Linux Admin 简明教程
Linux Admin - Process Management
以下是与进程管理一起使用的常用命令：bg、fg、nohup、ps、pstree、top、kill、killall、free、uptime、nice。
Following are the common commands used with Process Management–bg, fg, nohup, ps, pstree, top, kill, killall, free, uptime, nice.
Work with Processes
Quick Note − Process PID in Linux
Quick Note − Process PID in Linux
在 Linux 中，每个正在运行的进程都被赋予一个 PID 或进程 ID 号码。这个 PID 就是 CentOS 识别特定进程的方式。正如我们所讨论的，systemd 是第一个启动的进程并在 CentOS 中被赋予 PID 1。
In Linux every running process is given a PID or Process ID Number. This PID is how CentOS identifies a particular process. As we have discussed, systemd is the first process started and given a PID of 1 in CentOS.
Pgrep 用于获取给定进程名称的 Linux PID。
Pgrep is used to get Linux PID for a given process name.
[root@CentOS]# pgrep systemd
1
[root@CentOS]#如你所见，pgrep 命令返回了 systemd 的当前 PID。
As seen, the pgrep command returns the current PID of systemd.
Basic CentOS Process and Job Management in CentOS
在 Linux 中处理进程时，了解如何在命令行中执行基本的前台和后台进程非常重要。
When working with processes in Linux it is important to know how basic foregrounding and backgrounding processes is performed at the command line.
-
fg − Bringsthe process to the foreground
-
bg − Movesthe process to the background
-
jobs − List of the current processes attached to the shell
-
ctrl+z − Control + z key combination to sleep the current process
-
& − Startsthe process in the background
让我们开始使用 shell 命令 sleep。 sleep 只会做它所命名的工作，在定义的时间段内 sleep。
Let’s start using the shell command sleep. sleep will simply do as it is named, sleep for a defined period of time − sleep.
[root@CentOS ~]$ jobs
[root@CentOS ~]$ sleep 10 &
[1] 12454
[root@CentOS ~]$ sleep 20 &
[2] 12479
[root@CentOS ~]$ jobs
[1]- Running sleep 10 &
[2]+ Running sleep 20 &
[cnetos@CentOS ~]$现在，我们将第一个作业置于前台 −
Now, let’s bring the first job to the foreground −
[root@CentOS ~]$ fg 1
sleep 10如果你有留意，你便会注意到前台作业卡在你的 shell 中了。现在，我们将进程设为休眠，然后在后台重新启用它。
If you are following along, you’ll notice the foreground job is stuck in your shell. Now, let’s put the process to sleep, then re-enable it in the background.
-
Hit control+z
-
Type: bg 1, sending the first job into the background and starting it.
[root@CentOS ~]$ fg 1
sleep 20
^Z
[1]+ Stopped sleep 20
[root@CentOS ~]$ bg 1
[1]+ sleep 20 &
[root@CentOS ~]$nohup
在从 shell 或终端进行操作时，值得注意的是，默认情况下，当 shell 关闭或用户注销时，附加至 shell 的所有进程和作业都会终止。在使用 nohup 时，如果用户注销或关闭附加该进程的 shell，进程将继续运行。
When working from a shell or terminal, it is worth noting that by default all the processes and jobs attached to the shell will terminate when the shell is closed or the user logs out. When using nohup the process will continue to run if the user logs out or closes the shell to which the process is attached.
[root@CentOS]# nohup ping www.google.com &
[1] 27299
nohup: ignoring input and appending output to ‘nohup.out’
[root@CentOS]# pgrep ping
27299
[root@CentOS]# kill -KILL `pgrep ping`
[1]+ Killed nohup ping www.google.com
[root@CentOS rdc]# cat nohup.out
PING www.google.com (216.58.193.68) 56(84) bytes of data.
