client.conf - client configuration file for cups
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.
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
- 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 ("firstname.lastname@example.org") 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
- 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]
- 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
- TrustOnFirstUse Yes
- TrustOnFirstUse No
- Specifies whether to trust new TLS certificates by default. The default is
- User name
- Specifies the default user name to use for requests.
- ValidateCerts Yes
- ValidateCerts No
- Specifies whether to only allow TLS with certificates whose common name
matches the hostname. The default is "No".
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.
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