Documentation System Daemons Beat

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systemd changes

New unit types

slice units

Slice units are used to group units that manage processes into a hierarchy to allow control of resources allocated for the slice. The default slices, listed below, are automatically populated. + machine.slice, for virtual machines and containers + system.slice, for system services + user.slice, for user sessions

Scope and service units assigned to a slice are descendants of that slice's node in the control group tree. A slice's name describes its position relative to the root slice. The output below demonstrates how "user-1000.slice" is a child of "user.slice" which is in turn a child of the root slice.

user.slice - User and Session Slice

  Loaded: loaded (/usr/lib/systemd/system/user.slice; static)
  Active: active since Sun 2013-09-08 01:23:40 MDT; 18h ago
    Docs: man:systemd.special(7)
  CGroup: /user.slice
          ├─user-1000.slice
          │ ├─session-21.scope
          │ │ ├─9226 sshd: pete [priv]
          │ │ ├─9229 sshd: pete@pts/4
          │ │ ├─9230 -bash
          │ │ ├─9262 sudo su -
          │ │ ├─9270 su -
          │ │ ├─9271 -bash
          │ │ └─9509 screen -R
          │ ├─session-18.scope
          │ │ ├─ 7939 sshd: pete [priv]
          │ │ ├─ 7942 sshd: pete@pts/0
          │ │ ├─ 7943 -bash
          │ │ ├─ 7982 sudo su -
          │ │ ├─ 7988 su -
          │ │ ├─ 7989 -bash
          │ │ ├─ 8206 SCREEN
          │ │ ├─ 8207 /bin/bash
          │ │ ├─ 8237 /bin/bash
          │ │ ├─ 8486 less NEWS
          │ │ ├─ 8489 /bin/bash
          │ │ └─10637 systemctl status user.slice
          <truncated>

Other Systemd Changes

systemd-cryptsetup for TrueCrypt

Support for TrueCrypt volumes in Fedora is expanded by systemd-cryptsetup's support for the technology, allowing easy authentication to TrueCrypt volumes during boot.

systemctl

Filtering by unit state

systemctl now supports filtering the unit list output by load state. The --state option will accept any value or a comma-separated list values of LOAD, SUB, or ACTIVE states. For example:

systemctl --state failed

journalctl

Viewing the logs of a specific boot

journalctl -b can be used to look for boot output of a specific boot. For example:

journalctl -b # output from current boot
journalctl -b -1 #output from previous boot

In addition to relative boot sequence, journalctl assigns a 128bit boot ID that can be referenced. For example,

journalctl -b  38fd9c3303574ed38e822233457f6b77 # output from a specific designated boot

Referencing the journal with 'cursors'

journalctl can reference the contents of the journal by a record identifier known as a 'cursor'. Similar to a git hash, the cursor uniquely identifies a point in the journal.

If you add --show-cursor to a journalctl query, the last line of output will contain the cursor value:

journalctl -b -u network --show-cursor --since 15:00
Sep 08 15:37:59 localhost.localdomain network[4074]: [FAILED]
Sep 08 15:37:59 localhost.localdomain systemd[1]: network.service: control process exited, code=exited status=1
Sep 08 15:37:59 localhost.localdomain systemd[1]: Failed to start LSB: Bring up/down networking.
Sep 08 15:37:59 localhost.localdomain systemd[1]: Unit network.service entered failed state.
-- cursor: s=13497722134642a2ac1544bada0c8836;i=1120d;b=8491c05dabd3444ca122e7069b5de0a9;m=db2118a46;t=4e5e7d81c7402;x=d177768ac95df831

The cursor can be used to identify that point in the journal in a broader query to provide context:

journalctl -c "s=13497722134642a2ac1544bada0c8836;i=1120d;b=8491c05dabd3444ca122e7069b5de0a9;m=db2118a46;t=4e5e7d81c7402;x=d177768ac95df831"

Scripts parsing journalctl's output can store the cursor value and use it on their next run to pick up where they left off:

journalctl --after-cursor "s=13497722134642a2ac1544bada0c8836;i=1120d;b=8491c05dabd3444ca122e7069b5de0a9;m=db2118a46;t=4e5e7d81c7402;x=d177768ac95df831"