64 bytes from sea15s07-in-f4.1e100.net (216.58.193.68): icmp_seq = 1 ttl = 128
time = 51.6 ms
64 bytes from sea15s07-in-f4.1e100.net (216.58.193.68): icmp_seq = 2 ttl = 128
time = 54.2 ms
64 bytes from sea15s07-in-f4.1e100.net (216.58.193.68): icmp_seq = 3 ttl = 128
time = 52.7 msps Command
ps 命令通常由管理员使用，以调查特定进程的快照。ps 通常与 grep 配合使用，以筛选出特定进程进行分析。
The ps command is commonly used by administrators to investigate snapshots of a specific process. ps is commonly used with grep to filter out a specific process to analyze.
[root@CentOS ~]$ ps axw | grep python
762 ? Ssl 0:01 /usr/bin/python -Es /usr/sbin/firewalld --nofork -nopid
1296 ? Ssl 0:00 /usr/bin/python -Es /usr/sbin/tuned -l -P
15550 pts/0 S+ 0:00 grep --color=auto python在上方的命令中，我们看到了所有使用 Python 解释器的进程。结果中还包含我们的 grep 命令，它查找字符串 python。
In the above command, we see all the processes using the python interpreter. Also included with the results were our grep command, looking for the string python.
以下是与 ps 配合使用时最常见的命令行开关。
Following are the most common command line switches used with ps.
Switch |
Action |
a |
Excludes constraints of only the reporting processes for the current user |
x |
Shows processes not attached to a tty or shell |
w |
Formats wide output display of the output |
e |
Shows environment after the command |
-e |
Selects all processes |
-o |
User-defined formatted output |
-u |
Shows all processes by a specific user |
-C |
Shows all processes by name or process id |
--sort |
Sorts the processes by definition |
查看 nobody 用户正在使用的所有进程
To see all processes in use by the nobody user −
[root@CentOS ~]$ ps -u nobody
PID TTY TIME CMD
1853 ? 00:00:00 dnsmasq
[root@CentOS ~]$查看 firewalld 进程的所有信息
To see all information about the firewalld process −
[root@CentOS ~]$ ps -wl -C firewalld
F S UID PID PPID C PRI NI ADDR SZ WCHAN TTY TIME CMD
0 S 0 762 1 0 80 0 - 81786 poll_s ? 00:00:01 firewalld
[root@CentOS ~]$让我们看看哪些进程消耗的内存最多
Let’s see which processes are consuming the most memory −
[root@CentOS ~]$ ps aux --sort=-pmem | head -10
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
cnetos 6130 0.7 5.7 1344512 108364 ? Sl 02:16 0:29 /usr/bin/gnome-shell
cnetos 6449 0.0 3.4 1375872 64440 ? Sl 02:16 0:00 /usr/libexec/evolution-calendar-factory
root 5404 0.6 2.1 190256 39920 tty1 Ssl+ 02:15 0:27 /usr/bin/Xorg :0 -background none -noreset -audit 4 -verbose -auth /run/gdm/auth-for-gdm-iDefCt/database -seat seat0 -nolisten tcp vt1
cnetos 6296 0.0 1.7 1081944 32136 ? Sl 02:16 0:00 /usr/libexec/evolution/3.12/evolution-alarm-notify
cnetos 6350 0.0 1.5 560728 29844 ? Sl 02:16 0:01 /usr/bin/prlsga
cnetos 6158 0.0 1.4 1026956 28004 ? Sl 02:16 0:00 /usr/libexec/gnome-shell-calendar-server
cnetos 6169 0.0 1.4 1120028 27576 ? Sl 02:16 0:00 /usr/libexec/evolution-source-registry
root 762 0.0 1.4 327144 26724 ? Ssl 02:09 0:01 /usr/bin/python -Es /usr/sbin/firewalld --nofork --nopid
cnetos 6026 0.0 1.4 1090832 26376 ? Sl 02:16 0:00 /usr/libexec/gnome-settings-daemon
[root@CentOS ~]$查看用户 centos 的所有进程，并格式化，显示自定义输出
See all the processes by user centos and format, displaying the custom output −
[cnetos@CentOS ~]$ ps -u cnetos -o pid,uname,comm
PID USER COMMAND
5802 centos gnome-keyring-d
5812 cnetos gnome-session
5819 cnetos dbus-launch
5820 cnetos dbus-daemon
5888 cnetos gvfsd
5893 cnetos gvfsd-fuse
5980 cnetos ssh-agent
5996 cnetos at-spi-bus-launpstree Command
pstree 与 ps 类似，但并不常用。它以更清晰的树状模式显示进程。
pstree is similar to ps but is not often used. It displays the processes in a neater tree fashion.
