Some thoughts on log rolling with date extensions

July 22, 2015

For a long time everyone renamed old logs in the same way; the most recent log got a .0 on the end, the next most recent got a .1 on the end, and so on. About the only confusion between systems was that some started from .0 and some from .1, and also whether or not your logs got gzip'd. These days, the Red Hat and Fedora derived Linuxes have switched to lograte's dateext setting, where the extension that old logs get is date based, generally in the format -YYYYMMDD. I'm not entirely sure how I feel about this so far and not just because it changes what I'm used to.

On the good side, this means that a rolled log has the same file name for as long as it exists. If I look at allmessages-20150718 today, I know that I can come back tomorrow or next week and find it with the same name; I don't have to remember that what was allmessages.3 today is allmessages.4 tomorrow (or next week). It also means that logs sort lexically in time order, which is not the case with numbered logs; .10 is lexically between .1 and .2, but is nowhere near them in time.

(The lexical order is also forward time order instead of reverse time order, which means that if you grep everything you get it in forward time order instead of things jumping around.)

On the down side, rolled logs having a date extension means that I can no longer look at the most recently rolled log just by using <name>.0 (or .1); instead I need to look at what log files there are (this is especially the case with logs that are rolled weekly). It also means that I lose the idiom of grep'ing or whatever through <name>.[0-6] to look through the last week's worth of logs; again, I need to look at the actual filenames or at least resort to something like 'grep ... $(/bin/ls -1t <name>.* | sed 7q)' (and I can do that with any log naming scheme).

I'm sure that Red Hat had its reasons to change the naming scheme around. It certainly makes a certain amount of things consistent and obvious. But on the whole I'm not sure I actually like it or if I'd rather have things be the old fashioned way that Ubuntu and others still follow.

(I don't care enough about this to change my Fedora machines or our CentOS 6 and 7 servers.)

Written on 22 July 2015.
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Last modified: Wed Jul 22 01:21:45 2015
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