typically occurs when writing large sequential files.
However, this may stall processes and under certain circumstances should be turned off. The default is usually sufficient, but on machines with many disks, try bumping it up to four or five megabytes.
Do not set this value arbitrarily high as higher write values may add latency to reads occurring at the same time. There are various other buffer cache and VM page cache related sysctl 8 values. Modifying these values is not recommended as the VM system does a good job of automatically tuning itself.
The vm. Such systems tend to generate continuous pressure on free memory reserves. Turning this feature on and tweaking the swapout hysteresis in idle seconds via vm. This gives a helping hand to the pageout daemon. Only turn this option on if needed, because the tradeoff is essentially pre-page memory sooner rather than later which eats more swap and disk bandwidth. In a small system this option will have a determinable effect, but in a large system that is already doing moderate paging, this option allows the VM system to stage whole processes into and out of memory easily.
Turning off IDE write caching reduces write bandwidth to IDE disks, but may sometimes be necessary due to data consistency issues introduced by hard drive vendors. The problem is that some IDE drives lie about when a write completes. With IDE write caching turned on, IDE hard drives write data to disk out of order and will sometimes delay writing some blocks indefinitely when under heavy disk load.
A crash or power failure may cause serious file system corruption. Check the default on the system by observing the hw. For more information, refer to ata 4. The defaults are fairly high and can be responsible for 15 seconds of delay in the boot process.
Reducing it to 5 seconds usually works with modern drives. The kern. The tunable and kernel configuration option accept values in terms of milliseconds and not seconds.
To fine-tune a file system, use tunefs 8. This program has many different options. To toggle Soft Updates on and off, use:. A file system cannot be modified with tunefs 8 while it is mounted. A good time to enable Soft Updates is before any partitions have been mounted, in single-user mode. Soft Updates is recommended for UFS file systems as it drastically improves meta-data performance, mainly file creation and deletion, through the use of a memory cache.
There are two downsides to Soft Updates to be aware of. First, Soft Updates guarantee file system consistency in the case of a crash, but could easily be several seconds or even a minute behind updating the physical disk. If the system crashes, unwritten data may be lost. Secondly, Soft Updates delay the freeing of file system blocks. If the root file system is almost full, performing a major update, such as make installworld , can cause the file system to run out of space and the update to fail.
Meta-data updates are updates to non-content data like inodes or directories. Historically, the default behavior was to write out meta-data updates synchronously. If a directory changed, the system waited until the change was actually written to disk. The file data buffers file contents were passed through the buffer cache and backed up to disk later on asynchronously.
The advantage of this implementation is that it operates safely. If there is a failure during an update, meta-data is always in a consistent state. A file is either created completely or not at all. If the data blocks of a file did not find their way out of the buffer cache onto the disk by the time of the crash, fsck 8 recognizes this and repairs the file system by setting the file length to 0.
Additionally, the implementation is clear and simple. The disadvantage is that meta-data changes are slow. For example, rm -r touches all the files in a directory sequentially, but each directory change will be written synchronously to the disk. This includes updates to the directory itself, to the inode table, and possibly to indirect blocks allocated by the file. Similar considerations apply for unrolling large hierarchies using tar -x.
The second approach is to use asynchronous meta-data updates. This is the default for a UFS file system mounted with mount -o async. Since all meta-data updates are also passed through the buffer cache, they will be intermixed with the updates of the file content data.
The advantage of this implementation is there is no need to wait until each meta-data update has been written to disk, so all operations which cause huge amounts of meta-data updates work much faster than in the synchronous case.
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In this Section:. MEM and Packet. PKT logs are not supported. You may comment out some of the log configurations that you do not want to copy to the syslog server for example, the entries corresponding to mails. The system administrator of the remote syslog server deploy tools for managing the logs received by the servers.
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