[centos@CentOS ~]$ pstree
systemd─┬─ModemManager───2*[{ModemManager}]
├─NetworkManager─┬─dhclient
│ └─2*[{NetworkManager}]
├─2*[abrt-watch-log]
├─abrtd
├─accounts-daemon───2*[{accounts-daemon}]
├─alsactl
├─at-spi-bus-laun─┬─dbus-daemon───{dbus-daemon}
│ └─3*[{at-spi-bus-laun}]
├─at-spi2-registr───2*[{at-spi2-registr}]
├─atd
├─auditd─┬─audispd─┬─sedispatch
│ │ └─{audispd}
│ └─{auditd}
├─avahi-daemon───avahi-daemon
├─caribou───2*[{caribou}]
├─cgrulesengd
├─chronyd
├─colord───2*[{colord}]
├─crond
├─cupsdpstree 的总输出可能超过 100 行。通常，ps 将提供更有用的信息。
The total output from pstree can exceed 100 lines. Usually, ps will give more useful information.
top Command
在解决 Linux 性能问题时， top 是最常用的命令之一。它适用于 Linux 中的实时统计和进程监控。以下是从命令行中调出时 top 的默认输出。
top is one of the most often used commands when troubleshooting performance issues in Linux. It is useful for real-time stats and process monitoring in Linux. Following is the default output of top when brought up from the command line.
Tasks: 170 total, 1 running, 169 sleeping, 0 stopped, 0 zombie
%Cpu(s): 2.3 us, 2.0 sy, 0.0 ni, 95.7 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
KiB Mem : 1879668 total, 177020 free, 607544 used, 1095104 buff/cache
KiB Swap: 3145724 total, 3145428 free, 296 used. 1034648 avail Mem
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
5404 root 20 0 197832 48024 6744 S 1.3 2.6 1:13.22 Xorg
8013 centos 20 0 555316 23104 13140 S 1.0 1.2 0:14.89 gnome-terminal-
6339 centos 20 0 332336 6016 3248 S 0.3 0.3 0:23.71 prlcc
6351 centos 20 0 21044 1532 1292 S 0.3 0.1 0:02.66 prlshprof在运行 top 时用到的常用热键（在 shell 中运行 top 时，按相应键即可访问热键）。
Common hot keys used while running top (hot keys are accessed by pressing the key as top is running in your shell).
Command |
Action |
b |
Enables / disables bold highlighting on top menu |
z |
Cycles the color scheme |
l |
Cycles the load average heading |
m |
Cycles the memory average heading |
t |
Task information heading |
h |
Help menu |
Shift+F |
Customizes sorting and display fields |
以下是 top 中的常用命令行开关。
Following are the common command line switches for top.
Command |
Action |
-o |
Sorts by column (can prepend with - or + to sort ascending or descending) |
-u |
Shows only processes from a specified user |
-d |
Updates the delay time of top |
-O |
Returns a list of columns which top can apply sorting |
top 中的排序选项屏幕，使用 Shift+F 呈现。此屏幕允许在 top 中对显示和排序选项进行自定义。
Sorting options screen in top, presented using Shift+F. This screen allows customization of top display and sort options.
Fields Management for window 1:Def, whose current sort field is %MEM
Navigate with Up/Dn, Right selects for move then <Enter> or Left commits,
'd' or <Space> toggles display, 's' sets sort. Use 'q' or <Esc> to end!
