Linux – How to Diff Two Config Files

configurationdiff()linux

I've got two snmpd.conf files, one on a server that works, and one that doesn't. How can I diff the two config files while stripping out irrelevant comments and newlines?

Best Answer

diff <(grep -v '^#' f1) <(grep -v '^#' f2)

To avoid blank lines, and lines containing nothing but spaces, in addition to identical lines that have a single difference of added leading spaces...

diff -b \
  <(grep -vE '^([ \t]*#|^[ \t]*$)' f1)\
  <(grep -vE '^([ \t]*#|^[ \t]*$)' f2)

By this point though, I'd probably put that into a script and write something like the original suggestion that's a little more readable.

Related Solutions

Linux File Permissions – Best Way to Handle Apache 2’s www-data User in /var/www

Attempting to expand on @Zoredache's answer, as I give this a go myself:

Create a new group (www-pub) and add the users to that group

groupadd www-pub

usermod -a -G www-pub usera ## must use -a to append to existing groups

usermod -a -G www-pub userb

groups usera ## display groups for user
Change the ownership of everything under /var/www to root:www-pub

chown -R root:www-pub /var/www ## -R for recursive
Change the permissions of all the folders to 2775

chmod 2775 /var/www ## 2=set group id, 7=rwx for owner (root), 7=rwx for group (www-pub), 5=rx for world (including apache www-data user)

Set group ID (SETGID) bit (2) causes the group (www-pub) to be copied to all new files/folders created in that folder. Other options are SETUID (4) to copy the user id, and STICKY (1) which I think lets only the owner delete files.

There's a -R recursive option, but that won't discriminate between files and folders, so you have to use find, like so:

find /var/www -type d -exec chmod 2775 {} +
Change all the files to 0664

find /var/www -type f -exec chmod 0664 {} +
Change the umask for your users to 0002

The umask controls the default file creation permissions, 0002 means files will have 664 and directories 775. Setting this (by editing the umask line at the bottom of /etc/profile in my case) means files created by one user will be writable by other users in the www-group without needing to chmod them.

Test all this by creating a file and directory and verifying the owner, group and permissions with ls -l.

Note: You'll need to logout/in for changes to your groups to take effect!

SSH – How to Perform Diff Over SSH

You can do it with Bash's process substitution:

 diff foo <(ssh myServer 'cat foo')

Or, if both are on remote servers:

diff <(ssh myServer1 'cat foo') <(ssh myServer2 'cat foo')

Best Answer

Related Solutions

Linux File Permissions – Best Way to Handle Apache 2’s www-data User in /var/www

SSH – How to Perform Diff Over SSH

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