Linux - 进程
通过ps仔细观察一下linux的进程。
ps
a: all;x: 只显示有tty的process，一般和all连用;j:job，相当于多显示几列信息，把sid，tty之类的都显示出来；f:forest，层级显示。用这个去发现父进程、同一session下的进程，很形象。
打开yakuake，里面开启一个使用zsh的终端pts/0，然后在里面执行前后台两个命令，每个命令都是由管道连接的两个命令：
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~ ping localhost -aq | grep icmp &
[1] 5989 5990
~ ping localhost -aq | grep icmp
然后在yakuake里再打开一个使用zsh的终端pts/1，查看所有终端0的进程：
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~ % ps axj | grep pts/0
PPID PID PGID SID TTY TPGID STAT UID TIME COMMAND
1626 3564 3564 3564 pts/0 7887 Ss 1000 0:00 /usr/bin/zsh
3564 5989 5989 3564 pts/0 7887 SN 1000 0:00 ping localhost -aq
3564 5990 5989 3564 pts/0 7887 SN 1000 0:00 grep --color=auto --exclude-dir=.bzr --exclude-dir=CVS --exclude-dir=.git --exclude-dir=.hg --exclude-dir=.svn --exclude-dir=.idea --exclude-dir=.tox icmp
3564 7887 7887 3564 pts/0 7887 S+ 1000 0:00 ping localhost -aq
3564 7888 7887 3564 pts/0 7887 S+ 1000 0:00 grep --color=auto --exclude-dir=.bzr --exclude-dir=CVS --exclude-dir=.git --exclude-dir=.hg --exclude-dir=.svn --exclude-dir=.idea --exclude-dir=.tox icmp
- PID：process id；
- PPID：parent process id；
- PGID： process group id；
- SID：session id；
- TPGID：tty process group id，
tty + PGID； - TTY：teletypewriter，电传打字机；
PPID - 判断进程fork关系
无论是ping还是grep，都是在zsh里执行的，所以他们的父进程都是zsh（PID=3564），所以他们的PPID=3564。
PGID - 判断进程组
shell里的每个进程都属于一个进程组。注意是“shell里的每个进程”。如果内核支持_POSIX_JOB_CONTROL（该宏被定义）则内核会为Shell上的每一条命令行（可能由多个命令通过管道等连接）创建一个进程组。从这点上看，进程组不是进程的概念，而是shell上才有，所以在task_struct里并没有存储进程组id之类的变量。
进程组是为了方便管理进程，信号发给进程组，相当于发给进程组的所有进程。
后台ping和后台grep用管道连接，PGID都是ping的PID=5989，所以后台ping和后台grep 属于同一个进程组（PGID相同），组长的PGID=PID，所以组长是第一个命令ping。
前台ping和前台grep同理，也属于同一个进程组。
SID - 判断是否属于同一个TTY
会话ID。一般一个用户登录后新建一个会话，可以理解为一个tty。登录后的第一个进程叫做会话领头进程（session leader），通常是一个shell/bash。对于会话领头进程，其PID=SID。而我是使用zsh的，所以第一个SID都是zsh的PID。
TPGID - 判断前后台进程
当前TTY的PGID。一个TTY只能有一个前台进程，所以这个前台进程的组长id，即为TTY的PGID。所以TPGID就是该会话的前台进程的进程组组长ID。
所以所有PGID≠TPGID的进程，都是后台进程。否则都为前台进程。
没有TTY的进程，TTY为?，TPGID都为-1。
STAT
上面判断是否是前台进程判断了半天，其实不如直接看STAT。它的含义可以直接man ps找到解释：
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PROCESS STATE CODES
Here are the different values that the s, stat and state output specifiers (header "STAT" or "S") will display
to describe the state of a process:
D uninterruptible sleep (usually IO)
I Idle kernel thread
R running or runnable (on run queue)
S interruptible sleep (waiting for an event to complete)
T stopped by job control signal
t stopped by debugger during the tracing
W paging (not valid since the 2.6.xx kernel)
X dead (should never be seen)
Z defunct ("zombie") process, terminated but not reaped by its parent
For BSD formats and when the stat keyword is used, additional characters may be displayed:
