+.B PORTAGE_BINPKG_FORMAT
+This variable sets default format used for binary packages. Possible values
+are tar and rpm or both.
+.TP
+\fBPORTAGE_BUNZIP2_COMMAND\fR = \fI[bunzip2 command string]\fR
+This variable should contain a command that is suitable for portage to call
+for bunzip2 extraction operations.
+.TP
+\fBPORTAGE_BZIP2_COMMAND\fR = \fI[bzip2 command string]\fR
+This variable should contain a command that is suitable for portage to call
+for bzip2 compression operations. \fBPORTAGE_BZIP2_COMMAND\fR will also be
+called for extraction operation, with -d appended, unless the
+\fBPORTAGE_BUNZIP2_COMMAND\fR variable is set.
+.TP
+\fBPORTAGE_CHECKSUM_FILTER\fR = \fI[space delimited list of hash names]\fR
+This variable may be used to filter the hash functions that are used to
+verify integrity of files. Hash function names are case\-insensitive, and
+the \fI*\fR and \fI\-*\fR wildcard tokens are supported.
+.br
+Defaults to the value of *.
+.br
+.I Examples:
+.nf
+# Use all available hash functions
+PORTAGE_CHECKSUM_FILTER="*"
+# Use any function except whirlpool
+PORTAGE_CHECKSUM_FILTER="* \-whirlpool"
+# Only use sha256
+PORTAGE_CHECKSUM_FILTER="\-* sha256"
+.fi
+.TP