Provided by: openafs-client_1.8.10-2.1ubuntu3.4_amd64 
NAME
udebug - Reports Ubik process status for a database server process
SYNOPSIS
udebug -server <server machine> [-port <IP port>]
[-long] [-help]
udebug -s <server machine> [-p <IP port>] [-l] [-h]
DESCRIPTION
The udebug command displays the status of the lightweight Ubik process for the database server process
identified by the -port argument that is running on the database server machine named by the -server
argument. The output identifies the machines where peer database server processes are running, which of
them is the synchronization site (Ubik coordinator), and the status of the connections between them.
OPTIONS
-server <server machine>
Names the database server machine that is running the process for which to display status
information. Provide the machine's IP address in dotted decimal format, its fully qualified host name
(for example, fs1.example.com), or the shortest abbreviated form of its host name that distinguishes
it from other machines. Successful use of an abbreviated form depends on the availability of a name
resolution service (such as the Domain Name Service or a local host table) at the time the command is
issued.
-port <IP port>
Identifies the database server process for which to display status information, either by its process
name or port number. Provide one of the following values:
• buserver or 7021 for the Backup Server
• kaserver or 7004 for the Authentication Server
• ptserver or 7002 for the Protection Server
• vlserver or 7003 for the Volume Location Server
-long
Reports additional information about each peer of the machine named by the -server argument. The
information appears by default if that machine is the synchronization site.
-help
Prints the online help for this command. All other valid options are ignored.
OUTPUT
Several of the messages in the output provide basic status information about the Ubik process on the
machine specified by the -server argument, and the remaining messages are useful mostly for debugging
purposes.
To check basic Ubik status, issue the command for each database server machine in turn. In the output for
each, one of the following messages appears in the top third of the output.
I am sync site . . . (<#_sites> servers)
I am not sync site
For the synchronization site, the following message indicates that all sites have the same version of the
database, which implies that Ubik is functioning correctly. See the following for a description of values
other than "1f".
Recovery state 1f
For correct Ubik operation, the database server machine clocks must agree on the time. The following
messages, which are the second and third lines in the output, report the current date and time according
to the database server machine's clock and the clock on the machine where the udebug command is issued.
Host's <IP_addr> time is <dbserver_date/time>
Local time is <local_date/time> (time differential <skew> secs)
The <skew> is the difference between the database server machine clock and the local clock. Its absolute
value is not vital for Ubik functioning, but a difference of more than a few seconds between the skew
values for the database server machines indicates that their clocks are not synchronized and Ubik
performance is possibly hampered.
Following is a description of all messages in the output. As noted, it is useful mostly for debugging and
most meaningful to someone who understands Ubik's implementation.
The output begins with the following messages. The first message reports the IP addresses that are
configured with the operating system on the machine specified by the -server argument. As previously
noted, the second and third messages report the current date and time according to the clocks on the
database server machine and the machine where the udebug command is issued, respectively. All subsequent
timestamps in the output are expressed in terms of the local clock rather than the database server
machine clock.
Host's addresses are: <list_of_IP_addrs>
Host's <IP_addr> time is <dbserver_date/time>
Local time is <local_date/time> (time differential <skew> secs)
If the <skew> is more than about 10 seconds, the following message appears. As noted, it does not
necessarily indicate Ubik malfunction: it denotes clock skew between the database server machine and the
local machine, rather than among the database server machines.
****clock may be bad
If the udebug command is issued during the coordinator election process and voting has not yet begun, the
following message appears next.
Last yes vote not cast yet
Otherwise, the output continues with the following messages.
Last yes vote for <sync_IP_addr> was <last_vote> secs ago (sync site);
Last vote started <vote_start> secs ago (at <date/time>)
Local db version is <db_version>
The first indicates which peer this Ubik process last voted for as coordinator (it can vote for itself)
and how long ago it sent the vote. The second message indicates how long ago the Ubik coordinator
requested confirming votes from the secondary sites. Usually, the <last_vote> and <vote_start> values are
the same; a difference between them can indicate clock skew or a slow network connection between the two
database server machines. A small difference is not harmful. The third message reports the current
version number <db_version> of the database maintained by this Ubik process. It has two fields separated
by a period. The field before the period is based on a timestamp that reflects when the database first
changed after the most recent coordinator election, and the field after the period indicates the number
of changes since the election.
The output continues with messages that differ depending on whether the Ubik process is the coordinator
or not.
• If there is only one database server machine, it is always the coordinator (synchronization site), as
indicated by the following message.
I am sync site forever (1 server)
• If there are multiple database sites, and the -server argument names the coordinator (synchronization
site), the output continues with the following two messages.
I am sync site until <expiration> secs from now (at <date/time>)
(<#_sites> servers)
Recovery state <flags>
The first message (which is reported on one line) reports how much longer the site remains
coordinator even if the next attempt to maintain quorum fails, and how many sites are participating
in the quorum. The flags field in the second message is a hexadecimal number that indicates the
current state of the quorum. A value of "1f" indicates complete database synchronization, whereas a
value of "f" means that the coordinator has the correct database but cannot contact all secondary
sites to determine if they also have it. Lesser values are acceptable if the udebug command is issued
during coordinator election, but they denote a problem if they persist. The individual flags have the
following meanings:
0x1 This machine is the coordinator.
0x2 The coordinator has determined which site has the database with the highest version number.
0x4 The coordinator has a copy of the database with the highest version number.
0x8 The database's version number has been updated correctly.
0x10
All sites have the database with the highest version number.
If the udebug command is issued while the coordinator is writing a change into the database, the
following additional message appears.
I am currently managing write transaction I<identifier>
• If the -server argument names a secondary site, the output continues with the following messages.