< high-priority (not nice to other users)
N low-priority (nice to other users)
L has pages locked into memory (for real-time and custom IO)
s is a session leader
l is multi-threaded (using CLONE_THREAD, like NPTL pthreads do)
+ is in the foreground process group
+就是前台进程。不用比较TPGID是否等于PGID了；s就是session leader。不用比较PID是否等于SID了；
f - forest
层级显示，可以很容易看出来哪些进程是同一个会话的，进程间的继承关系是什么，再叠加STAT，可以找出来session leader和foreground process。唯一不能直接看出来的是进程组，需要观察一下PGID。
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~ % ps axjf
PPID PID PGID SID TTY TPGID STAT UID TIME COMMAND
1 1626 1625 1625 ? -1 Sl 1000 0:17 /usr/bin/yakuake
1626 3564 3564 3564 pts/0 7887 Ss 1000 0:00 \_ /usr/bin/zsh
3564 5989 5989 3564 pts/0 7887 SN 1000 0:00 | \_ ping localhost -aq
3564 5990 5989 3564 pts/0 7887 SN 1000 0:00 | \_ grep --color=auto --exclude-dir=.bzr --exclude-dir=CVS --exclude-dir=.git --exclude-dir=.hg --exclude-dir=.svn --
3564 7887 7887 3564 pts/0 7887 S+ 1000 0:00 | \_ ping localhost -aq
3564 7888 7887 3564 pts/0 7887 S+ 1000 0:00 | \_ grep --color=auto --exclude-dir=.bzr --exclude-dir=CVS --exclude-dir=.git --exclude-dir=.hg --exclude-dir=.svn --
1626 5995 5995 5995 pts/2 8675 Ss 1000 0:00 \_ /usr/bin/zsh
5995 8675 8675 5995 pts/2 8675 R+ 1000 0:00 \_ ps axjf
系统process总览
最后总览一下Debian + KDE的所有进程表：
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~ % ps axjf
PPID PID PGID SID TTY TPGID STAT UID TIME COMMAND
0 2 0 0 ? -1 S 0 0:00 [kthreadd]
2 3 0 0 ? -1 I< 0 0:00 \_ [rcu_gp]
2 4 0 0 ? -1 I< 0 0:00 \_ [rcu_par_gp]
2 6 0 0 ? -1 I< 0 0:00 \_ [kworker/0:0H-events_highpri]
2 9 0 0 ? -1 I< 0 0:00 \_ [mm_percpu_wq]
2 10 0 0 ? -1 S 0 0:00 \_ [rcu_tasks_rude_]
2 11 0 0 ? -1 S 0 0:00 \_ [rcu_tasks_trace]
2 12 0 0 ? -1 S 0 0:00 \_ [ksoftirqd/0]
2 13 0 0 ? -1 I 0 0:07 \_ [rcu_sched]
2 14 0 0 ? -1 S 0 0:00 \_ [migration/0]
2 15 0 0 ? -1 S 0 0:00 \_ [cpuhp/0]
2 16 0 0 ? -1 S 0 0:00 \_ [cpuhp/1]
2 17 0 0 ? -1 S 0 0:00 \_ [migration/1]
2 18 0 0 ? -1 S 0 0:00 \_ [ksoftirqd/1]
2 20 0 0 ? -1 I< 0 0:00 \_ [kworker/1:0H-events_highpri]
2 21 0 0 ? -1 S 0 0:00 \_ [cpuhp/2]
2 22 0 0 ? -1 S 0 0:00 \_ [migration/2]
2 23 0 0 ? -1 S 0 0:00 \_ [ksoftirqd/2]
2 25 0 0 ? -1 I< 0 0:00 \_ [kworker/2:0H-events_highpri]
2 26 0 0 ? -1 S 0 0:00 \_ [cpuhp/3]
2 27 0 0 ? -1 S 0 0:00 \_ [migration/3]
2 28 0 0 ? -1 S 0 0:00 \_ [ksoftirqd/3]
2 30 0 0 ? -1 I< 0 0:00 \_ [kworker/3:0H-events_highpri]
2 31 0 0 ? -1 S 0 0:00 \_ [cpuhp/4]
2 32 0 0 ? -1 S 0 0:00 \_ [migration/4]
2 33 0 0 ? -1 S 0 0:00 \_ [ksoftirqd/4]
2 35 0 0 ? -1 I< 0 0:00 \_ [kworker/4:0H-events_highpri]
2 36 0 0 ? -1 S 0 0:00 \_ [cpuhp/5]
2 37 0 0 ? -1 S 0 0:00 \_ [migration/5]
2 38 0 0 ? -1 S 0 0:00 \_ [ksoftirqd/5]
2 40 0 0 ? -1 I< 0 0:00 \_ [kworker/5:0H-events_highpri]
2 41 0 0 ? -1 S 0 0:00 \_ [cpuhp/6]
