After installing on Power Mac G5, gdm was not starting. Short info: G5, gentoo from stage3, profile default/linux/powerpc/ppc64/17.0/64bit-userland/desktop/gnome/systemd (stable). Lots of uninformative messages in journal: Feb 27 23:59:54 PPC gdm[13827]: GdmDisplay: Creating greeter for (null) (null) Feb 27 23:59:55 PPC systemd[1]: Started /run/user/114 mount wrapper. Feb 27 23:59:54 PPC gdm[13827]: GdmLaunchEnvironment: Starting... Feb 27 23:59:54 PPC gdm[13827]: GdmLaunchEnvironment: Setting up run time dir /run/gdm/greeter Feb 27 23:59:54 PPC gdm[13827]: GdmSession: Creating D-Bus server for worker for session Feb 27 23:59:54 PPC gdm[13827]: GdmSession: D-Bus server for workers listening on unix:abstract=/tmp/dbus-RLouJ8N0 Feb 27 23:59:54 PPC gdm[13827]: GdmSession: Creating D-Bus server for greeters and such Feb 27 23:59:54 PPC gdm[13827]: GdmSession: D-Bus server for greeters listening on unix:abstract=/tmp/dbus-OD2lscfe Feb 27 23:59:54 PPC gdm[13827]: GdmSession: Setting display device: (null) Feb 27 23:59:54 PPC gdm[13827]: GdmSession: starting conversation gdm-launch-environment Feb 27 23:59:54 PPC gdm[13827]: GdmSessionWorkerJob: Starting worker... Feb 27 23:59:54 PPC gdm[13827]: GdmSessionWorkerJob: Running session_worker_job process: gdm-session-worker [pam/gdm-launch-environment] /usr/libexec/gdm-session-worker Feb 27 23:59:54 PPC gdm[13827]: GdmSessionWorkerJob: : SessionWorkerJob on pid 14048 Feb 27 23:59:55 PPC systemd[1]: Starting User Manager for UID 114... Feb 27 23:59:54 PPC gdm[13827]: GdmLocalDisplayFactory: display status changed: 1 Feb 27 23:59:54 PPC gdm[13827]: GdmDisplay: Disposing display Feb 27 23:59:54 PPC gdm[13827]: GdmCommon: sending signal 15 to process -14040 Feb 27 23:59:54 PPC gdm[13827]: Child process -14040 was already dead. Feb 27 23:59:54 PPC gdm[13827]: GdmSession: Closing session Feb 27 23:59:54 PPC gdm[13827]: GdmSession: Stopping all conversations Feb 27 23:59:54 PPC gdm[13827]: GdmSessionWorkerJob: Stopping job pid:14022 Feb 27 23:59:54 PPC gdm[13827]: GdmCommon: sending signal 15 to process 14022 Feb 27 23:59:54 PPC gdm[13827]: Child process 14022 was already dead. Feb 27 23:59:54 PPC gdm[13827]: Unable to kill session worker process Feb 27 23:59:54 PPC gdm[13827]: GdmSessionWorkerJob: Waiting on process 14022 Feb 27 23:59:54 PPC gdm[13827]: GdmCommon: process (pid:14022) done (reaped earlier:1) Feb 27 23:59:54 PPC gdm[13827]: GdmSessionWorkerJob: SessionWorkerJob died Feb 27 23:59:54 PPC gdm[13827]: GdmSession: Disposing session Feb 27 23:59:54 PPC gdm[13827]: GdmSession: Closing session Feb 27 23:59:54 PPC gdm[13827]: GdmSession: Stopping all conversations Feb 27 23:59:54 PPC gdm[13827]: GdmDisplay: Finalizing display: /org/gnome/DisplayManager/Displays/4399303760 Feb 27 23:59:54 PPC gdm[13827]: GdmDisplay: finish display Feb 27 23:59:54 PPC gdm-launch-environment][14048]: Enabling debugging Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: connecting to address: unix:abstract=/tmp/dbus-RLouJ8N0 Feb 27 23:59:54 PPC gdm[13827]: GdmDBusServer: new connection 0x3fff7c007190 Feb 27 23:59:54 PPC gdm[13827]: GdmSession: Handling new connection from worker Feb 27 23:59:54 PPC gdm[13827]: GdmSession: Authenticating new connection Feb 27 23:59:54 PPC gdm-launch-environment][14048]: AccountsService: Failed to identify the current session: No data available Feb 27 23:59:54 PPC gdm-launch-environment][14048]: AccountsService: ActUserManager: seat unloaded, so trying to set loaded property Feb 27 23:59:54 PPC gdm-launch-environment][14048]: AccountsService: ActUserManager: Seat wouldn't load, so giving up on it and setting loaded property Feb 27 23:59:54 PPC gdm-launch-environment][14048]: AccountsService: ActUserManager: already loaded, so not setting loaded property Feb 27 23:59:54 PPC gdm[13827]: GdmSession: worker connection is 0x3fff7c007190 Feb 27 23:59:54 PPC gdm[13827]: GdmSession: Emitting conversation-started signal Feb 27 23:59:54 PPC gdm[13827]: GdmSession: Beginning initialization Feb 27 23:59:54 PPC gdm[13827]: GdmSession: Conversation started Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: attempting to change state to SETUP_COMPLETE Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: initializing PAM; service=gdm-launch-environment username=gdm seat=seat0 Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: Set PAM environment variable: 'XDG_SEAT=seat0' Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: Set PAM environment variable: 'XDG_SESSION_CLASS=greeter' Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: state SETUP_COMPLETE Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: attempting to change state to AUTHENTICATED Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: