Category: Tips & Tricks

When using Syncrepl…

rthomson Leave a comment

Quick OpenLDAP tip boys & girls…

When using syncrepl to replicate from a master LDAP server to a slave LDAP server, always remember to configure the ACLs on the master LDAP server to allow the “sync dn” to read everything.

I know it sounds entirely obvious but today I realized that the order in which I had defined the ACLs on the master LDAP server was preventing the sync dn from reading the “userPassword” attribute and thus also preventing it from syncing it to the slave. The consequence of which was that users would not be able to authenticate against the slave server! Shit!

Of course, since everything else was syncing properly, all the NSS (lookup) stuff worked fine but anything authentication related like PAM wouldn’t work because the user bind would fail with “Invalid credentials” in /var/log/secure. It had a been some time since I tested authentication so I must never have actually tested authentication against the slave (whoops!) and thus didn’t notice until now. I know I tested lookups but testing authentication must have slipped by somehow. Grrr, testing.

Good thing I caught the problem early and it never escalated into a problem, that really could have sucked down the line.

Don’t make the same mistake I did.

Atempo Time Navigator 4.2 Archive Media Selection Tunable

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Just a quick post here to share a non-obvious tunable for Atempo’s Time Navigator 4.2 regarding archiving and media selection.

Before upgrading from 4.1 to 4.2 Time Navigator’s media selection for archive jobs with standalone drives behaved as expected: If existing partly filled and open cartridges in the associated media pool existed, Time Navigator would request those media be placed in the drives upon the start a new archive operation, effectively only asking for new, unlabeled media to be inserted once the existing media was full.

However, with the upgrade to 4.2 we found that Time Navigator was no longer requesting the existing, partly filled, open cartridges and was instead requesting new, unlabeled media to be inserted into the drives instead! The result of this new behavior was that Time Navigator would use new tapes for every new archive operation, no matter if existing, partly filled and open media was available in the media pool. Basically 4.2’s default behavior was preventing us from filling any archive media unless the particular archive job would happen to be larger than a single tape.

While I don’t know why the functionality changed, I do know what tunable to modify in order to make 4.2 behave like 4.1. The tunable is “check_external_cart_when_recycling“. Setting this tunable to “Yes” has restored the 4.1 behavior, allowing us to make full use of all archive media capacity by only requesting new media when all the existing media in the media pool has been filled.

I believe we only faced this problem because we use standalone archive tape drives that do not have an autoloader or robot nor an “inventory” of online tape. Each tape must be manually loaded. I suspect that if we had an autoloader for our tape drives, that 4.2 would have made the correct/expected selection of media.

I doubt that anyone else is going to face this problem but it took about 3 weeks with Atempo’s R&D department to figure out the problem so I figure if posting here can save anyone that amount of time, then I’ll have done my part!

How to Kill All Your Processes

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Here’s a quick tip for killing your processes on Linux/UNIX:

kill -1 -1

The first -1 is the signal you are going to send and the second -1 means “every process”. The -1 signal is SIGHUP (hang up) which is basically a nice way of asking a process to terminate (or reload in some cases). The reason sending SIGHUP to every process works to kill only the processes of the account that ran the command is that not every process will respond signals from just anyone. Only processes running at the user who executes the above command will respond to it. Other users processes, including those running as root will not respond. Be careful however, running this as root will attempt to kill ALL processes.

Not all processes will respond to SIGHUP by exiting so sometimes more force is necessary:

kill -9 -1

The -9 signal is SIGKILL (kill program) which should take care of any pesky processes that don’t want to exit nicely.

And that’s that.