2 42 0 0 ? -1 S 0 0:00 \_ [migration/6]
2 43 0 0 ? -1 S 0 0:00 \_ [ksoftirqd/6]
2 45 0 0 ? -1 I< 0 0:00 \_ [kworker/6:0H-events_highpri]
2 46 0 0 ? -1 S 0 0:00 \_ [cpuhp/7]
2 47 0 0 ? -1 S 0 0:00 \_ [migration/7]
2 48 0 0 ? -1 S 0 0:00 \_ [ksoftirqd/7]
2 50 0 0 ? -1 I< 0 0:00 \_ [kworker/7:0H-events_highpri]
2 59 0 0 ? -1 S 0 0:00 \_ [kdevtmpfs]
2 60 0 0 ? -1 I< 0 0:00 \_ [netns]
2 61 0 0 ? -1 S 0 0:00 \_ [kauditd]
2 62 0 0 ? -1 S 0 0:00 \_ [khungtaskd]
2 63 0 0 ? -1 S 0 0:00 \_ [oom_reaper]
2 64 0 0 ? -1 I< 0 0:00 \_ [writeback]
2 65 0 0 ? -1 S 0 0:00 \_ [kcompactd0]
2 66 0 0 ? -1 SN 0 0:00 \_ [ksmd]
2 67 0 0 ? -1 SN 0 0:00 \_ [khugepaged]
2 87 0 0 ? -1 I< 0 0:00 \_ [kintegrityd]
2 88 0 0 ? -1 I< 0 0:00 \_ [kblockd]
2 89 0 0 ? -1 I< 0 0:00 \_ [blkcg_punt_bio]
2 92 0 0 ? -1 I< 0 0:00 \_ [edac-poller]
2 93 0 0 ? -1 I< 0 0:00 \_ [devfreq_wq]
2 94 0 0 ? -1 I< 0 0:00 \_ [kworker/6:1H-events_highpri]
2 98 0 0 ? -1 S 0 0:00 \_ [kswapd0]
2 99 0 0 ? -1 I< 0 0:00 \_ [kthrotld]
2 100 0 0 ? -1 S 0 0:00 \_ [irq/123-aerdrv]
2 101 0 0 ? -1 S 0 0:00 \_ [irq/124-aerdrv]
2 102 0 0 ? -1 S 0 0:00 \_ [irq/125-aerdrv]
2 103 0 0 ? -1 I< 0 0:00 \_ [acpi_thermal_pm]
2 105 0 0 ? -1 I< 0 0:00 \_ [kworker/1:1H-kblockd]
2 106 0 0 ? -1 I< 0 0:00 \_ [ipv6_addrconf]
2 115 0 0 ? -1 I< 0 0:00 \_ [kstrp]
2 118 0 0 ? -1 I< 0 0:00 \_ [zswap-shrink]
2 141 0 0 ? -1 I< 0 0:00 \_ [kworker/5:1H-events_highpri]
2 173 0 0 ? -1 I< 0 0:00 \_ [kworker/0:1H-kblockd]
2 181 0 0 ? -1 S 0 0:34 \_ [irq/126-ELAN101]
2 184 0 0 ? -1 I 0 0:00 \_ [kworker/4:2-events]
2 185 0 0 ? -1 I< 0 0:00 \_ [ata_sff]
2 186 0 0 ? -1 I< 0 0:00 \_ [nvme-wq]
2 187 0 0 ? -1 I< 0 0:00 \_ [nvme-reset-wq]
2 188 0 0 ? -1 I< 0 0:00 \_ [nvme-delete-wq]
2 189 0 0 ? -1 S 0 0:00 \_ [scsi_eh_0]
2 190 0 0 ? -1 I< 0 0:00 \_ [scsi_tmf_0]
2 191 0 0 ? -1 S 0 0:00 \_ [scsi_eh_1]
2 192 0 0 ? -1 I< 0 0:00 \_ [scsi_tmf_1]
2 193 0 0 ? -1 S 0 0:00 \_ [scsi_eh_2]
2 194 0 0 ? -1 I< 0 0:00 \_ [scsi_tmf_2]
2 196 0 0 ? -1 I< 0 0:00 \_ [kworker/2:1H-events_highpri]
2 197 0 0 ? -1 S 0 0:00 \_ [card0-crtc0]
2 198 0 0 ? -1 S 0 0:00 \_ [card0-crtc1]
2 199 0 0 ? -1 S 0 0:00 \_ [card0-crtc2]
2 201 0 0 ? -1 I< 0 0:00 \_ [kworker/3:1H-events_highpri]
2 202 0 0 ? -1 I< 0 0:00 \_ [kworker/7:1H-events_highpri]
2 204 0 0 ? -1 I< 0 0:00 \_ [kworker/4:1H-events_highpri]
2 207 0 0 ? -1 I< 0 0:00 \_ [md]
2 218 0 0 ? -1 I< 0 0:00 \_ [raid5wq]
2 260 0 0 ? -1 S 0 0:00 \_ [jbd2/nvme0n1p5-]
2 261 0 0 ? -1 I< 0 0:00 \_ [ext4-rsv-conver]
2 366 0 0 ? -1 I< 0 0:00 \_ [tpm_dev_wq]
2 376 0 0 ? -1 S 0 0:00 \_ [irq/139-mei_me]
2 385 0 0 ? -1 I< 0 0:00 \_ [kmemstick]
2 386 0 0 ? -1 S 0 0:00 \_ [watchdogd]
2 457 0 0 ? -1 I< 0 0:00 \_ [cryptd]
2 459 0 0 ? -1 I< 0 0:00 \_ [cfg80211]
2 477 0 0 ? -1 S 0 0:04 \_ [irq/141-iwlwifi]