authenticating user gdm Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: state AUTHENTICATED Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: attempting to change state to AUTHORIZED Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: determining if authenticated user (password required:0) is authorized to session Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: state AUTHORIZED Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: attempting to change state to ACCREDITED Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: Set PAM environment variable: 'LOGNAME=gdm' Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: Set PAM environment variable: 'USER=gdm' Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: Set PAM environment variable: 'USERNAME=gdm' Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: Set PAM environment variable: 'HOME=/var/lib/gdm' Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: Set PAM environment variable: 'SHELL=/sbin/nologin' Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: Set PAM environment variable: 'PATH=/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin' Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: state ACCREDITED Feb 27 23:59:54 PPC gdm[13827]: GdmSession: type (null), program? yes, seat seat0 Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: session display mode set to new-vt Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: Set PAM environment variable: 'XDG_SESSION_TYPE=x11' Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: attempting to change state to ACCOUNT_DETAILS_SAVED Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: user gdm, not fully loaded yet, will save account details later Feb 27 23:59:54 PPC gdm-launch-environment][14048]: AccountsService: ActUserManager: trying to track new user with username gdm Feb 27 23:59:54 PPC gdm-launch-environment][14048]: AccountsService: ActUserManager: finding user 'gdm' state 1 Feb 27 23:59:54 PPC gdm-launch-environment][14048]: AccountsService: ActUserManager: finding user 'gdm' state 2 Feb 27 23:59:54 PPC gdm-launch-environment][14048]: AccountsService: ActUserManager: Looking for user 'gdm' in accounts service Feb 27 23:59:54 PPC gdm-launch-environment][14048]: AccountsService: ActUserManager: Found object path of user 'gdm': /org/freedesktop/Accounts/User114 Feb 27 23:59:54 PPC gdm-launch-environment][14048]: AccountsService: ActUserManager: finding user 'gdm' state 3 Feb 27 23:59:54 PPC gdm-launch-environment][14048]: AccountsService: ActUserManager: user 'gdm' fetched Feb 27 23:59:54 PPC gdm-launch-environment][14048]: AccountsService: ActUserManager: user gdm is now loaded Feb 27 23:59:54 PPC gdm-launch-environment][14048]: AccountsService: ActUserManager: user gdm was not yet known, adding it Feb 27 23:59:54 PPC gdm-launch-environment][14048]: AccountsService: ActUserManager: tracking user 'gdm' Feb 27 23:59:54 PPC gdm-launch-environment][14048]: AccountsService: ActUserManager: not yet loaded, so not emitting user-added signal Feb 27 23:59:54 PPC gdm-launch-environment][14048]: AccountsService: ActUserManager: no pending users, trying to set loaded property Feb 27 23:59:54 PPC gdm-launch-environment][14048]: AccountsService: ActUserManager: already loaded, so not setting loaded property Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionSettings: saved session is Feb 27 23:59:55 PPC systemd-logind[3920]: New session c441 of user gdm. Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionSettings: saved language is Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: saving account details for user gdm Feb 27 23:59:54 PPC gdm-launch-environment][14048]: AccountsService: ActUserManager: finished handling request for user 'gdm' Feb 27 23:59:54 PPC gdm-launch-environment][14048]: AccountsService: ActUserManager: unrefing manager owned by fetch user request Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: attempting to change state to SESSION_OPENED Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: Set PAM environment variable: 'XDG_VTNR=7' Feb 27 23:59:54 PPC gdm-launch-environment][14048]: pam_systemd(gdm-launch-environment:session): Unknown parameter 'kill-session-processes=1', ignoring Feb 27 23:59:54 PPC systemd[14053]: pam_unix(systemd-user:session): session opened for user gdm by (uid=0) Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: state SESSION_OPENED Feb 27 23:59:54 PPC gdm[13827]: GdmSession: Emitting 'session-opened' signal Feb 27 23:59:54 PPC gdm[13827]: GdmDisplay: Greeter session opened Feb 27 23:59:54 PPC gdm[13827]: GdmDisplay: session id: c440 Feb 27 23:59:54 PPC gdm[13827]: GdmSession: Stopping all conversations except for