setfont [-O font+umap.orig] [-o font.orig] [-om cmap.orig] [-ou umap.orig] [-N] [font.new ...] [-m cmap] [-u umap] [-C console] [-hH] [-v] [-V]
The setfont command reads a font from the file font.new and loads it into the EGA/VGA character generator, and optionally outputs the previous font. It can also load various mapping tables and output the previous versions.
If no args are given (or only the option -N for some number N), then a default (8xN) font is loaded (see below). One may give several small fonts, all containing a Unicode table, and setfont will combine them and load the union. Typical use:
Note: if a font has more than 256 glyphs, only 8 out of 16 colors can be used simultaneously. It can make console perception worse (loss of intensity and even some colors).
The standard Linux font format is the PSF font. It has a header describing font properties like character size, followed by the glyph bitmaps, optionally followed by a Unicode mapping table giving the Unicode value for each glyph. Several other (obsolete) font formats are recognized. If the input file has code page format (probably with suffix .cp), containing three fonts with sizes e.g. 8x8, 8x14 and 8x16, then one of the options -8 or -14 or -16 must be used to select one. Raw font files are binary files of size 256*N bytes, containing bit images for each of 256 characters, one byte per scan line, and N bytes per character (0 < N <= 32). Most fonts have a width of 8 bits, but with the framebuffer device (fb) other widths can be used.
The program setfont has no built-in knowledge of VGA video modes, but just asks the kernel to load the character ROM of the video card with certain bitmaps. However, since Linux 1.3.1 the kernel knows enough about EGA/VGA video modes to select a different line distance. The default character height will be the number N inferred from the font or specified by option. However, the user can specify a different character height H using the -h option.
Several mappings are involved in the path from user program output to console display. If the console is in utf8 mode (see unicode_start(1)) then the kernel expects that user program output is coded as UTF-8 (see utf-8(7)), and converts that to Unicode (ucs2). Otherwise, a translation table is used from the 8-bit program output to 16-bit Unicode values. Such a translation table is called a Unicode console map. There are four of them: three built into the kernel, the fourth settable using the -m option of setfont. An escape sequence chooses between these four tables; after loading a cmap, setfont will output the escape sequence Esc ( K that makes it the active translation.
Suitable arguments for the -m option are for example 8859-1, 8859-2, ..., 8859-15, cp437, ..., cp1250.
Given the Unicode value of the symbol to be displayed, the kernel finds the right glyph in the font using the Unicode mapping info of the font and displays it.
Old fonts do not have Unicode mapping info, and in order to handle them there are direct-to-font maps (also loaded using -m) that give a correspondence between user bytes and font positions. The most common correspondence is the one given in the file trivial (where user byte values are used directly as font positions). Other correspondences are sometimes preferable since the PC video hardware expects line drawing characters in certain font positions.
Giving a -m none argument inhibits the loading and activation of a mapping table. The previous console map can be saved to a file using the -om file option. These options of setfont render mapscrn(8) obsolete. (However, it may be useful to read that man page.)
The correspondence between the glyphs in the font and Unicode values is described by a Unicode mapping table. Many fonts have a Unicode mapping table included in the font file, and an explicit table can be indicated using the -u option. The program setfont will load such a Unicode mapping table, unless a -u none argument is given. The previous Unicode mapping table will be saved as part of the saved font file when the -O option is used. It can be saved to a separate file using the -ou file option. These options of setfont render loadunimap(8) obsolete.
The Unicode mapping table should assign some glyph to the `missing character' value U+fffd, otherwise missing characters are not translated, giving a usually very confusing result.
Usually no mapping table is needed, and a Unicode mapping table is already contained in the font (sometimes this is indicated by the .psfu extension), so that most users need not worry about the precise meaning and functioning of these mapping tables.
One may add a Unicode mapping table to a psf font using psfaddtable(1).
PC video hardware allows one to use the "intensity" bit either to indicate brightness, or to address 512 (instead of 256) glyphs in the font. So, if the font has more than 256 glyphs, the console will be reduced to 8 (instead of 16) colors.
/usr/share/consolefonts is the default font directory. /usr/share/unimaps is the default directory for Unicode maps. /usr/share/consoletrans is the default directory for screen mappings. The default font is a file default (or default8xN if the -N option was given for some number N) perhaps with suitable extension (like .psf).
psfaddtable(1), unicode_start(1), loadunimap(8), utf-8(7), mapscrn(8)