1.切换到普通用户下，不出现，用户名@主机ip, 环境变量被破坏，
参考：一文教你快速修改ubuntu终端显示的主机名和用户名_ubuntu终端名称-CSDN博客
2.如果登陆进去无法使用ls,cd，vi等命令
2.1 环境变量
如果 PATH 被清空，用户无法执行任何命令。
临时恢复 PATH（如果当前 Shell 允许）：
export PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
然后检查是否能运行 ls、vi 等命令。
永久：此用户下 vi ~/.bashrc （不用sudo）
# ~/.bashrc: executed by bash(1) for non-login shells.
# see /usr/share/doc/bash/examples/startup-files (in the package bash-doc)
# for examples# If not running interactively, don't do anything
case $- in*i*) ;;*) return;;
esac# don't put duplicate lines or lines starting with space in the history.
# See bash(1) for more options
HISTCONTROL=ignoreboth# append to the history file, don't overwrite it
shopt -s histappend# for setting history length see HISTSIZE and HISTFILESIZE in bash(1)
HISTSIZE=1000
HISTFILESIZE=2000# check the window size after each command and, if necessary,
# update the values of LINES and COLUMNS.
shopt -s checkwinsize# If set, the pattern "**" used in a pathname expansion context will
# match all files and zero or more directories and subdirectories.
#shopt -s globstar# make less more friendly for non-text input files, see lesspipe(1)
[ -x /usr/bin/lesspipe ] && eval "$(SHELL=/bin/sh lesspipe)"# set variable identifying the chroot you work in (used in the prompt below)
if [ -z "${debian_chroot:-}" ] && [ -r /etc/debian_chroot ]; thendebian_chroot=$(cat /etc/debian_chroot)
fi# set a fancy prompt (non-color, unless we know we "want" color)
case "$TERM" inxterm-color|*-256color) color_prompt=yes;;
esac# uncomment for a colored prompt, if the terminal has the capability; turned
# off by default to not distract the user: the focus in a terminal window
# should be on the output of commands, not on the prompt
#force_color_prompt=yesif [ -n "$force_color_prompt" ]; thenif [ -x /usr/bin/tput ] && tput setaf 1 >&/dev/null; then# We have color support; assume it's compliant with Ecma-48# (ISO/IEC-6429). (Lack of such support is extremely rare, and such# a case would tend to support setf rather than setaf.)color_prompt=yeselsecolor_prompt=fi
fiif [ "$color_prompt" = yes ]; thenPS1='${debian_chroot:+($debian_chroot)}\[\033[01;32m\]\u@\h\[\033[00m\]:\[\033[01;34m\]\w\[\033[00m\]\$ '
elsePS1='${debian_chroot:+($debian_chroot)}\u@\h:\w\$ '
fi
unset color_prompt force_color_prompt# If this is an xterm set the title to user@host:dir
case "$TERM" in
xterm*|rxvt*)PS1="\[\e]0;${debian_chroot:+($debian_chroot)}\u@\h: \w\a\]$PS1";;
*);;
esac# enable color support of ls and also add handy aliases
if [ -x /usr/bin/dircolors ]; thentest -r ~/.dircolors && eval "$(dircolors -b ~/.dircolors)" || eval "$(dircolors -b)"alias ls='ls --color=auto'#alias dir='dir --color=auto'#alias vdir='vdir --color=auto'alias grep='grep --color=auto'alias fgrep='fgrep --color=auto'alias egrep='egrep --color=auto'
fi# colored GCC warnings and errors
#export GCC_COLORS='error=01;31:warning=01;35:note=01;36:caret=01;32:locus=01:quote=01'# some more ls aliases
alias ll='ls -alF'
alias la='ls -A'
alias l='ls -CF'# Add an "alert" alias for long running commands. Use like so:
# sleep 10; alert
alias alert='notify-send --urgency=low -i "$([ $? = 0 ] && echo terminal || echo error)" "$(history|tail -n1|sed -e '\''s/^\s*[0-9]\+\s*//;s/[;&|]\s*alert$//'\'')"'# Alias definitions.
# You may want to put all your additions into a separate file like
# ~/.bash_aliases, instead of adding them here directly.
# See /usr/share/doc/bash-doc/examples in the bash-doc package.if [ -f ~/.bash_aliases ]; then. ~/.bash_aliases
fi# enable programmable completion features (you don't need to enable
# this, if it's already enabled in /etc/bash.bashrc and /etc/profile
# sources /etc/bash.bashrc).
if ! shopt -oq posix; thenif [ -f /usr/share/bash-completion/bash_completion ]; then. /usr/share/bash-completion/bash_completionelif [ -f /etc/bash_completion ]; then. /etc/bash_completionfi
fi
export PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:$PATH
export PATH=/opt/mips-gcc540-glibc222-64bit-r3.3.0/bin:$PATH
再source ~/.bashrc(不用sudo)
2.2或者权限问题：权限问题用root进去修改如下：
root@ubuntu:~# sudo usermod -s /bin/bash lhj
root@ubuntu:~# sudo chmod 755 /home/lhj
root@ubuntu:~# sudo chown -R lhj:lhj /home/lhj
cd ~回到家目录
3.su - lhj 切换后无法正确加载环境变量
可能原因：
1. ~/.bashrc 或 ~/.profile 未被正确加载
su - lhj 应该会加载 ~/.profile 或 ~/.bash_profile，但可能：
# 查看 ~/.profile 是否存在
ls -l ~/.profile# 查看 ~/.bashrc 是否存在
ls -l ~/.bashrc# 如果文件不存在，从 /etc/skel 复制默认配置
cp /etc/skel/.bashrc ~/
cp /etc/skel/.profile ~/确保 PATH 正确设置
export PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:$PATH"
source ~/.profile
2. /etc/environment 或 /etc/profile 覆盖了 PATH
cat /etc/environment
sudo nano /etc/environment
PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"