2 542 0 0 ? -1 I 0 0:00 \_ [kworker/0:2-events]
2 587 0 0 ? -1 S 0 0:00 \_ [jbd2/sda4-8]
2 588 0 0 ? -1 I< 0 0:00 \_ [ext4-rsv-conver]
2 595 0 0 ? -1 S 0 0:00 \_ [jbd2/sda3-8]
2 596 0 0 ? -1 I< 0 0:00 \_ [ext4-rsv-conver]
2 1766 0 0 ? -1 S< 0 0:00 \_ [krfcommd]
2 5507 0 0 ? -1 I 0 0:00 \_ [kworker/7:0-mm_percpu_wq]
2 6015 0 0 ? -1 I 0 0:01 \_ [kworker/u16:1-i915]
2 6409 0 0 ? -1 I 0 0:00 \_ [kworker/0:1-cgroup_destroy]
2 6711 0 0 ? -1 I 0 0:00 \_ [kworker/1:0-cgroup_destroy]
2 6822 0 0 ? -1 I 0 0:00 \_ [kworker/5:3-events]
2 7438 0 0 ? -1 I 0 0:00 \_ [kworker/3:2-events]
2 7579 0 0 ? -1 I 0 0:00 \_ [kworker/6:2-mm_percpu_wq]
2 7637 0 0 ? -1 I< 0 0:00 \_ [kworker/u17:1-rb_allocator]
2 7681 0 0 ? -1 I 0 0:00 \_ [kworker/7:2-cgroup_destroy]
2 7685 0 0 ? -1 I 0 0:00 \_ [kworker/5:1-mm_percpu_wq]
2 7760 0 0 ? -1 I 0 0:02 \_ [kworker/2:3-events]
2 7858 0 0 ? -1 I 0 0:00 \_ [kworker/u16:2-events_unbound]
2 7882 0 0 ? -1 I 0 0:00 \_ [kworker/4:0-events]
2 7884 0 0 ? -1 I 0 0:00 \_ [kworker/6:0-events]
2 7893 0 0 ? -1 I 0 0:00 \_ [kworker/u16:3-flush-259:0]
2 8518 0 0 ? -1 I 0 0:00 \_ [kworker/2:1-events]
2 8553 0 0 ? -1 D< 0 0:00 \_ [kworker/u17:2+i915_flip]
2 8562 0 0 ? -1 I 0 0:00 \_ [kworker/1:1-events]
2 8564 0 0 ? -1 I 0 0:00 \_ [kworker/3:3-events]
2 8629 0 0 ? -1 I 0 0:00 \_ [kworker/6:1]
2 8630 0 0 ? -1 I 0 0:00 \_ [kworker/4:1-events]
2 8631 0 0 ? -1 I 0 0:00 \_ [kworker/4:3-mm_percpu_wq]
2 8636 0 0 ? -1 I 0 0:00 \_ [kworker/u16:0-events_unbound]
2 8637 0 0 ? -1 I 0 0:00 \_ [kworker/7:1]
2 8673 0 0 ? -1 I 0 0:00 \_ [kworker/0:0-events]
0 1 1 1 ? -1 Ss 0 0:02 /sbin/init
1 308 308 308 ? -1 Ss 0 0:01 /lib/systemd/systemd-journald
1 324 324 324 ? -1 Ss 0 0:00 /lib/systemd/systemd-udevd
1 624 624 624 ? -1 Ssl 101 0:00 /lib/systemd/systemd-timesyncd
1 631 631 631 ? -1 Ss 0 0:00 /usr/sbin/haveged --Foreground --verbose=1
1 634 634 634 ? -1 Ssl 0 0:00 /usr/libexec/accounts-daemon
1 636 636 636 ? -1 Ss 112 0:00 avahi-daemon: running [linux.local]
636 640 636 636 ? -1 S 112 0:00 \_ avahi-daemon: chroot helper
1 637 637 637 ? -1 Ss 0 0:00 /usr/libexec/bluetooth/bluetoothd
1 638 638 638 ? -1 Ss 0 0:00 /usr/sbin/cron -f
1 639 639 639 ? -1 Ss 105 0:03 /usr/bin/dbus-daemon --system --address=systemd: --nofork --nopidfile --systemd-activation --syslog-only
1 641 641 641 ? -1 Ssl 0 0:04 /usr/sbin/NetworkManager --no-daemon
1 646 646 646 ? -1 Ssl 0 0:00 /usr/libexec/polkitd --no-debug
1 647 647 647 ? -1 Ssl 0 0:00 /usr/sbin/rsyslogd -n -iNONE
1 648 648 648 ? -1 Ss 0 0:00 /usr/sbin/smartd -n
1 652 652 652 ? -1 Ss 0 0:00 /lib/systemd/systemd-logind
1 653 653 653 ? -1 Ssl 0 0:00 /usr/libexec/udisks2/udisksd
1 654 654 654 ? -1 Ss 0 0:00 /sbin/wpa_supplicant -u -s -O /run/wpa_supplicant
