2009-09-04 15:19:00
Despite it's long life (it's been with us for over ten years now!), BoKS has a number of caveats, or gotchas that one needs to keep in mind at all times. Some of the points below clearly fall in the "not a bug, but a feature" category, but that doesn't mean you shouldn't be aware of them.
So, here's a list of things that can easily lead to problems.
BoKS will not prevent you from re-assigning the same UID to many different users, nor will it prevent the re-use of the same GID for different groups. You may do this intentionally or accidentally. Either way it's a very good idea to regularly check for duplicate UIDs and GIDs. The thing is, if such a duplication occurs on a server it will have a very hard time figuring out to whom a file or a process belongs. Usually this is left up to the order in which the entries occur in /etc/passwd or /etc/group.
Obviously it's best NOT to use duplicate UIDs and GIDs. However, preventing this will require a centralised database of some sorts that all your security personnel refer to and which is used to lay claim to unused IDs.
The exact opposite to the previous is also true: BoKS thinks it's perfectly alright for you to use different UIDs for multiple accounts with the same user name. For example, SUN:peter and AIX:peter may have two completely different UIDs. In the case of normal user accounts this may be problematic, but in the case of applicative accounts (like the "oracle" or "sybase" users) this may lead to disaster.
The same goes for Unix groups: it's possible to have multiple groups with the same names, yet different GIDs. See above for the repercussions.
The way BoKS propagates user accounts and groups to a server is by updating the local security files, such as /etc/passwd and /etc/group. Each time a change is made to a user account BoKS will automatically change the contents of these files. However, there are two issues we have run into with regards to the local security files.
Re item 1: Usually a number of accounts present after a default OS install are not added to BoKS; think of users like uucp, lp, nobody and sys. These accounts may be needed at one point in time, so BoKS will leave any accounts or groups it does not have knowledge of alone. It will work around this information in the local security files. This leads to ...
Re item 2: Unfortunately this means that it's possible for someone with root access to add accounts to the server that cannot be traced. Of course, assuming that BoKS is up and running the account will not be able to be used because there are no access routes. These manual edits however may completely mess up other accounts that -are- in BoKS.
Say for example that BoKS contains a user "oracle" with UID 1234. If the local passwd file happens to contain another "oracle" user with UID 1200 (which was possibly added by a post-install script) things will go horribly wrong.
Manual changes to accounts or groups that -do- exist in BoKS are rectified by BoKS. However, this only occurs when you make a change to an account, after which BoKS overwrites the "faulty" information.
Simply put, BoKS will not issue any warning if there is an overlap of two user accounts made in different host groups. This becomes especially problematic when combined with the second item on this page: no protection against mismatches in UIDs and GIDs.
Let's say we have user accounts SUN:peter (UID 20001) and ORACLE:peter (UID 21003). Now let's say we add SERVERA to both hostgroups SUN and ORACLE. Both "peter" accounts will be added to /etc/passwd with the confusion that is to be expected.
Again, one can prevent a lot of problems by not using different UIDs for the same account. Also, it is a -very- good idea to minimise the amount of copies that exist of one user. I've seen cases where one person had no less than five different accounts, all with the same name but in different host groups. That's easy to mess up!
kilala.nl tags: sysadmin, boks,
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