"WARNING: terminal is not fully functional" when using "man" as root

Question

I know that this question has been posted a zillion times, but none of the answers I could find have solved it for me.

I have a root shell given by sudo bash. When I try to use man, I have this message:

WARNING: terminal is not fully functional
-  (press RETURN)

and limited control on navigation.

It works when I'm not root. As root, aptitude works correctly. I've tried to export TERM with: linux, xterm, xterm-color, xterm-256color, ansi, screen-256color, ncurses, vt100.

The ouput of stty -a is exactly the same as root and non-root:

speed 38400 baud; rows 30; columns 271; line = 0;
intr = ^C; quit = ^\; erase = ^?; kill = ^U; eof = ^D; eol = <undef>; eol2 = <undef>; swtch = <undef>; start = ^Q; stop = ^S; susp = ^Z; rprnt = ^R; werase = ^W; lnext = ^V; discard = ^O; min = 1; time = 0;
-parenb -parodd -cmspar cs8 -hupcl -cstopb cread -clocal -crtscts
-ignbrk -brkint -ignpar -parmrk -inpck -istrip -inlcr -igncr icrnl ixon -ixoff -iuclc -ixany -imaxbel iutf8
opost -olcuc -ocrnl onlcr -onocr -onlret -ofill -ofdel nl0 cr0 tab0 bs0 vt0 ff0
isig icanon iexten echo echoe echok -echonl -noflsh -xcase -tostop -echoprt echoctl echoke -flusho -extproc

I'm stuck.

Any idea?

Thanks in advance

Answer 1

I ended up solving this myself by adding a missing ncurses package which provides /usr/share/terminfo. This package, which for whatever reason of package dependency hell, wasn't installed, seems to fix this. Though in my case it happened to both root and non-root users alike, so it might not be it, but worth posting I think in case anyone is in my situation in the future and comes across this question in Google results.

On CentOS, it's ncurses-base.

On Debian 11 (and likely Ubuntu's), it's ncurses-term.

If you're missing those packages, try installing them and seeing if that helps.

I found this by trying to do reset on the terminal, and the resulting "Terminal type?" prompt rejecting everything I tried, e.g.

Terminal type? screen                                      
reset: unknown terminal type screen
Terminal type?                                             
Terminal type? vt100
reset: unknown terminal type vt100

That got me comparing it against a working system, and looking for anything that included the name vt100. A bit of digging through the grep -r results led me to the files under /usr/share/terminfo which were missing on the "bad" system. A call to rpm -q --whatprovides /usr/share/terminfo/v/vt100 led me to that package name.

Answer 2

Almost 3 years later, ChatGPT gave me the solution...

# type man
man is aliased to `TERMINFO=~/.terminfo/ LESS=C TERM=mostlike PAGER=less man'

at some point "man" was aliased to a bogus line... that explains why the other users were unaffected...