1 672 672 672 ? -1 Ssl 0 0:00 /usr/sbin/ModemManager
1 817 817 817 ? -1 Ss 0 0:00 /usr/sbin/cupsd -l
1 821 821 821 ? -1 Ssl 0 0:00 /usr/bin/python3 /usr/share/unattended-upgrades/unattended-upgrade-shutdown --wait-for-signal
1 822 822 822 ? -1 Ssl 0 0:14 /usr/bin/containerd
1 825 825 825 ? -1 Ssl 0 0:00 /usr/bin/sddm
825 839 839 839 tty7 839 Ssl+ 0 3:27 \_ /usr/lib/xorg/Xorg -nolisten tcp -auth /var/run/sddm/{f3928438-0f85-4350-8dbe-b568f505d2ab} -background none -noreset
825 1356 825 825 ? -1 S 0 0:00 \_ /usr/lib/x86_64-linux-gnu/sddm/sddm-helper --socket /tmp/sddm-auth16984d6f-4fb6-4c5e-a75a-cb3d4fdc13bb --id 1 --start
1356 1388 825 825 ? -1 Sl 1000 0:00 \_ /usr/bin/startplasma-x11
1388 1438 1438 1438 ? -1 Ss 1000 0:00 \_ /usr/bin/ssh-agent /usr/bin/im-launch /usr/bin/startplasma-x11
1 826 826 826 ? -1 Ss 0 0:00 sshd: /usr/sbin/sshd -D [listener] 0 of 10-100 startups
1 828 828 828 ? -1 Ssl 0 0:00 /usr/sbin/cups-browsed
1 891 891 891 ? -1 SNsl 110 0:00 /usr/libexec/rtkit-daemon
1 920 920 920 ? -1 Ssl 0 0:02 /usr/bin/dockerd -H fd:// --containerd=/run/containerd/containerd.sock
1 1183 1183 1183 ? -1 Ss 106 0:00 /usr/sbin/exim4 -bd -q30m
1 1358 1358 1358 ? -1 Ss 1000 0:00 /lib/systemd/systemd --user
1358 1359 1358 1358 ? -1 S 1000 0:00 \_ (sd-pam)
1358 1378 1378 1378 ? -1 S<sl 1000 0:00 \_ /usr/bin/pipewire
1378 1384 1378 1378 ? -1 S<l 1000 0:00 | \_ /usr/bin/pipewire-media-session
1358 1379 1379 1379 ? -1 S<sl 1000 0:26 \_ /usr/bin/pulseaudio --daemonize=no --log-target=journal
1379 1459 1379 1379 ? -1 Sl 1000 0:00 | \_ /usr/libexec/pulse/gsettings-helper
1358 1382 1382 1382 ? -1 Ss 1000 0:02 \_ /usr/bin/dbus-daemon --session --address=systemd: --nofork --nopidfile --systemd-activation --syslog-only
1358 1540 1382 1382 ? -1 Sl 1000 0:01 \_ /usr/lib/x86_64-linux-gnu/libexec/kactivitymanagerd
1358 1546 1546 1546 ? -1 Ssl 1000 0:01 \_ /usr/bin/kglobalaccel5
1358 1585 1382 1382 ? -1 Sl 1000 0:00 \_ /usr/libexec/dconf-service
1358 1713 1382 1382 ? -1 Sl 1000 0:01 \_ /usr/lib/x86_64-linux-gnu/libexec/kf5/kscreen_backend_launcher
1358 1718 1382 1382 ? -1 Sl 1000 0:05 \_ /usr/bin/ksystemstats
1718 1720 1382 1382 ? -1 S 1000 0:06 | \_ /usr/bin/ksysguardd
1358 1762 1762 1762 ? -1 Ss 1000 0:00 \_ /usr/libexec/bluetooth/obexd
1358 7897 1382 1382 ? -1 Sl 1000 0:00 \_ /usr/bin/krunner
1 1387 1386 1386 ? -1 Sl 1000 0:01 /usr/bin/kwalletd5 --pam-login 7 3
1 1449 1448 1448 ? -1 S 1000 0:06 /usr/bin/fcitx -d
1 1455 1455 1455 ? -1 Ss 1000 0:01 /usr/bin/dbus-daemon --syslog --fork --print-pid 5 --print-address 7 --config-file /usr/share/fcitx/dbus/daemon.conf
1 1481 825 825 ? -1 S 1000 0:00 /usr/lib/x86_64-linux-gnu/libexec/kf5/start_kdeinit
1 1486 1486 1486 ? -1 Ss 1000 0:00 kdeinit5: Running...
