client.conf(5)

NAME
client.conf - client configuration file for cups (deprecated on macos)

DESCRIPTION
The client.conf file configures the CUPS client and is normally located in the /etc/cups and/or ~/.cups directories. Each line in the file can be a configuration directive, a blank line, or a comment. Comment lines start with the # character.

Note: Starting with macOS 10.7, this file is only used by command-line and X11 applications plus the IPP backend. The ServerName directive is not supported on macOS at all. Starting with macOS 10.12, all applications can access these settings in the /Library/Preferences/org.cups.PrintingPrefs.plist file instead. See the NOTES section below for more information.

  DIRECTIVES
The following directives are understood by the client. Consult the online help for detailed descriptions:

AllowAnyRoot Yes

AllowAnyRoot No
    Specifies whether to allow TLS with certificates that have not been signed by a trusted Certificate Authority. The default is "Yes".

AllowExpiredCerts Yes

AllowExpiredCerts No
    Specifies whether to allow TLS with expired certificates. The default is "No".

DigestOptions DenyMD5

DigestOptions None
    Specifies HTTP Digest authentication options. DenyMD5 disables support for the original MD5 hash algorithm.

Encryption IfRequested

Encryption Never

Encryption Required
    Specifies the level of encryption that should be used.

GSSServiceName name
    Specifies the Kerberos service name that is used for authentication, typically "host", "http", or "ipp". CUPS adds the remote hostname ("name@server.example.com") for you. The default name is "http".

ServerName hostname-or-ip-address[:port]

ServerName /domain/socket
    Specifies the address and optionally the port to use when connecting to the server. Note: This directive is not supported on macOS 10.7 or later.

ServerName hostname-or-ip-address[:port]/version=1.1
    Specifies the address and optionally the port to use when connecting to a server running CUPS 1.3.12 and earlier.

SSLOptions [AllowDH] [AllowRC4] [AllowSSL3] [DenyCBC] [DenyTLS1.0] [MaxTLS1.0] [MaxTLS1.1] [MaxTLS1.2] [MaxTLS1.3] [MinTLS1.0] [MinTLS1.1] [MinTLS1.2] [MinTLS1.3] [NoSystem]

SSLOptions None
    Sets encryption options (only in /etc/cups/client.conf). By default, CUPS only supports encryption using TLS v1.0 or higher using known secure cipher suites. Security is reduced when Allow options are used. Security is enhanced when Deny options are used. The AllowDH option enables cipher suites using plain Diffie-Hellman key negotiation (not supported on systems using GNU TLS). The AllowRC4 option enables the 128-bit RC4 cipher suites, which are required for some older clients. The AllowSSL3 option enables SSL v3.0, which is required for some older clients that do not support TLS v1.0. The DenyCBC option disables all CBC cipher suites. The DenyTLS1.0 option disables TLS v1.0 support - this sets the minimum protocol version to TLS v1.1. The MinTLS options set the minimum TLS version to support. The MaxTLS options set the maximum TLS version to support. The NoSystem option disables applying system cryptographic policy. Not all operating systems support TLS 1.3 at this time.

TrustOnFirstUse Yes

TrustOnFirstUse No
    Specifies whether to trust new TLS certificates by default. The default is "Yes".

User name
    Specifies the default user name to use for requests.

UserAgentTokens None

UserAgentTokens ProductOnly

UserAgentTokens Major

UserAgentTokens Minor

UserAgentTokens Minimal

UserAgentTokens OS

UserAgentTokens Full
    Specifies what information is included in the User-Agent header of HTTP requests. "None" disables the User-Agent header. "ProductOnly" reports "CUPS". "Major" reports "CUPS/major IPP/2". "Minor" reports "CUPS/major.minor IPP/2.1". "Minimal" reports "CUPS/major.minor.patch IPP/2.1". "OS" reports "CUPS/major.minor.path (osname osversion) IPP/2.1". "Full" reports "CUPS/major.minor.path (osname osversion; architecture) IPP/2.1". The default is "Minimal".

ValidateCerts Yes

ValidateCerts No
    Specifies whether to only allow TLS with certificates whose common name matches the hostname. The default is "No".

NOTES
The client.conf file is deprecated on macOS and will no longer be supported in a future version of CUPS. Configuration settings can instead be viewed or changed using the defaults(1) command:
defaults write /Library/Preferences/org.cups.PrintingPrefs.plist Encryption Required
defaults write /Library/Preferences/org.cups.PrintingPrefs.plist TrustOnFirstUse -bool NO
defaults read /Library/Preferences/org.cups.PrintingPrefs.plist Encryption
On Linux and other systems using GNU TLS, the /etc/cups/ssl/site.crl file, if present, provides a list of revoked X.509 certificates and is used when validating certificates.

SEE ALSO
cups(1), default(1), CUPS Online Help (http://localhost:631/help)

COPYRIGHT
Copyright © 2020-2025 by OpenPrinting.