vrrp_track_process works with "hidepid=2,gid=procadmins" only after a reboot?

[mathieumd]

Describe the bug
When hidepid=2 and gid=procadmins are enabled on /proc (see Configuring procfs), the vrrp_track_process[1] was working only at keepalived process starts, no more after. But after I rebooted the machine, it finally works well.

[1] By the way, it looks like the website version of the man page is obsolete!

To Reproduce

1. Add hidepid=2,gid=procadmins to your /proc line in /etc/fstab, then reboot;
2. Install and configure Keepalived with a vrrp_track_process;
3. Stop the process tracked: nothing happens;
4. Reboot;
5. Stop the process tracked: VIP switching is happening has expected;

Keepalived version

Keepalived v2.2.8 (04/04,2023), git commit v2.2.7-154-g292b299e+

Copyright(C) 2001-2023 Alexandre Cassen, <acassen@gmail.com>

Built with kernel headers for Linux 6.8.0
Running on Linux 6.8.0-90-generic #91-Ubuntu SMP PREEMPT_DYNAMIC Tue Nov 18 14:14:30 UTC 2025
Distro: Ubuntu 24.04.3 LTS

configure options: --build=x86_64-linux-gnu --prefix=/usr --includedir=${prefix}/include --mandir=${prefix}/share/man --infodir=${prefix}/share/info --sysconfdir=/etc --localstatedir=/var --disable-option-checking --disable-silent-rules --libdir=${prefix}/lib/x86_64-linux-gnu --runstatedir=/run --disable-maintainer-mode --disable-dependency-tracking --enable-snmp --enable-sha1 --enable-snmp-rfcv2 --enable-snmp-rfcv3 --enable-dbus --enable-json --enable-bfd --enable-regex --with-init=systemd build_alias=x86_64-linux-gnu CFLAGS=-g -O2 -fno-omit-frame-pointer -mno-omit-leaf-frame-pointer  -flto=auto -ffat-lto-objects -fstack-protector-strong -fstack-clash-protection -Wformat -Werror=format-security -fcf-protection -fdebug-prefix-map=/build/keepalived-F53vvG/keepalived-2.2.8=/usr/src/keepalived-1:2.2.8-1build2 LDFLAGS=-Wl,-Bsymbolic-functions -flto=auto -ffat-lto-objects -Wl,-z,relro CPPFLAGS=-Wdate-time -D_FORTIFY_SOURCE=3

Config options:  NFTABLES LVS REGEX VRRP VRRP_AUTH VRRP_VMAC JSON BFD OLD_CHKSUM_COMPAT SNMP_V3_FOR_V2 SNMP_VRRP SNMP_CHECKER SNMP_RFCV2 SNMP_RFCV3 DBUS INIT=systemd SYSTEMD_NOTIFY

System options:  VSYSLOG MEMFD_CREATE IPV6_MULTICAST_ALL IPV4_DEVCONF LIBNL3 RTA_ENCAP RTA_EXPIRES RTA_NEWDST RTA_PREF FRA_SUPPRESS_PREFIXLEN FRA_SUPPRESS_IFGROUP FRA_TUN_ID RTAX_CC_ALGO RTAX_QUICKACK RTEXT_FILTER_SKIP_STATS FRA_L3MDEV FRA_UID_RANGE RTAX_FASTOPEN_NO_COOKIE RTA_VIA FRA_PROTOCOL FRA_IP_PROTO FRA_SPORT_RANGE FRA_DPORT_RANGE RTA_TTL_PROPAGATE IFA_FLAGS LWTUNNEL_ENCAP_MPLS LWTUNNEL_ENCAP_ILA NET_LINUX_IF_H_COLLISION LIBIPVS_NETLINK IPVS_DEST_ATTR_ADDR_FAMILY IPVS_SYNCD_ATTRIBUTES IPVS_64BIT_STATS IPVS_TUN_TYPE IPVS_TUN_CSUM IPVS_TUN_GRE VRRP_IPVLAN IFLA_LINK_NETNSID GLOB_BRACE GLOB_ALTDIRFUNC INET6_ADDR_GEN_MODE VRF SO_MARK

