** Description changed: [Impact] - Autofs direct maps trigger mounts are visible in /etc/mtab. - snmpd iterate over mounts and performs statfs() on them. - This trigger automount to mount them. + Autofs direct map triggers are visible in /etc/mtab. + On boot, when snmpd starts, it iterates over the entries in /etc/mtab and performs statfs() on them. + This trigger automount to mount autofs mounts even if the user does not explicitly access them. + + However this happens only if autofs service is started before snmpd. + If snmpd stars first /etc/mtab is not yet populated with autofs mounts and therefore + are not mounted. + + When there a few autofs mount points the impact is insignificant. + However when there are thousands of them, this causes unnecessary overhead on operations + such as df. + This also delays the system shutdown time since everything needs to be unmounted. [Test Case] - TBD + + *** Test Case 1 - During boot: + + The user that brought this issue to our attention would observe all autofs mounts + be mounted at boot, because in their environment autofs would start first. + + In my environment snmpd starts first so to reproduce I had to add a small delay in + snmpd init script. + + In /etc/init.d/snmp : + @@ -36,6 +36,8 @@ cd / + + case "$1" in + start) + + # Delay snmp start + + sleep 2 + log_daemon_msg "Starting SNMP services:" + # remove old symlink with previous version + if [ -L /var/run/agentx ]; then + + + $cat /etc/auto.master + /- /etc/auto.nfs --timeout=30 + + $cat /etc/auto.nfs + /home/test1 -fstype=nfs,hard,intr,nosuid,no-subtree-check,tcp <NFS server IP>:/srv/export/test1 + /home/test2 -fstype=nfs,hard,intr,nosuid,no-subtree-check,tcp <NFS server IP>:/srv/export/test2 + + Reboot vm, syslog entries : + + # Autofs starts + Jul 11 11:04:16 xenial-vm3 autofs[1295]: * Starting automount... + Jul 11 11:04:16 xenial-vm3 automount[1357]: Starting automounter version 5.1.1, master map /etc/auto.master + Jul 11 11:04:16 xenial-vm3 automount[1357]: using kernel protocol version 5.02 + # Mount triggers, now visible in mtab + Jul 11 11:04:16 xenial-vm3 automount[1357]: mounted direct on /home/test1 with timeout 300, freq 75 seconds + Jul 11 11:04:16 xenial-vm3 automount[1357]: mounted direct on /home/test2 with timeout 300, freq 75 seconds + Jul 11 11:04:16 xenial-vm3 autofs[1295]: ...done. + ... + # SNMP starts + Jul 11 11:04:18 xenial-vm3 snmpd[1294]: * Starting SNMP services: + Jul 11 11:04:18 xenial-vm3 systemd[1]: proc-sys-fs-binfmt_misc.automount: Got automount request for /proc/sys/fs/binfmt_misc, triggered by 1394 (snmpd) + Jul 11 11:04:18 xenial-vm3 systemd[1]: Mounting Arbitrary Executable File Formats File System... + Jul 11 11:04:18 xenial-vm3 systemd[1]: Mounted Arbitrary Executable File Formats File System. + Jul 11 11:04:18 xenial-vm3 automount[1357]: attempting to mount entry /home/test1 <========== + Jul 11 11:04:18 xenial-vm3 kernel: [ 8.880685] FS-Cache: Loaded + Jul 11 11:04:18 xenial-vm3 kernel: [ 8.889318] FS-Cache: Netfs 'nfs' registered for caching + Jul 11 11:04:18 xenial-vm3 kernel: [ 8.902672] NFS: Registering the id_resolver key type + Jul 11 11:04:18 xenial-vm3 kernel: [ 8.902680] Key type id_resolver registered + Jul 11 11:04:18 xenial-vm3 kernel: [ 8.902682] Key type id_legacy registered + Jul 11 11:04:18 xenial-vm3 automount[1357]: mounted /home/test1 <========== + Jul 11 11:04:18 xenial-vm3 automount[1357]: attempting to mount entry /home/test2 <========== + Jul 11 11:04:18 xenial-vm3 kernel: [ 9.163011] random: nonblocking pool is initialized + Jul 11 11:04:18 xenial-vm3 automount[1357]: mounted /home/test2 <=========== + + + *** Test Case 2 - Restart snmpd : + + To reproduce this case, autofs mounts should not be mounted to begin with. + (restart autofs or let it expire) + + #systemctl restart snmpd.service + + Syslog entries : + + Jul 11 11:15:40 xenial-vm3 systemd[1]: Stopping LSB: SNMP agents... + Jul 11 11:15:40 xenial-vm3 snmpd[1668]: * Stopping SNMP services: + Jul 11 11:15:40 xenial-vm3 snmpd[1434]: Received TERM or STOP signal... shutting down... + Jul 11 11:15:40 xenial-vm3 systemd[1]: Stopped LSB: SNMP agents. + Jul 11 11:15:40 xenial-vm3 systemd[1]: Starting LSB: SNMP agents... + Jul 11 11:15:42 xenial-vm3 snmpd[1677]: * Starting SNMP services: + Jul 11 11:15:42 xenial-vm3 automount[1357]: attempting to mount entry /home/test1 <=========== + Jul 11 11:15:42 xenial-vm3 automount[1357]: mounted /home/test1 <=========== + Jul 11 11:15:42 xenial-vm3 automount[1357]: attempting to mount entry /home/test2 <=========== + Jul 11 11:15:42 xenial-vm3 automount[1357]: mounted /home/test2 <=========== + Jul 11 11:15:42 xenial-vm3 snmpd[1684]: /etc/snmp/snmpd.conf: line 145: Warning: Unknown token: defaultMonitors. + Jul 11 11:15:42 xenial-vm3 snmpd[1684]: /etc/snmp/snmpd.conf: line 147: Warning: Unknown token: linkUpDownNotifications. + Jul 11 11:15:42 xenial-vm3 snmpd[1684]: Turning on AgentX master support. + Jul 11 11:15:42 xenial-vm3 systemd[1]: Started LSB: SNMP agents. + Jul 11 11:15:42 xenial-vm3 snmpd[1708]: NET-SNMP version 5.7.3 + [Regression Potential] TBD + + [Other] + + Similar problem : https://sourceforge.net/p/net-snmp/patches/1350/ + + I built a test package with this patch. + PPA : https://launchpad.net/~joalif/+archive/ubuntu/sf227130-test + + - The user reported back that the problem would still persist even with the test + package. + + - Initially while testing it in my environment it would seem that the test package + would not solve the problem entirely. + However, after further rigorous testing I doubt the integrity of my first test results. + I had not taken into account the expiration of mounts. + Autofs mount points were already mounted before installing the test package, the expiration + time was long enough not to be unmounted and therefore when installing the test package + autofs mounts were there which was misleading. + + Now after careful testing it seems that the test package is working. + However, I would like more people to test as well to make sure whether the test + package is actually working or not.
** Tags added: sts -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1835818 Title: snmpd causes autofs mount points to be mounted on system start-up To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/net-snmp/+bug/1835818/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
