Sstrhsrtj

My /etc/group has grown by adding new users as well as installing programs that have added their own user and/or group. The same is true for /etc/passwd. Editing has now become a little cumbersome due to the lack of structure.

May I sort these files (e.g. by numerical id or alphabetical by name) without negative effect on the system and/or package managers?

I would guess that is does not matter but just to be sure I would like to get a 2nd opinion. Maybe root needs to be the 1st line or within the first 1k lines or something?

The same goes for /etc/*shadow.

You should be OK doing this: in fact, according to the article and reading the documentation, you can sort /etc/passwd and /etc/group by UID/GID with pwck -s and grpck -s, respectively.

Although ErikF is correct that this should generally be okay, I do want to point out one potential issue:

You're allowed to map different usernames to the same UID. If you make use of this, tools that map a UID back to a username will generally pick the first username they find for that UID in /etc/passwd. Sorting may cause a different username to appear first. For display purposes (e.g. ls -l output), either username should work, but it's possible that you've configured some program to accept requests from username A, where it will deny those requests if it sees them coming from username B, even if A and B are the same user.

Having root at first line has been a long time de facto "standard" and is very convenient if you ever have to fix their shell or delete the password, when dealing with problems or recovering systems.

Likewise I prefer to have daemons/utils users in the middle and standard users at the end of both passwd and shadow.

hvd answer is also very good about disturbing the users order, especially in systems with many users maintained by hand.

If you somewhat manage to sort the files, for instance, only for standard users, it would be more sensible than changing the order of all users, imo.

Here is a bit of somewhat hairy bash code to similarly sort the shadow/gshadow files safely (using vipw -s/vigr -s) and in-place from the command line:

EDITOR="/usr/bin/vi -c "1,\$!awk 'BEGIN {FS = \":\"} FNR==NR {x2[\$1] = \$0; next} \$1 in x2 {print x2 [\$1]}' - /etc/passwd ^V^J

:wq" >/dev/null 2>&1" vipw -s



EDITOR="/usr/bin/vi -c "1,\$!awk 'BEGIN {FS = \":\"} FNR==NR {x2[\$1] = \$0; next} \$1 in x2 {print x2 [\$1]}' - /etc/group ^V^J

  :wq" >/dev/null 2>&1" vigr -s

NOTE:

1. 
   ^V^J is CtrlVCtrlJ which generates a new line - this new line is needed to separate the vim command lines.


2. 
   vi -c passes the command to the vim editor which is assigned to be the editor for vipw/vigr by the EDITOR variable


3. The awk code sorts shadow by passwd (and gshadow by group)


4. The backslashes are just the multiple levels of escape needed corresponding to the quotation levels.