xdm.options(5)

💖 xdm.options — configuration options for the X display manager 💖

okay bestie, welcome to xdm.options(5), aka the little file that tells the X display manager how to act. it's filed under File Formats Manual, and it's genuinely so much simpler than it looks. let's get into it 🫶

✨ NAME ✨

xdm.options — configuration options for the X display manager

🌸 DESCRIPTION 🌸

so, /etc/X11/xdm/xdm.options holds a set of flags that decide some of the behavior of the X display manager, xdm(1x). key word: some. most of xdm's behavior gets customized through other files, so if this page doesn't describe the thing you want to change, go read the xdm manual page instead. this one isn't gonna cover it, no cap.

/etc/X11/xdm/xdm.options can contain comments, and they start with a hash mark (#) and run until the next newline — literally exactly like comments in shell scripts. the rest of the file is just options, expressed as words separated by hyphens, with only one option per line.

enabling an option is the easiest thing ever: you just put it in the file. disabling it? prefix the option name with no-. that's it, that's the whole mechanic. 💅

available options are:

• ignore-nologin — normally, if the nologin(5) file exists, its contents get displayed using xmessage(1x) (if xmessage is available), and then the user gets sent back to the xdm login screen after xmessage is dismissed, instead of starting the X session. if this option is enabled, xdm starts a session as usual (after xmessage is dismissed, if xmessage is available and the nologin file exists). this behavior is disabled by default: nologin is heeded, not ignored. periodt.
• restart-on-upgrade — ⚠️ enable this one with caution on "production" machines, fr fr. it causes the daemon to be stopped and restarted on upgrade, even if the process has children (which means it's managing X sessions, bestie 😭). typically, when a package containing a daemon is being installed or upgraded, its maintainer scripts stop a running daemon process before installing the new binary, and restart it after the new binary is installed. stopping xdm causes immediate termination of any sessions it manages, and in some situations that could be a very unwelcome surprise (for instance, for remote xdm users who had absolutely no idea the administrator was doing system maintenance 🙈). on the other hand, for machines that stay up for long periods of time, leaving the old daemon running can be a bad idea if the new version has, like, a fix for a security vulnerability (overwriting xdm's executable on the file system has no effect on the copy of xdm in memory — it's giving ghost of daemons past 💀). the xdm package's pre-removal script checks to see if the xdm process has any children; if it does, it's possible that someone's session would be killed by stopping xdm, so a warning is issued and you get an opportunity to abort the upgrade of xdm. furthermore, restarting xdm on upgrade can be surprising, because a locally-managed X server can change the active VT even while other packages are continuing to upgrade. and if, by intent or accident, the X server does not honor the key sequence to switch VTs back to a virtual console, that can be undesirable. this behavior is disabled by default: xdm will be not be stopped or started during an upgrade of its package; the administrator will have to do so by hand (with invoke-rc.d xdm restart or by rebooting the system) before the newly installed xdm binary is used. so like... your call, but be smart about it 🧚
• start-on-install — enable this option with caution too! it causes the xdm daemon to be started immediately after the package is installed. see the above entry about restart-on-upgrade for other caveats regarding the consequences of starting the xdm daemon during package management. this behavior is disabled by default: xdm will not be started when it is installed. and heads up — changing this setting can affect future installs if the package is removed, but not purged (purging removes conffiles, including xdm.options). 👑
• use-sessreg — this option causes the /etc/X11/xdm/Xreset script to call the sessreg(1x) program to register X sessions managed by xdm in the utmp(5) and wtmp(5) files. if it is disabled, the utmp and wtmp files will have no record of xdm sessions. this behavior is enabled by default; sessreg will be used. ✨

bestie, if you're coming from older versions of the Debian system, please note that the run-xconsole option has been removed. the shell script named /etc/X11/xdm/Xreset can be edited to disable or modify the running of xconsole on the xdm greeter screen; see xdm(1x) for more information. it's not gone, it just moved 💜

🌈 AUTHORS 🌈

Stephen Early, Mark Eichin, and Branden Robinson customized xdm's startup and reset scripts and package maintainer scripts to implement the functionality described above. this manual page was written by Branden Robinson. absolute icons, all of them 👑

🦋 SEE ALSO 🦋

• sessreg(1x)
• xmessage(1x)
• xdm(1x)
• nologin(5)
• utmp(5)
• wtmp(5)

and that's the whole page, bestie, you ate it 🍓 this one's from the Debian Project, dated 2004-10-31 — old but iconic, and honestly still the blueprint. go forth and configure responsibly 💖✨🎀