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I'm new to OS X. I'm running OS X Lion on a MacBook Pro. Is it safe to upgrade the bash shell using Homebrew:

$ brew install bash

If safe, how do I make it the default instance of the shell I run through Terminal?

Thanks!

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3 Answers

up vote 30 down vote accepted

Binaries in /{,usr/}{,s}bin/ should not usually be replaced with other files. Other programs expect them to be the versions that came with OS X, and they are replaced by OS upgrades.

After running brew install bash, you can change the default shell safely by:

  • Adding /usr/local/bin/bash to /etc/shells
  • Running chsh -s /usr/local/bin/bash.

Settings in Terminal or iTerm 2 don't normally have to be changed. Both of them default to opening new windows with a login shell of the default shell.

The default shell can also be changed from System Preferences or with dscl, but all three options just modify /var/db/dslocal/nodes/Default/users/$USER.plist.

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Looks like it worked, and if I experience any issues it should be easy to roll back! Thanks! – Rudy Sep 9 '11 at 21:52
did not know that advanced option page was there. Sweet! – lemonginger Sep 10 '11 at 0:20
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The bit about editing /etc/shells to include the brew-installed bash is required. Otherwise (at least on my machine) Terminal will refuse to start. – brendanjerwin Feb 20 '12 at 23:38
up vote 0 down vote

Well before you do anything, back up your current file (of course, but always deserves to be said)

sudo cp /bin/bash /bin/bash.3.2.bk

Then create a symlink to the bash executable that Homebrew downloaded. I think it will be in /usr/local/Cellar, like so

sudo ln -s /usr/local/Cellar/bash/4.2.10/bin/bash /bin/bash

Now /bin/bash points to the file in your usr/local directory

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The downside of plopping a new bash in for the system version is any update of the OS can erase your preferred shell. Presumably the OP wants to use new features which could break if the OS installs a "newer than old OS" but "older than custom" version of bash. Better to change the default path or change the user shell variable. – bmike♦ Sep 9 '11 at 22:58
well, you could just create a new simlink since it wouldn't overwrite the version of bash in your usr/local directory. but you are correct, Daniel's way is prob better – lemonginger Sep 9 '11 at 23:36
Ooh - edit your answer please to put that first (and keep the original idea if you prefer as a second alternative - I like that much better and would love a chance to reverse my vote :-) – bmike♦ Sep 9 '11 at 23:38
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hmm, well that /is/ what I said, but I edited to try to clarify what each step does a little better. Still think top rated answer is prob better though :) – lemonginger Sep 9 '11 at 23:44
This seems like a pretty dangerous way to go about changing the system shell. – Samuel Mikel Bowles Sep 10 '11 at 0:26
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up vote 0 down vote

I could be wrong here, but as far as I know brew would install it's own instance of bash, since brew works under /usr/bin while the default bash works under /bin.

About Terminal, you can make shells open with your own, custom command. Go to Preferences > Startup and select Shells open with: Command (complete path). Simply type the path to your new bash and vuala!

Hope it helps!

BTW: Backup! Best advice in this situations!

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