login-banner 1 user commands nosh login-bannerchain-load utility for printing login banners login-banner --utmp-filename filename template-filename next-prog login-banner is a chain-loading utility that prints a system banner to its standard output, and then (if successful) chain loads to next-prog with the execvp3 library function. Normally, the next-prog will be (or will eventually chain-load) login1, which prints the login prompt(s) after the banner. next-prog may contain its own command line options, which login-banner will ignore. login-banner makes no alteration to process state. With various pieces of system information to hand it displays the contents of template-filename to its standard output. The file is displayed as-is, with the exception that a backslash character begins a two-character escape sequence. The following escape sequences are defined: \\ A single backslash. \d The current date in the local timezone of the process. \h The "hostname", by default the dynamic hostname obtained from the gethostname2 library function. See set-dynamic-hostname1 for how this is set. login-banner allows the value held by the kernel to be overridden by the value of a HOSTNAME environment variable (the same convention as machineenv1). \L The "location" name, from the /etc/machine-info file, if available. This defaults to an empty string. \l The "line", i.e. the pathname of the controlling TTY name relative to /dev, from the ttyname3 library function (applied to standard input). login-banner allows the value held by the kernel to be overridden by the value of a TTY environment variable (the same convention as vc-get-terminal1 or pty-allocate1, or an equivalent getty1 program that sets that variable, and usually the case in TTY login services which chain to login-banner via these). \m The "machine" name, from the uname2 library function. On FreeBSD, the C library allows the value held by the kernel to be overridden by the value of a UNAME_m environment variable. \N The "pretty" "node" name, from the /etc/machine-info file, if available. This defaults to the same as \n. \n The "node" name, from the uname2 library function. See set-dynamic-hostname1 for how this is set and why in practice it is identical to, and redundant with, the "hostname" from the expansion of \h. Despite the claim in its documentation, on FreeBSD the C library does not allow the value held by the kernel to be overridden by the value of a UNAME_n environment variable. \O The "DNS domain name", derived from the "hostname" by taking it to be (the human-readable form of) a DNS domain name and stripping its first "label". login-banner allows the value held by the kernel to be overridden by the value of a LOCALDOMAIN environment variable (a common DNS client library convention). See set-dynamic-hostname1 for the bewildering and (self-)contradictory range of ways in which various programs derive the DNS domain name from the hostname. \o The "NIS domain" name, from the getdomainname2 library function. See set-dynamic-hostname1 for how this is set. login-banner allows the value held by the kernel to be overridden by the value of a DOMAINNAME environment variable (the same convention as machineenv1). \p The "deployment" name, from the /etc/machine-info file, if available. This defaults to an empty string. \r The "release" name, from the uname2 library function. On FreeBSD, the C library allows the value held by the kernel to be overridden by the value of a UNAME_r environment variable. \S The "pretty" "system" name, from the /etc/os-release file, if available. This defaults to the same as \s. \s The "system" name, from the uname2 library function. On FreeBSD, the C library allows the value held by the kernel to be overridden by the value of a UNAME_s environment variable. \t The current time in the local timezone of the process. \U The number of users logged on, followed by a space and the string "users" (or "user" if the number is exactly one). See \u for how this information is obtained. \u The number of users logged on. login-banner derives information about the number of users logged on from the utmp file. The location of the utmp file is derived at compile time from a system header when the utility is built from source. To override it at runtime, use the --utmp-filename option. \v The "version" name, from the uname2 library function. On FreeBSD, the C library allows the value held by the kernel to be overridden by the value of a UNAME_v environment variable. \z The local timezone of the process. All other escape sequences are reserved for future expansion. The program requires permission to read utmp and the template file. The functionality is a rough superset of that for "issue" files provided by other tools that implement the old and superseded "getty" tool: Wietse Venema's agetty1 only understands \d, \l, \m, \n, \o, \r, \S, \s, \t, \U, \u, and \v in the same way. It has \4, \6, \b, and \e which are not in login-banner. Felix von Leiner's fgetty1, Florian La Roche's mingetty1, and Nikola Vladov's ngetty1 only understand \d, \l, \m, \n, \o, \r, \s, \t, \U, \u, and \v. Gert Doering's mgetty1 only understands \m and \s in the same way. It has \d, \l, \r, \t, \u, and \v but in upper case rather than lower case. And it has \C, \I, \N, \P, \S, and \Y which are not in login-banner, being aliases for other escape sequences, specific to remote serial terminals and dial-up, or U.S.-specific old style date+time formats. login-banner doesn't really care if its standard output is not a virtual console, or even a terminal or a character device at all. It can be used to display login banners to arbitrary destinations, even to sockets and to files. (Although one must ensure that it always inherits a TTY environment variable in such cases, so that the \l escape sequence expands to the appropriate thing, and not to the name of some irrelevant controlling terminal.) The following nosh1 script is (roughly) equivalent to what in.telnetd1 does, except that it doesn't handle the TELNET protocol negotiation or the various debugging options. #!/bin/nosh pty-allocate pty-run setsid open-controlling-terminal login-banner /etc/issue.net login This is the sh1 equivalent: #!/bin/sh -e exec \ pty-allocate \ pty-run \ open-controlling-terminal \ login-banner /etc/issue.net \ login Jonathan de Boyne Pollard