1486 1488 1486 1486 ? -1 Sl 1000 0:01 \_ /usr/lib/x86_64-linux-gnu/libexec/kf5/klauncher --fd=9
1486 2618 1486 1486 ? -1 S 1000 0:00 \_ file.so [kdeinit5] file local:/run/user/1000/klauncherNRjbkV.1.slave-socket local:/run/user/1000/kded5AVLYwh.1.slave-
1486 2619 1486 1486 ? -1 S 1000 0:00 \_ file.so [kdeinit5] file local:/run/user/1000/klauncherNRjbkV.1.slave-socket local:/run/user/1000/kded5QHbsdh.2.slave-
1 1499 1498 1498 ? -1 SN 1000 0:00 /usr/bin/fcitx-dbus-watcher unix:abstract=/tmp/dbus-fTAHPklDfF,guid=ef338b2fb2f5d014c3f9d9226180eda6 1455
1 1512 1511 1511 ? -1 Sl 1000 0:05 /usr/bin/kded5
1 1518 1517 1517 ? -1 Sl 1000 4:22 /usr/bin/kwin_x11
1 1549 1548 1548 ? -1 Sl 1000 0:01 /usr/bin/ksmserver
1 1554 1553 1553 ? -1 Sl 1000 2:18 /usr/bin/plasmashell
1554 7909 1553 1553 ? -1 Sl 1000 0:21 \_ /opt/google/chrome/chrome --enable-crashpad
7909 7915 1553 1553 ? -1 S 1000 0:00 \_ cat
7909 7916 1553 1553 ? -1 S 1000 0:00 \_ cat
7909 7926 1553 1553 ? -1 S 1000 0:00 \_ /opt/google/chrome/chrome --type=zygote --no-zygote-sandbox --enable-crashpad --crashpad-handler-pid=7918 --enabl
7926 7951 1553 1553 ? -1 Sl 1000 0:08 | \_ /opt/google/chrome/chrome --type=gpu-process --field-trial-handle=9298843108180127399,16641463171786290886,13
7909 7927 1553 1553 ? -1 S 1000 0:00 \_ /opt/google/chrome/chrome --type=zygote --enable-crashpad --crashpad-handler-pid=7918 --enable-crash-reporter=355
7927 7928 1553 1553 ? -1 S 1000 0:00 | \_ /opt/google/chrome/nacl_helper
7927 7931 1553 1553 ? -1 S 1000 0:00 | \_ /opt/google/chrome/chrome --type=zygote --enable-crashpad --crashpad-handler-pid=7918 --enable-crash-reporter
7931 7954 1553 1553 ? -1 Sl 1000 0:00 | \_ /opt/google/chrome/chrome --type=utility --utility-sub-type=storage.mojom.StorageService --field-trial-ha
7931 8037 1553 1553 ? -1 Sl 1000 0:00 | \_ /opt/google/chrome/chrome --type=renderer --enable-crashpad --crashpad-handler-pid=7918 --enable-crash-re
7931 8051 1553 1553 ? -1 Sl 1000 0:00 | \_ /opt/google/chrome/chrome --type=utility --utility-sub-type=proxy_resolver.mojom.ProxyResolverFactory --f
7931 8056 1553 1553 ? -1 Sl 1000 0:06 | \_ /opt/google/chrome/chrome --type=renderer --enable-crashpad --crashpad-handler-pid=7918 --enable-crash-re
7931 8072 1553 1553 ? -1 Sl 1000 0:00 | \_ /opt/google/chrome/chrome --type=renderer --enable-crashpad --crashpad-handler-pid=7918 --enable-crash-re
7931 8077 1553 1553 ? -1 Sl 1000 0:00 | \_ /opt/google/chrome/chrome --type=renderer --enable-crashpad --crashpad-handler-pid=7918 --enable-crash-re
7931 8098 1553 1553 ? -1 Sl 1000 0:00 | \_ /opt/google/chrome/chrome --type=renderer --enable-crashpad --crashpad-handler-pid=7918 --enable-crash-re
7931 8104 1553 1553 ? -1 Sl 1000 0:00 | \_ /opt/google/chrome/chrome --type=renderer --enable-crashpad --crashpad-handler-pid=7918 --enable-crash-re
7931 8117 1553 1553 ? -1 Sl 1000 0:01 | \_ /opt/google/chrome/chrome --type=renderer --enable-crashpad --crashpad-handler-pid=7918 --enable-crash-re
7931 8125 1553 1553 ? -1 Sl 1000 0:00 | \_ /opt/google/chrome/chrome --type=renderer --enable-crashpad --crashpad-handler-pid=7918 --enable-crash-re
7931 8150 1553 1553 ? -1 Sl 1000 0:00 | \_ /opt/google/chrome/chrome --type=renderer --enable-crashpad --crashpad-handler-pid=7918 --enable-crash-re