* PID = Process Id TGID = Thread Group Id
* USER = Effective User Name ENVIRON = Environment vars
* PR = Priority vMj = Major Faults delta
* NI = Nice Value vMn = Minor Faults delta
* VIRT = Virtual Image (KiB) USED = Res+Swap Size (KiB)
* RES = Resident Size (KiB) nsIPC = IPC namespace Inode
* SHR = Shared Memory (KiB) nsMNT = MNT namespace Inode
* S = Process Status nsNET = NET namespace Inode
* %CPU = CPU Usage nsPID = PID namespace Inode
* %MEM = Memory Usage (RES) nsUSER = USER namespace Inode
* TIME+ = CPU Time, hundredths nsUTS = UTS namespace Inode
* COMMAND = Command Name/Line
PPID = Parent Process pid
UID = Effective User Idtop，显示用户 rdc 的进程，并按内存使用量排序 −
top, showing the processes for user rdc and sorted by memory usage −
PID USER %MEM PR NI VIRT RES SHR S %CPU TIME+ COMMAND
6130 rdc 6.2 20 0 1349592 117160 33232 S 0.0 1:09.34 gnome-shell
6449 rdc 3.4 20 0 1375872 64428 21400 S 0.0 0:00.43 evolution-calen
6296 rdc 1.7 20 0 1081944 32140 22596 S 0.0 0:00.40 evolution-alarm
6350 rdc 1.6 20 0 560728 29844 4256 S 0.0 0:10.16 prlsga
6281 rdc 1.5 20 0 1027176 28808 17680 S 0.0 0:00.78 nautilus
6158 rdc 1.5 20 0 1026956 28004 19072 S 0.0 0:00.20 gnome-shell-cal显示有效的 top 字段（概览） −
Showing valid top fields (condensed) −
[centos@CentOS ~]$ top -O
PID
PPID
UID
USER
RUID
RUSER
SUID
SUSER
GID
GROUP
PGRP
TTY
TPGIDkill Command
kill 命令用于通过其 PID 从命令 shell 终止进程。终止进程时，我们需要指定要发送的信号。信号让内核了解我们希望如何结束进程。最常用的信号是 −
The kill command is used to kill a process from the command shell via its PID. When killing a process, we need to specify a signal to send. The signal lets the kernel know how we want to end the process. The most commonly used signals are −
-
SIGTERM is implied as the kernel lets a process know it should stop soon as it is safe to do so. SIGTERM gives the process an opportunity to exit gracefully and perform safe exit operations.
-
SIGHUP most daemons will restart when sent SIGHUP. This is often used on the processes when changes have been made to a configuration file.
-
SIGKILL since SIGTERM is the equivalent to asking a process to shut down. The kernel needs an option to end a process that will not comply with requests. When a process is hung, the SIGKILL option is used to shut the process down explicitly.
对于可以使用 kill 发送的所有信号列表，可以使用 -l 选项 −
For a list off all signals that can be sent with kill the -l option can be used −
[root@CentOS]# kill -l
1) SIGHUP 2) SIGINT 3) SIGQUIT 4) SIGILL 5) SIGTRAP
6) SIGABRT 7) SIGBUS 8) SIGFPE 9) SIGKILL 10) SIGUSR1
11) SIGSEGV 12) SIGUSR2 13) SIGPIPE 14) SIGALRM 15) SIGTERM
16) SIGSTKFLT 17) SIGCHLD 18) SIGCONT 19) SIGSTOP 20) SIGTSTP
21) SIGTTIN 22) SIGTTOU 23) SIGURG 24) SIGXCPU 25) SIGXFSZ
26) SIGVTALRM 27) SIGPROF 28) SIGWINCH 29) SIGIO 30) SIGPWR
31) SIGSYS 34) SIGRTMIN 35) SIGRTMIN+1 36) SIGRTMIN+2 37) SIGRTMIN+3
38) SIGRTMIN+4 39) SIGRTMIN+5 40) SIGRTMIN+6 41) SIGRTMIN+7 42) SIGRTMIN+8
43) SIGRTMIN+9 44) SIGRTMIN+10 45) SIGRTMIN+11 46) SIGRTMIN+12 47) SIGRTMIN+13
48) SIGRTMIN+14 49) SIGRTMIN+15 50) SIGRTMAX-14 51) SIGRTMAX-13 52) SIGRTMAX-12
53) SIGRTMAX-11 54) SIGRTMAX-10 55) SIGRTMAX-9 56) SIGRTMAX-8 57) SIGRTMAX-7
58) SIGRTMAX-6 59) SIGRTMAX-5 60) SIGRTMAX-4 61) SIGRTMAX-3 62) SIGRTMAX-2
63) SIGRTMAX-1 64) SIGRTMAX
[root@CentOS rdc]#使用 SIGHUP 来重启系统。
Using SIGHUP to restart system.
