dbclean(8)

📦 version 2.3.169, in alpine 3.24

💖 dbclean(8) — Clean Distributed Checksum Clearinghouse Database 💖

okay bestie, welcome to the System Manager's Manual page for dbclean(8) — yes, the one and only DCC database cleaner. Pull up a chair, hydrate, and let's get into it 💅

✨ NAME ✨

dbclean — Clean Distributed Checksum Clearinghouse Database

🦋 SYNOPSIS 🦋

dbclean [-dfFNPSVqu] [-i id] [-a [server-addr][,port]] [-h homedir]
        [-H hash-file-dir] [-D db-file-dir] [-G on] [-R mode]
        [-s hash-size] [-e seconds] [-E spamsecs]
        [-L ltype,facility.level]

🌸 DESCRIPTION 🌸

okay so dbclean is the main character here: it creates empty databases, rebuilds corrupted ones, and deletes or expires old reports of checksums from DCC databases. iconic behavior, honestly 🫶

It should be installed where it will be found with the path given the DCC server daemon when the daemon needs to expand the hash table. See dccd(8). It should also be run by the daily cron(8) job, /usr/libexec/cron-dccd.

The whitelist in /var/dcc/whitelist or /var/dcc/grey_whitelist is built into the DCC server's database. Changes to the whitelist are not effective until dbclean is run. White or blacklists can also be used by DCC clients and work better.

💅 OPTIONS 💅

The following options are available. Most of them should be set by changing DBCLEAN_LOGDAYS and DBCLEAN_ARGS in the /var/dcc/dcc_conf control file.

  • -d — enables debugging output. Additional -d options increase the number of messages.
  • -F — uses write() instead of mmap() and msync() in some cases to modify the DCC database. This works better on some versions of Solaris provided the entire DCC database fits in RAM and provided the file system has not been tuned for the large, random accesses of a DCC database. It is the default on Solaris except when the database is in a memory mapped file system or the entire database fits in RAM. Do not use -F with -f, -H, or -D.
  • -f — uses mmap() and msync() to modify the DCC database. Do not use -f with -F, -H, or -D.
  • -N — creates a new, empty database. There must not be an existing database and the DCC server, dccd(8), must not be running.
  • -P — expires old checksums from a database using the -e -and -E values from the preceding use of dbclean. -P cannot be used with -e or -E. Using -P differs from not using -e or -E, because in the absence of all three, their default values are used.
  • -S — says that the DCC server, dccd(8), is not running and so dbclean should run stand-alone and not try to tell the DCC server about changes to the database. -i is not needed with -S.
  • -V — displays the version of the DCC database cleaner. Two or more -V options show the options with which it was built.
  • -q — quiets the announcement to stderr of the final results and debugging messages turned on with -d. Results are still sent to the system log.
  • -u — should be used when the file system containing the dcc_db and dcc_db.hash files is "ultra-fast," such as a solid-state drive. This setting postpones writing some data during normal operation until the system is shutdown. This reduces wear on the SSD at the cost of writing GBytes of data when the system is shutdown. Writing GBytes to a rotating disk at system shutdown is unacceptable, but not noticeable to a non-rotating disk that operates 10 or 100 times faster.
  • -i id — specifies the DCC ID recognized by the local DCC server as its own. This ID allows the DCC server to recognize commands from dbclean to stop using the database while it is being cleaned.
  • -a [server-addr][,port] — is commonly used to specify a UDP port or IP address of the local server other than the default.
  • -h homedir — overrides the default DCC home directory, /var/dcc.
  • -H hash-file-dir — puts the dcc_db.hash hash table file in the hash-file-dir directory with a symbolic link. Using -H to put the hash table in a memory, "tmpfs", or "swap" file system such as /dev/shm or /tmp significantly speeds up the DCC server, dccd(8), on operating systems such as Linux and Solaris that lack the MAP_NOSYNC flag for the mmap(8) system call.

The memory file system must have space for two copies of the dcc_db.hash file. -H is undesirable on FreeBSD and other systems with MAP_NOSYNC except when -D is used. The DCC database file, dcc_db, should usually be in a file system that is not cleared by operating system rebooting and not in a memory file system.

Use or stop using -H by adding it to or removing it from DBCLEAN_ARGS in /var/dcc/dcc_conf and manually running or waiting for the nightly run of the /usr/libexec/cron-dccd cron job.