7931 8156 1553 1553 ? -1 Sl 1000 0:00 | \_ /opt/google/chrome/chrome --type=renderer --enable-crashpad --crashpad-handler-pid=7918 --enable-crash-re
7931 8175 1553 1553 ? -1 Sl 1000 0:07 | \_ /opt/google/chrome/chrome --type=renderer --enable-crashpad --crashpad-handler-pid=7918 --enable-crash-re
7931 8184 1553 1553 ? -1 Sl 1000 0:00 | \_ /opt/google/chrome/chrome --type=renderer --enable-crashpad --crashpad-handler-pid=7918 --enable-crash-re
7931 8198 1553 1553 ? -1 Sl 1000 0:00 | \_ /opt/google/chrome/chrome --type=renderer --enable-crashpad --crashpad-handler-pid=7918 --enable-crash-re
7931 8211 1553 1553 ? -1 Sl 1000 0:00 | \_ /opt/google/chrome/chrome --type=renderer --enable-crashpad --crashpad-handler-pid=7918 --enable-crash-re
7931 8225 1553 1553 ? -1 Sl 1000 0:00 | \_ /opt/google/chrome/chrome --type=renderer --enable-crashpad --crashpad-handler-pid=7918 --enable-crash-re
7931 8238 1553 1553 ? -1 Sl 1000 0:02 | \_ /opt/google/chrome/chrome --type=renderer --enable-crashpad --crashpad-handler-pid=7918 --enable-crash-re
7931 8274 1553 1553 ? -1 Sl 1000 0:44 | \_ /opt/google/chrome/chrome --type=renderer --enable-crashpad --crashpad-handler-pid=7918 --enable-crash-re
7931 8456 1553 1553 ? -1 Sl 1000 0:00 | \_ /opt/google/chrome/chrome --type=renderer --enable-crashpad --crashpad-handler-pid=7918 --enable-crash-re
7931 8475 1553 1553 ? -1 Sl 1000 0:00 | \_ /opt/google/chrome/chrome --type=renderer --enable-crashpad --crashpad-handler-pid=7918 --enable-crash-re
7909 7952 1553 1553 ? -1 Sl 1000 0:02 \_ /opt/google/chrome/chrome --type=utility --utility-sub-type=network.mojom.NetworkService --field-trial-handle=929
1 1560 1559 1559 ? -1 Sl 1000 0:01 /usr/bin/kaccess
1 1562 1561 1561 ? -1 Sl 1000 0:00 /usr/lib/x86_64-linux-gnu/libexec/polkit-kde-authentication-agent-1
1 1564 1563 1563 ? -1 Sl 1000 0:00 /usr/bin/xembedsniproxy
1 1594 1593 1593 ? -1 Sl 1000 0:01 /usr/lib/x86_64-linux-gnu/libexec/kdeconnectd
1 1596 1595 1595 ? -1 Sl 1000 0:01 /usr/lib/x86_64-linux-gnu/libexec/DiscoverNotifier
1 1603 1602 1602 ? -1 Sl 1000 0:00 /usr/bin/gmenudbusmenuproxy
1 1615 1614 1614 ? -1 Sl 1000 0:00 /usr/libexec/geoclue-2.0/demos/agent
1 1617 1616 1616 ? -1 Sl 1000 0:01 /usr/bin/korgac
1 1622 1621 1621 ? -1 Sl 1000 0:01 /usr/lib/x86_64-linux-gnu/libexec/org_kde_powerdevil
1 1624 1623 1623 ? -1 Sl 1000 0:00 /usr/libexec/at-spi-bus-launcher --launch-immediately
1624 1633 1623 1623 ? -1 S 1000 0:00 \_ /usr/bin/dbus-daemon --config-file=/usr/share/defaults/at-spi2/accessibility.conf --nofork --print-address 3
1 1626 1625 1625 ? -1 Sl 1000 0:17 /usr/bin/yakuake
1626 3564 3564 3564 pts/0 7887 Ss 1000 0:00 \_ /usr/bin/zsh
3564 5989 5989 3564 pts/0 7887 SN 1000 0:00 | \_ ping localhost -aq
3564 5990 5989 3564 pts/0 7887 SN 1000 0:00 | \_ grep --color=auto --exclude-dir=.bzr --exclude-dir=CVS --exclude-dir=.git --exclude-dir=.hg --exclude-dir=.svn --
3564 7887 7887 3564 pts/0 7887 S+ 1000 0:00 | \_ ping localhost -aq
3564 7888 7887 3564 pts/0 7887 S+ 1000 0:00 | \_ grep --color=auto --exclude-dir=.bzr --exclude-dir=CVS --exclude-dir=.git --exclude-dir=.hg --exclude-dir=.svn --
1626 5995 5995 5995 pts/2 8675 Ss 1000 0:00 \_ /usr/bin/zsh
5995 8675 8675 5995 pts/2 8675 R+ 1000 0:00 \_ ps axjf
1 1650 1650 1650 ? -1 Ssl 0 0:03 /usr/libexec/packagekitd