gdm-launch-environment Feb 27 23:59:54 PPC gdm[13827]: GdmSession: type (null), program? yes, seat seat0 Feb 27 23:59:54 PPC gdm[13827]: GdmSession: type (null), program? yes, seat seat0 Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: Set PAM environment variable: 'GDM_LANG=en_US.utf8' Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: Set PAM environment variable: 'DCONF_PROFILE=gdm' Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: Set PAM environment variable: 'HOME=/var/lib/gdm' Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: Set PAM environment variable: 'GDM_SEAT_ID=seat0' Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: Set PAM environment variable: 'RUNNING_UNDER_GDM=true' Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: Set PAM environment variable: 'GVFS_DISABLE_FUSE=1' Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: Set PAM environment variable: 'XDG_CURRENT_DESKTOP=GNOME-Greeter:GNOME' Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: Set PAM environment variable: 'LANG=en_US.utf8' Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: Set PAM environment variable: 'LOGNAME=gdm' Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: Set PAM environment variable: 'GVFS_REMOTE_VOLUME_MONITOR_IGNORE=1' Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: Set PAM environment variable: 'GIO_USE_VFS=local' Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: Set PAM environment variable: 'GDM_VERSION=3.26.2.1' Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: Set PAM environment variable: 'GNOME_SHELL_SESSION_MODE=gdm' Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: Set PAM environment variable: 'USERNAME=gdm' Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: Set PAM environment variable: 'PWD=/var/lib/gdm' Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: Set PAM environment variable: 'USER=gdm' Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: Set PAM environment variable: 'PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin' Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: Set PAM environment variable: 'SHELL=/sbin/nologin' Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: Set PAM environment variable: 'XDG_DATA_DIRS=/usr/share/gdm/greeter:/usr/local/share/:/usr/share/' Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: start program: /usr/libexec/gdm-x-session "gnome-session --autostart /usr/share/gdm/greeter/autostart --debug" Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: attempting to change state to SESSION_STARTED Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: opening session for program '/usr/libexec/gdm-x-session' Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: jumping to VT 7 Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: first setting graphics mode to prevent flicker Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: VT mode did not need to be fixed Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: session opened creating reply... Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSessionWorker: state SESSION_STARTED Feb 27 23:59:54 PPC gdm-launch-environment][14048]: GdmSession worker: watching pid 14058 Feb 27 23:59:54 PPC gdm[13827]: GdmSession: Emitting 'session-started' signal with pid '14058' Feb 27 23:59:54 PPC gdm[13827]: GdmDisplay: Greeter started Feb 27 23:59:54 PPC gdm-x-session[14058]: Enabling debugging Feb 27 23:59:54 PPC gdm-x-session[14058]: Preparing auth file for X server Feb 27 23:59:54 PPC gdm-x-session[14058]: Running X server Feb 27 23:59:55 PPC gdm-x-session[14058]: X server did not write display string Feb 27 23:59:55 PPC gdm-launch-environment][14048]: GdmSessionWorker: child (pid:14058) done (status:70) Feb 27 23:59:55 PPC gdm-launch-environment][14048]: GdmSessionWorker: uninitializing PAM Feb 27 23:59:55 PPC gdm-launch-environment][14048]: GdmSessionWorker: jumping to VT 1 Feb 27 23:59:55 PPC gdm-launch-environment][14048]: GdmSessionWorker: state NONE Feb 27 23:59:55 PPC gdm[13827]: GdmSession: Emitting 'session-exited' signal with exit code '70' Feb 27 23:59:55 PPC gdm[13827]: GdmSession: stopping conversation gdm-launch-environment Feb 27 23:59:55 PPC gdm[13827]: GdmSessionWorkerJob: Stopping job pid:14048 Feb 27 23:59:55 PPC gdm[13827]: GdmCommon: sending signal 15 to process 14048 Feb 27 23:59:55 PPC gdm[13827]: GdmDisplay: Greeter exited: 70 ...Well, long story short, emerging gdm did not produce /var/lib/gdm/.local/share/xorg folder, which blocked starting of gdm. Mkdir, chown - all works. Please, fix it for other unlucky users!
Please retry with an updated system. Current ebuilds ensure /var/lib/gdm has the owner and permissions needed to create those files when needed