Do not use -H with -F or -f.

  • -D db-file-dir — puts the /var/dcc/dcc_db database and the /var/dcc/dcc_db.hash hash table files in the db-file-dir directory with symbolic links. Using -D to put the files in a memory, "tmpfs", or "swap" file system such as /dev/shm or /tmp significantly speeds up the DCC server, dccd(8), but causes several GBytes of database transfers before DCC is effective whenever the operating system is restarted. -D should not be used except at sites with more than one DCC server installation and where at least one of the other local servers is not using -D. -D should only be used on systems that are rarely rebooted, because up to one month is required for the database to reach equilibrium.

The memory file system must have space for two copies of the dcc_db file.

Use or stop using -D by adding it to or removing it from DBCLEAN_ARGS in /var/dcc/dcc_conf and manually running or waiting for the nightly run of the /usr/libexec/cron-dccd cron job.

Do not use -D with -F or -f.

  • -G on — cleans a greylist database in /var/dcc/grey_db and /var/dcc/grey_db.hash instead of a DCC server database.
  • -R mode — repairs a database or does a quick cleaning. Mode must be one of the following:
    • bad — to repair a broken database.
    • quick — for a quick, superficial cleaning during the day.
    • hash — to rebuild a hash not sent to disk before the system was rebooted.
    • failsafe — to work around missing nightly cleaning by the cron(8) job, /usr/libexec/cron-dccd.
    • del — to finish processing a delete command received by dccd(8).
  • -s hash-size — specifies a size for the hash table in /var/dcc/dcc_db.hash. By default the hash table is rebuilt to be approximately 80% full based on an estimate of the number of distinct checksums in the database file.
  • -e seconds — specifies that reports older than seconds and with totals below 10 targets should be deleted. Reports older than seconds of checksums that have been reported more recently are summarized in the database. The default value is 1DAY or the value of -E, whichever is smaller. The 1 day default is reduced if the system does not appear to have enough RAM to hold the database. The minimum is 1 hour. Seconds can also be NEVER or a number of hours, days, or weeks followed by HOURS, H, DAYS, D, WEEKS or W.

DCC servers that are not very busy and are isolated or do not receive "floods" of checksums from busy servers should use longer values to increase their chances of recognizing bulk mail.

  • -E spamsecs — changes the expiration of checksums with more than 10 targets from the default of 30DAYS or the explicit value of -e, whichever is larger. The default is reduced if the system does not have enough RAM to hold the database. Spamsecs can also be NEVER or a number of hours, days, or weeks followed by HOURS, H, DAYS, D, WEEKS or W.
  • -L ltype,facility.level — specifies how messages should be logged. Ltype must be error, info, or off to indicate which of the two types of messages are being controlled or to turn off all syslog(3) messages from dbclean. Level must be a syslog(3) level among EMERG, ALERT, CRIT, ERR, WARNING, NOTICE, INFO, and DEBUG. Facility must be among AUTH, AUTHPRIV, CRON, DAEMON, FTP, KERN, LPR, MAIL, NEWS, USER, UUCP, and LOCAL0 through LOCAL7. The default is equivalent to -L info,MAIL.NOTICE -L error,MAIL.ERR.

dbclean exits 0 on success, and > 0 if an error occurs.

🎀 FILES 🎀

  • /var/dcc — is the DCC home directory containing data and control files.
  • dcc_conf — is the DCC control file.
  • dcc_db — is the main file containing mail checksums.
  • dcc_db.hash — mail checksum database hash table.
  • grey_db — is the database of greylist checksums.
  • grey_db.hash — is the greylist database hash table.
  • dcc_db-new, dcc_db-new.hash, grey_db-new, grey_db-new.hash — new database and hash files until they are renamed.
  • dcc_db-old, grey_db-old — previous database files.
  • ids — list of IDs and passwords, as described in dccd(8).
  • whitelist — contains the DCC server whitelist in the format described in dcc(8).
  • grey_whitelist — contains the greylist server whitelist.

🌈 SEE ALSO 🌈

okay bestie, go read these too:

⭐ HISTORY ⭐

Implementation of dbclean was started at Rhyolite Software, in 2000. This document describes version RHYOLITE_VERSION.

💅 that's the whole page, bestie — source/version: RHYOLITE_VERSION (Rhyolite Software), date: March 22, 2024, and yes it's the System Manager's Manual. mwah 💖

📦 where this page comes from