Distro (please complete the following information):

• Name:Ubuntu
• Version: 24.04.3 LTS
• Architecture: x86_64

Details of any containerisation or hosted service (e.g. AWS)
Proxmox VM

Configuration file:

global_defs {
  process_names
  router_id rp02

  notification_email {
    mathieu@example.com
  }
  notification_email_from root+keepalived@example.com
  smtp_server localhost
  smtp_alert
}

vrrp_track_process track_nginx {
  process nginx
  delay 1
}

vrrp_instance RP_VI1 {
  state BACKUP
  priority 90

  virtual_router_id 1
  interface eth0
  advert_int 1
  authentication {
    auth_type PASS
    auth_pass XX
  }
  virtual_ipaddress {
    10.1.1.14
  }
  track_process {
    track_nginx
  }
}

vrrp_instance RP_VI2 {
  state MASTER
  priority 20

  virtual_router_id 2
  interface eth0
  advert_int 1
  authentication {
    auth_type PASS
    auth_pass XX
  }
  virtual_ipaddress {
    10.1.1.15
  }
  track_process {
    track_nginx
  }
}

System Log entries

-- Boot 67cf02fdc4564be99d1475ffd5a94190 --
déc. 12 13:06:47 rp02 systemd[1]: Starting keepalived.service - Keepalive Daemon (LVS and VRRP)...
déc. 12 13:06:47 rp02 Keepalived[853]: Starting Keepalived v2.2.8 (04/04,2023), git commit v2.2.7-154-g292b299e+
déc. 12 13:06:47 rp02 Keepalived[853]: Running on Linux 6.8.0-90-generic #91-Ubuntu SMP PREEMPT_DYNAMIC Tue Nov 18 14:14:30 UTC 2025 (built for Linux 6.8.0)
déc. 12 13:06:47 rp02 Keepalived[853]: Command line: '/usr/sbin/keepalived' '--dont-fork'
déc. 12 13:06:47 rp02 Keepalived[853]: Configuration file /etc/keepalived/keepalived.conf
déc. 12 13:06:47 rp02 Keepalived[853]: NOTICE: setting config option max_auto_priority should result in better keepalived performance
déc. 12 13:06:47 rp02 Keepalived[853]: Starting VRRP child process, pid=858
déc. 12 13:06:47 rp02 Keepalived_vrrp[858]: (RP_VI1) entering FAULT state (tracked process track_nginx quorum not achieved)
déc. 12 13:06:47 rp02 Keepalived_vrrp[858]: (RP_VI2) entering FAULT state (tracked process track_nginx quorum not achieved)
déc. 12 13:06:47 rp02 Keepalived_vrrp[858]: (RP_VI1) entering FAULT state
déc. 12 13:06:47 rp02 Keepalived_vrrp[858]: (RP_VI2) entering FAULT state
déc. 12 13:06:47 rp02 Keepalived[853]: Startup complete
déc. 12 13:06:47 rp02 Keepalived_vrrp[858]: smtp fd 13 returned write error
déc. 12 13:06:47 rp02 Keepalived_vrrp[858]: smtp fd 14 returned write error
déc. 12 13:06:47 rp02 Keepalived_vrrp[858]: Quorum gained for tracked process track_nginx
déc. 12 13:06:47 rp02 Keepalived_vrrp[858]: (RP_VI1) Entering BACKUP STATE
déc. 12 13:06:47 rp02 Keepalived_vrrp[858]: (RP_VI2) Entering BACKUP STATE
déc. 12 13:06:47 rp02 Keepalived_vrrp[858]: smtp fd 13 returned write error