1 1654 1654 1654 ? -1 Ssl 0 0:00 /usr/libexec/upowerd
1 1697 1696 1696 ? -1 Sl 1000 0:01 /usr/bin/akonadi_control
1697 1702 1696 1696 ? -1 Sl 1000 0:00 \_ /usr/bin/akonadiserver
1702 1725 1696 1696 ? -1 Sl 1000 0:01 | \_ /usr/sbin/mysqld --defaults-file=/home/pichu/.local/share/akonadi/mysql.conf --datadir=/home/pichu/.local/share/a
1697 1779 1696 1696 ? -1 Sl 1000 0:01 \_ /usr/bin/akonadi_akonotes_resource --identifier akonadi_akonotes_resource_0
1697 1780 1696 1696 ? -1 SLl 1000 0:01 \_ /usr/bin/akonadi_archivemail_agent --identifier akonadi_archivemail_agent
1697 1781 1696 1696 ? -1 Sl 1000 0:01 \_ /usr/bin/akonadi_birthdays_resource --identifier akonadi_birthdays_resource
1697 1782 1696 1696 ? -1 Sl 1000 0:01 \_ /usr/bin/akonadi_contacts_resource --identifier akonadi_contacts_resource_0
1697 1783 1696 1696 ? -1 Sl 1000 0:01 \_ /usr/bin/akonadi_followupreminder_agent --identifier akonadi_followupreminder_agent
1697 1784 1696 1696 ? -1 Sl 1000 0:01 \_ /usr/bin/akonadi_ical_resource --identifier akonadi_ical_resource_0
1697 1785 1696 1696 ? -1 SNl 1000 0:01 \_ /usr/bin/akonadi_indexing_agent --identifier akonadi_indexing_agent
1697 1786 1696 1696 ? -1 Sl 1000 0:01 \_ /usr/bin/akonadi_maildir_resource --identifier akonadi_maildir_resource_0
1697 1787 1696 1696 ? -1 Sl 1000 0:01 \_ /usr/bin/akonadi_maildispatcher_agent --identifier akonadi_maildispatcher_agent
1697 1788 1696 1696 ? -1 SLl 1000 0:01 \_ /usr/bin/akonadi_mailfilter_agent --identifier akonadi_mailfilter_agent
1697 1797 1696 1696 ? -1 Sl 1000 0:01 \_ /usr/bin/akonadi_migration_agent --identifier akonadi_migration_agent
1697 1798 1696 1696 ? -1 Sl 1000 0:01 \_ /usr/bin/akonadi_newmailnotifier_agent --identifier akonadi_newmailnotifier_agent
1697 1802 1696 1696 ? -1 Sl 1000 0:02 \_ /usr/bin/akonadi_notes_agent --identifier akonadi_notes_agent
1697 1804 1696 1696 ? -1 SLl 1000 0:02 \_ /usr/bin/akonadi_sendlater_agent --identifier akonadi_sendlater_agent
1697 1806 1696 1696 ? -1 SLl 1000 0:02 \_ /usr/bin/akonadi_unifiedmailbox_agent --identifier akonadi_unifiedmailbox_agent
1 1738 1737 1737 ? -1 S 1000 0:00 /usr/bin/xsettingsd
1 2115 1623 1623 ? -1 Sl 1000 0:01 /usr/libexec/at-spi2-registryd --use-gnome-session
1 7918 7917 7917 ? -1 Sl 1000 0:00 /opt/google/chrome/chrome_crashpad_handler --monitor-self --monitor-self-annotation=ptype=crashpad-handler --database=/ho
1 7920 7919 7919 ? -1 Sl 1000 0:00 /opt/google/chrome/chrome_crashpad_handler --no-periodic-tasks --monitor-self-annotation=ptype=crashpad-handler --databas
可以观察到几点：
- PID=1是
/sbin/init，也就是init进程，负责系统的启动关闭； - PID=2是
[kthreadd]，是kernel thread daemon； - plasmashell桌面是由init启动的一个进程，后续启动的GUI的进程都是他的子进程，比如chrome；
- yakuake是由init进程直接启动的，不是由plasmashell启动的。可能是因为它是开机自启动？如果此时手动开启一个konsole，它的父进程应该还是plasmashell吧？如果启动一个kate，应该也是plasmashell的子进程；
- yakuake开了两个tty，启动了一些进程，就是之前我们讨论过的；
- 如果启动一个konsole，应该也是有tty的；
TODO：以上两个关于konsole的猜想需要验证一下。
关于pid=0的进程：
- https://unix.stackexchange.com/questions/83322/which-process-has-pid-0
关于init进程：
- https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/6/html/installation_guide/s2-boot-init-shutdown-init
- https://web.mit.edu/rhel-doc/3/rhel-rg-en-3/s1-boot-init-shutdown-process.html
Ref:
- https://zhuanlan.zhihu.com/p/266720121
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