krenew - Renew a Kerberos v5 ticket
krenew [-bhiLtv] [-c child pid file] [-H minutes]
[-K minutes] [-k ticket file] [-p pid file]
krenew renews an existing renewable ticket. When run without any
arguments, it just attempts to renew the existing ticket-granting
ticket in the current ticket cache, equivalent to "kinit -R", but it
can optionally run a program like aklog to refresh AFS tokens, can run
as a daemon and wake up periodically to renew the ticket cache, or can
run a specified command and keep renewing the ticket cache until the
command finishes (or renewal is no longer possible). If a command is
specified, krenew by default wakes up every 60 minutes (1 hour) to
check the ticket cache.
If a command is given, krenew makes a copy of the ticket cache and
creates a private ticket cache just for that command, thus isolating it
from later destruction of the original ticket cache. This allows
krenew to maintain authentication for a command even if, for example,
the user running the command logs out and OpenSSH destroys their
original ticket cache.
If a command is given, it will not be run using the shell, so if you
want to use shell metacharacters in the command with their special
meaning, give "sh -c command" as the command to run and quote command.
If the command contains command-line options (like "-c"), put "--" on
the command line before the beginning of the command to tell krenew to
not parse those options as its own.
If krenew is built with setpag() support and AFS tokens are requested
with the -t option, it will put the command in a separate PAG before
obtaining AFS tokens so that they don’t interfere with other processes
on the system.
When running a command, krenew propagates HUP, TERM, and QUIT signals
to the child process and does not exit when those signals are received.
(If the propagated signal causes the child process to exit, krenew will
then exit.) This allows krenew to react properly when run under a
command supervision system such as runit(8) or svscan(8) that uses
signals to control supervised commands.
If a running krenew receives an ALRM signal, it immediately refreshes
the ticket cache regardless of whether it is in danger of expiring.
-b After starting, detach from the controlling terminal and run in the
background. This option only makes sense in combination with -K or
a command that krenew will be running. krenew will not background
itself until after it does the initial ticket renewal, so that any
initial errors will be reported, but it will then redirect output
to /dev/null and no subsequent errors will be reported.
If this flag is given, krenew will also change directories to "/".
All paths (such as to a command to run or a PID file) should
therefore be given as absolute, not relative, paths.
If used in conjunction with a command to run, that command will
also run in the background and will also have its input and output
redirected to /dev/null. It will have to report any errors via
some other mechanism for the errors to be seen.
Use of this flag on Mac OS X without specifying a file-based ticket
cache by either using -k or setting KRB5CCNAME will probably not do
what you want. Ticket caches on Mac OS X are, by default, per-
session and with -b krenew will detach itself from your existing
ticket cache. Instead, to renew the default ticket cache on Mac OS
X, try something like:
(krenew -K 60 &)
to run krenew in the background but within the current session.
-c child pid file
Save the process ID (PID) of the child process into child pid file.
child pid file is created if it doesn’t exist and overwritten if it
does exist. This option is only allowed when a command was given
on the command line and is most useful in conjunction with -b to
allow management of the running child process.
Note that, when used with -b, the PID file is written out after
k4start is backgrounded and changes its working directory to /, so
relative paths for the PID file will be relative to / (probably not
what you want).
Only renew the ticket if it has a remaining lifetime of less than
minutes minutes. If either the ticket already has a sufficiently
long remaining lifetime or renewal was successful, run the command
(if one was specified) or exit immediately with status 0 (if none
was). Otherwise, try to renew the ticket so that it will have a
remaining lifetime of at least minutes, exit with an error if
unsuccessful, and then run the command, if any. Cannot be used
-h Display a usage message and exit.
-i Ignore errors in renewing the ticket and keep running. Normally,
krenew exits as soon as it fails to renew the Kerberos ticket
cache. If this flag is given, it will complain about the failure
to standard error (unless -b was given) but continue running,
waking up to try again after the next check interval (see -K).
This is useful if some other process may recreate an expired ticket
cache and krenew should stay around and act on that recreated
ticket cache once it’s present.