déc. 12 13:06:47 rp02 Keepalived_vrrp[858]: smtp fd 14 returned write error
déc. 12 13:06:48 rp02 systemd[1]: Started keepalived.service - Keepalive Daemon (LVS and VRRP).
déc. 12 13:06:48 rp02 Keepalived_vrrp[858]: (RP_VI2) received lower priority (10) advert from 10.0.0.1 - discarding
déc. 12 13:06:48 rp02 Keepalived_vrrp[858]: (RP_VI2) received lower priority (10) advert from 10.0.0.1 - discarding
déc. 12 13:06:49 rp02 Keepalived_vrrp[858]: (RP_VI2) received lower priority (10) advert from 10.0.0.1 - discarding
déc. 12 13:06:49 rp02 Keepalived_vrrp[858]: (RP_VI2) received lower priority (10) advert from 10.0.0.1 - discarding
déc. 12 13:06:50 rp02 Keepalived_vrrp[858]: (RP_VI2) received lower priority (10) advert from 10.0.0.1 - discarding
déc. 12 13:06:50 rp02 Keepalived_vrrp[858]: (RP_VI2) received lower priority (10) advert from 10.0.0.1 - discarding
déc. 12 13:06:51 rp02 Keepalived_vrrp[858]: (RP_VI2) received lower priority (10) advert from 10.0.0.1 - discarding
déc. 12 13:06:51 rp02 Keepalived_vrrp[858]: (RP_VI2) received lower priority (10) advert from 10.0.0.1 - discarding
déc. 12 13:06:51 rp02 Keepalived_vrrp[858]: (RP_VI2) Entering MASTER STATE
déc. 12 13:07:15 rp02 Keepalived_vrrp[858]: Quorum lost for tracked process track_nginx
déc. 12 13:07:15 rp02 Keepalived_vrrp[858]: (RP_VI1) Entering FAULT STATE
déc. 12 13:07:15 rp02 Keepalived_vrrp[858]: (RP_VI2) Entering FAULT STATE
déc. 12 13:07:35 rp02 Keepalived_vrrp[858]: Quorum gained for tracked process track_nginx
déc. 12 13:07:35 rp02 Keepalived_vrrp[858]: (RP_VI1) Entering BACKUP STATE
déc. 12 13:07:35 rp02 Keepalived_vrrp[858]: (RP_VI2) Entering BACKUP STATE
déc. 12 13:07:36 rp02 Keepalived_vrrp[858]: (RP_VI2) received lower priority (10) advert from 10.0.0.1 - discarding
déc. 12 13:07:37 rp02 Keepalived_vrrp[858]: (RP_VI2) received lower priority (10) advert from 10.0.0.1 - discarding
déc. 12 13:07:38 rp02 Keepalived_vrrp[858]: (RP_VI2) received lower priority (10) advert from 10.0.0.1 - discarding
déc. 12 13:07:39 rp02 Keepalived_vrrp[858]: (RP_VI2) received lower priority (10) advert from 10.0.0.1 - discarding
déc. 12 13:07:39 rp02 Keepalived_vrrp[858]: (RP_VI2) Entering MASTER STATE
déc. 12 13:08:13 rp02 Keepalived_vrrp[858]: (RP_VI1) Entering MASTER STATE
déc. 12 13:08:44 rp02 Keepalived_vrrp[858]: (RP_VI1) Master received advert from 10.0.0.1 with higher priority 100, ours 90
déc. 12 13:08:44 rp02 Keepalived_vrrp[858]: (RP_VI1) Entering BACKUP STATE
déc. 12 13:09:03 rp02 Keepalived_vrrp[858]: (RP_VI1) Entering MASTER STATE
déc. 12 13:09:14 rp02 Keepalived_vrrp[858]: (RP_VI1) Master received advert from 10.0.0.1 with higher priority 100, ours 90
déc. 12 13:09:14 rp02 Keepalived_vrrp[858]: (RP_VI1) Entering BACKUP STATE