linux

tty를 닫았다가 다시 열지 못하는 경우 (즉, 로그 오프했다가 다시 로그온하면 프로세스의 일부 백그라운드 프로세스가 종료 될 수 있음) 한 가지만 선택할 수 있습니다.

• gdb를 사용하여 해당 프로세스에 연결하고 다음을 실행하십시오.
  • p dup2 (열기 ( “/ dev / null”, 0), 1)
  • p dup2 (열기 ( “/ dev / null”, 0), 2)
  • 떼다
  • 떠나다

예 :

$ tail -f /var/log/lastlog &
[1] 5636

$ ls -l /proc/5636/fd
total 0
lrwx------ 1 myuser myuser 64 Feb 27 07:36 0 -> /dev/pts/0
lrwx------ 1 myuser myuser 64 Feb 27 07:36 1 -> /dev/pts/0
lrwx------ 1 myuser myuser 64 Feb 27 07:36 2 -> /dev/pts/0
lr-x------ 1 myuser myuser 64 Feb 27 07:36 3 -> /var/log/lastlog

$ gdb -p 5636
GNU gdb 6.8-debian
Copyright (C) 2008 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-linux-gnu".
Attaching to process 5636
Reading symbols from /usr/bin/tail...(no debugging symbols found)...done.
Reading symbols from /lib/librt.so.1...(no debugging symbols found)...done.
Loaded symbols for /lib/librt.so.1
Reading symbols from /lib/libc.so.6...(no debugging symbols found)...done.
Loaded symbols for /lib/libc.so.6
Reading symbols from /lib/libpthread.so.0...(no debugging symbols found)...done.
[Thread debugging using libthread_db enabled]
[New Thread 0x7f3c8f5a66e0 (LWP 5636)]
Loaded symbols for /lib/libpthread.so.0
Reading symbols from /lib/ld-linux-x86-64.so.2...(no debugging symbols found)...done.
Loaded symbols for /lib64/ld-linux-x86-64.so.2

(no debugging symbols found)
0x00007f3c8eec7b50 in nanosleep () from /lib/libc.so.6

(gdb) p dup2(open("/dev/null",0),1)
[Switching to Thread 0x7f3c8f5a66e0 (LWP 5636)]
$1 = 1

(gdb) p dup2(open("/dev/null",0),2)
$2 = 2

(gdb) detach
Detaching from program: /usr/bin/tail, process 5636

(gdb) quit

$ ls -l /proc/5636/fd
total 0
lrwx------ 1 myuser myuser 64 Feb 27 07:36 0 -> /dev/pts/0
lrwx------ 1 myuser myuser 64 Feb 27 07:36 1 -> /dev/null
lrwx------ 1 myuser myuser 64 Feb 27 07:36 2 -> /dev/null
lr-x------ 1 myuser myuser 64 Feb 27 07:36 3 -> /var/log/lastlog
lr-x------ 1 myuser myuser 64 Feb 27 07:36 4 -> /dev/null
lr-x------ 1 myuser myuser 64 Feb 27 07:36 5 -> /dev/null

다음을 고려할 수도 있습니다.

• 사용하여 screen; 화면은 새로운 SSH / telnet / etc, 세션을 열지 않고도 전환 할 수있는 여러 가상 TTY를 제공합니다.
• 사용하여 nohup; 이를 통해 프로세스의 백그라운드 프로세스를 잃지 않고 세션을 닫았다가 다시 열 수 있습니다.

답변

strace -ewrite -p $PID

strace -ewrite -p $PID 2>&1 | grep "write(1" 

p dup2(open("/dev/null",0),1)
p dup2(open("/dev/null",0),2)
detach
quit

#!/bin/sh
if [ "$0" -a "$1" ]; then
 gdb -p $1 -x $0.gdb
else
 echo Must specify PID of process to silence >&2
fi

chmod +x ~/bin/silence  # make the script executable

ps  # look for process xulrunner-stub (in this case we saw the PID in the error above)
silence 5117  # run the script, using PID we found

tty
ls -l /proc/20818/fd
gdb -p 20818

p close(1)
p open("/dev/pts/4", 1)
p close(2)
p open("/tmp/myerrlog", 1)
q

[Ctrl+z]
bg %1 && disown %1
[Ctrl+d]

#!/bin/bash

pid=$(cat /var/run/app/app.pid)
logFile="/var/log/app.log"

reloadLog()
{
    if [ "$pid" = "" ]; then
        echo "invalid PID"
    else
        gdb -p $pid >/dev/null 2>&1 <<LOADLOG
p close(1)
p open("$logFile", 1)
p close(2)
p open("$logFile", 1)
q
LOADLOG
        LOG_FILE=$(ls /proc/${pid}/fd -l | fgrep " 1 -> " | awk '{print $11}')
        echo "log file set to $LOG_FILE"
    fi
}

reloadLog