Setup errors opening the Kerberos ticket cache or running the
command will still cause krenew to exit, even if this flag is
given. Only Kerberos errors after krenew is running will be
This flag is only useful in daemon mode or when a command was
Run in daemon mode to keep a ticket alive indefinitely. The
program reawakens after minutes minutes, checks if the ticket will
expire before or less than two minutes before the next scheduled
check, and renews the ticket if needed. If this option is not
given but a command was given on the command line, the default
interval is 60 minutes (1 hour).
-k ticket file
Use ticket file as the ticket cache rather than the contents of the
environment variable KRB5CCNAME or the library default. ticket
file should be the path to a file, without any leading "FILE:"
string. Using this option forces a file-based ticket cache; if you
wish to use a different type of ticket cache, don’t specify -k and
instead set KRB5CCNAME to the designator of the cache you wish to
-L Report messages to syslog as well as to standard output or standard
error. All messages will be logged with facility LOG_DAEMON.
Regular messages that are displayed on standard output are logged
with level LOG_NOTICE. Errors that don’t cause krenew to terminate
when run with -i are logged with level LOG_WARNING. Fatal errors
are logged with level LOG_ERR.
This is useful when debugging problems in combination with -b.
-p pid file
Save the process ID (PID) of the running krenew process into pid
file. pid file is created if it doesn’t exist and overwritten if
it does exist. This option is most useful in conjunction with -b
to allow management of the running krenew daemon.
Note that, when used with -b the PID file is written out after
krenew is backgrounded and changes its working directory to /, so
relative paths for the PID file will be relative to / (probably not
what you want).
-t Run an external program after getting a ticket. The default use of
this is to run aklog to get a token. If the environment variable
KINIT_PROG is set, it overrides the compiled-in default.
If krenew has been built with AFS setpag() support and a command
was given on the command line, krenew will create a new PAG before
obtaining AFS tokens. Otherwise, it will obtain tokens in the
-v Be verbose. This will print out a bit of additional information
about what is being attempted and what the results are.
The program normally exits with status 0 if it successfully renews a
ticket. If krenew runs aklog or some other program krenew returns the
exit status of that program.
Renew the current ticket-granting ticket.
Wake up every ten minutes and check to see if the ticket cache needs
renewing. If it does, re-run aklog as well.
krenew -K 10 -t
Run the program /usr/local/bin/compute-job in the background, checking
every hour to see if the ticket needs to be renewed (the default). Put
the PID of the krenew job in /var/run/compute.pid. Obtain a new AFS
token each time the ticket has to be renewed.
krenew -b -t -p /var/run/compute.pid /usr/local/bin/compute-job
If you wanted to pass options to /usr/local/bin/compute-job, putting a
"--" argument before it would be necessary to keep krenew from
interpreting those options as its own.
If you want to redirect output to a file that requires authentication
to write to, you will need to do that redirection in a sub-shell. In
other words, the following command:
krenew -t compute-job > /afs/local/data/output
won’t work if /afs/local/data/output requires an AFS token to write to.
The job, while running, will have an AFS token, but the output
redirection is done in the parent shell and doesn’t benefit from
krenew. The above should instead be written as:
krenew -t -- sh -c 'compute-job > /afs/local/data/output'
With this command, the shell doing the redirection will also be run
under krenew and have the benefit of the AFS token it obtains.
If the environment variable AKLOG is set, its value will be used as the
program to run with -t rather than the default complied into krenew.
If AKLOG is not set and KINIT_PROG is set, its value will be used
instead. KINIT_PROG is honored for backward compatibility but its use
is not recommended due to its confusing name.
If no ticket file (with -k) or command is specified on the command
line, krenew will use the environment variable KRB5CCNAME to determine
the location of the the ticket granting ticket. If the -k option is
used, KRB5CCNAME will be set to point to the ticket file before running
the aklog program or any command given on the command line.
The default ticket cache is determined by the underlying Kerberos
libraries. The default path for aklog is determined at build time, and
will normally be whichever of aklog or afslog is found in the user’s
The kstart web page at <http://www.eyrie.org/~eagle/software/kstart/>
will have the current version of krenew.
krenew was written by Russ Allbery <firstname.lastname@example.org>. It was based
heavily on k5start by Booker C. Bense, which in turn was based on the
k4start code written by Robert Morgan.