[root@CentOS]# pgrep systemd
1
464
500
643
15071
[root@CentOS]# kill -HUP 1
[root@CentOS]# pgrep systemd
1
464
500
643
15196
15197
15198
[root@CentOS]#pkill 允许管理员按进程名称发送 kill 信号。
pkill will allow the administrator to send a kill signal by the process name.
[root@CentOS]# pgrep ping
19450
[root@CentOS]# pkill -9 ping
[root@CentOS]# pgrep ping
[root@CentOS]#killall 将终止所有进程。小心以 root 身份使用 killall，因为它会终止所有用户的进程。
killall will kill all the processes. Be careful using killall as root, as it will kill all the processes for all users.
[root@CentOS]# killall chromefree Command
free 是一个非常简单的命令，通常用于快速查看系统的内存。它显示已使用的物理内存和交换内存的总量。
free is a pretty simple command often used to quickly check the memory of a system. It displays the total amount of used physical and swap memory.
[root@CentOS]# free
total used free shared buff/cache available
Mem: 1879668 526284 699796 10304 653588 1141412
Swap: 3145724 0 3145724
[root@CentOS]#nice Command
nice 允许管理员根据 CPU 使用情况设置进程的调度优先级。基本上，niceness 是内核将如何为进程或作业调度 CPU 时间片的。默认情况下，假定进程对 CPU 资源的访问权相同。
nice will allow an administrator to set the scheduling priority of a process in terms of CPU usages. The niceness is basically how the kernel will schedule CPU time slices for a process or job. By default, it is assumed the process is given equal access to CPU resources.
首先，让我们使用 top 查看当前正在运行的进程的优先级。
First, let’s use top to check the niceness of the currently running processes.
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
28 root 39 19 0 0 0 S 0.0 0.0 0:00.17 khugepaged
690 root 39 19 16808 1396 1164 S 0.0 0.1 0:00.01 alsactl]
9598 rdc 39 19 980596 21904 10284 S 0.0 1.2 0:00.27 tracker-extract
9599 rdc 39 19 469876 9608 6980 S 0.0 0.5 0:00.04 tracker-miner-a
9609 rdc 39 19 636528 13172 8044 S 0.0 0.7 0:00.12 tracker-miner-f
9611 rdc 39 19 469620 8984 6496 S 0.0 0.5 0:00.02 tracker-miner-u
27 root 25 5 0 0 0 S 0.0 0.0 0:00.00 ksmd
637 rtkit 21 1 164648 1276 1068 S 0.0 0.1 0:00.11 rtkit-daemon
1 root 20 0 128096 6712 3964 S 0.3 0.4 0:03.57 systemd
2 root 20 0 0 0 0 S 0.0 0.0 0:00.01 kthreadd
3 root 20 0 0 0 0 S 0.0 0.0 0:00.50 ksoftirqd/0
7 root 20 0 0 0 0 S 0.0 0.0 0:00.00 migration/0
8 root 20 0 0 0 0 S 0.0 0.0 0:00.00 rcu_bh
9 root 20 0 0 0 0 S 0.0 0.0 0:02.07 rcu_sched我们希望关注 NI 所描绘的 NICE 列。niceness 范围可以在 -20 到正 19 之间。-20 表示给予的最高优先级。
We want to focus on the NICE column depicted by NI. The niceness range can be anywhere between -20 to positive 19. -20 represents the highest given priority.
nohup nice --20 ping www.google.com &PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
30727 root 0 -20 132108 1640 1264 S 0.0 0.1 0:00.06 ping