I am not sync site
Lowest host <lowest_IP_addr> was set <low_time> secs ago
Sync host <sync_IP_addr> was set <sync_time> secs ago
The <lowest_IP_addr> is the lowest IP address of any peer from which the Ubik process has received a
message recently, whereas the <sync_IP_addr> is the IP address of the current coordinator. If they
differ, the machine with the lowest IP address is not currently the coordinator. The Ubik process
continues voting for the current coordinator as long as they remain in contact, which provides for
maximum stability. However, in the event of another coordinator election, this Ubik process votes for
the <lowest_IP_addr> site instead (assuming they are in contact), because it has a bias to vote in
elections for the site with the lowest IP address.
For both the synchronization and secondary sites, the output continues with the following messages. The
first message reports the version number of the database at the synchronization site, which needs to
match the <db_version> reported by the preceding "Local db version" message. The second message indicates
how many VLDB records are currently locked for any operation or for writing in particular. The values are
nonzero if the udebug command is issued while an operation is in progress.
Sync site's db version is <db_version>
<locked> locked pages, <writes> of them for write
The following messages appear next only if there are any read or write locks on database records:
There are read locks held
There are write locks held
Similarly, one or more of the following messages appear next only if there are any read or write
transactions in progress when the udebug command is issued:
There is an active write transaction
There is at least one active read transaction
Transaction tid is <tid>
If the machine named by the -server argument is the coordinator, the next message reports when the
current coordinator last updated the database.
Last time a new db version was labelled was:
<last_restart> secs ago (at <date/time>)
If the machine named by the -server argument is the coordinator, the output concludes with an entry for
each secondary site that is participating in the quorum, in the following format.
Server (<IP_address>): (db <db_version>)
last vote rcvd <last_vote> secs ago (at <date/time>),
last beacon sent <last_beacon> secs ago (at <date/time>),
last vote was { yes | no }
dbcurrent={ 0 | 1 }, up={ 0 | 1 } beaconSince={ 0 | 1 }
The first line reports the site's IP address and the version number of the database it is maintaining.
The <last_vote> field reports how long ago the coordinator received a vote message from the Ubik process
at the site, and the <last_beacon> field how long ago the coordinator last requested a vote message. If
the udebug command is issued during the coordinator election process and voting has not yet begun, the
following messages appear instead.
Last vote never rcvd
Last beacon never sent
On the final line of each entry, the fields have the following meaning:
• "dbcurrent" is 1 if the site has the database with the highest version number, 0 if it does not.
• "up" is 1 if the Ubik process at the site is functioning correctly, 0 if it is not.
• "beaconSince" is 1 if the site has responded to the coordinator's last request for votes, 0 if it has
not.
Including the -long flag produces peer entries even when the -server argument names a secondary site, but
in that case only the IP_address field is guaranteed to be accurate. For example, the value in the
<db_version> field is usually 0.0, because secondary sites do not poll their peers for this information.
The values in the last_vote and last_beacon fields indicate when this site last received or requested a
vote as coordinator; they generally indicate the time of the last coordinator election.
EXAMPLES
This example checks the status of the Ubik process for the Volume Location Server on the machine "afs1",
which is the synchronization site.
% udebug afs1 vlserver
Host's addresses are: 192.12.107.33
Host's 192.12.107.33 time is Wed Oct 27 09:49:50 1999
Local time is Wed Oct 27 09:49:52 1999 (time differential 2 secs)
Last yes vote for 192.12.107.33 was 1 secs ago (sync site);
Last vote started 1 secs ago (at Wed Oct 27 09:49:51 1999)
Local db version is 940902602.674
I am sync site until 58 secs from now (at Wed Oct 27 09:50:50 1999) (3 servers)
Recovery state 1f
Sync site's db version is 940902602.674
0 locked pages, 0 of them for write
Last time a new db version was labelled was:
129588 secs ago (at Mon Oct 25 21:50:04 1999)
Server( 192.12.107.35 ): (db 940902602.674)
last vote rcvd 2 secs ago (at Wed Oct 27 09:49:50 1999),
last beacon sent 1 secs ago (at Wed Oct 27 09:49:51 1999), last vote was yes
dbcurrent=1, up=1 beaconSince=1
Server( 192.12.107.34 ): (db 940902602.674)
last vote rcvd 2 secs ago (at Wed Oct 27 09:49:50 1999),
last beacon sent 1 secs ago (at Wed Oct 27 09:49:51 1999), last vote was yes
dbcurrent=1, up=1 beaconSince=1
This example checks the status of the Authentication Server on the machine with IP address 192.12.107.34,
which is a secondary site. The local clock is about 4 minutes behind the database server machine's clock.
% udebug 192.12.107.34 7004
Host's addresses are: 192.12.107.34
Host's 192.12.107.34 time is Wed Oct 27 09:54:15 1999
Local time is Wed Oct 27 09:50:08 1999 (time differential -247 secs)
****clock may be bad
Last yes vote for 192.12.107.33 was 6 secs ago (sync site);
Last vote started 6 secs ago (at Wed Oct 27 09:50:02 1999)
Local db version is 940906574.25
I am not sync site
Lowest host 192.12.107.33 was set 6 secs ago
Sync host 192.12.107.33 was set 6 secs ago
Sync site's db version is 940906574.25
0 locked pages, 0 of them for write
PRIVILEGE REQUIRED
None
SEE ALSO
buserver(8), kaserver(8), ptserver(8), vlserver(8)
COPYRIGHT
IBM Corporation 2000. <http://www.ibm.com/> All Rights Reserved.
This documentation is covered by the IBM Public License Version 1.0. It was converted from HTML to POD
by software written by Chas Williams and Russ Allbery, based on work by Alf Wachsmann and Elizabeth
Cassell.
OpenAFS 2025-05-19 UDEBUG(1)