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ubuntu:proc

Proc

The /proc file system, doesn't contain 'real' files. Most of the 'files' within /proc have a file size of 0.

/proc simply acts as an interface to internal data structures in the kernel. It can be used to obtain information about the system (such as memory, disks mounted, hardware configuration, etc.) and to change certain kernel parameters at runtime (sysctl).

It not only allows access to process data but also allows you to request the kernel status by reading files in the hierarchy.

Process-Specific Sub-directories

The /proc directory contains (among other things) one sub-directory for each process running on the system, which is named after the process ID (PID).

Each process sub-directory has the following entries.

FileContent
clear_refsClears page referenced bits shown in smaps output.
cmdlineCommand line arguments.
cpuCurrent and last cpu in which it was executed (2.4)(smp).
cwdLink to the current working directory.
environValues of environment variables.
exeLink to the executable of this process.
fdDirectory, which contains all file descriptors.
mapsMemory maps to executables and library files (2.4).
memMemory held by this process.
rootLink to the root directory of this process.
statProcess status.
statmProcess memory status information.
statusProcess status in human readable form.
wchanIf CONFIG_KALLSYMS is set, a pre-decoded wchan.
pagemapPage table.
stackReport full stack trace, enable via CONFIG_STACKTRACE.
smapsAn extension based on maps, showing the memory consumption of each mapping.

Kernel data

Similar to the process entries, the kernel data files give information about the running kernel. The files used to obtain this information are contained in /proc and are listed here. Not all of these will be present in your system. It depends on the kernel configuration and the loaded modules, which files are there, and which are missing.

FileContent
apmAdvanced power management info.
buddyinfoKernel memory allocator information (2.5).
busDirectory containing bus specific information.
cmdlineKernel command line.
cpuinfoInfo about the CPU.
devicesAvailable devices (block and character).
dmaUsed DMS channels.
filesystemsSupported filesystems.
driverVarious drivers grouped here, currently rtc (2.4).
execdomainsExecdomains, related to security (2.4).
fbFrame Buffer devices (2.4).
fsFile system parameters, currently nfs/exports (2.4).
ideDirectory containing info about the IDE subsystem.
interruptsInterrupt usage.
iomemMemory map (2.4).
ioportsI/O port usage.
irqMasks for irq to cpu affinity (2.4) (smp?).
isapnpISA PnP (Plug&Play) Info (2.4).
kcoreKernel core image (can be ELF or A.OUT (deprecated in 2.4)).
kmsgKernel messages.
ksymsKernel symbol table.
loadavgLoad average of last 1, 5 & 15 minutes.
locksKernel locks.
meminfoMemory info.
miscMiscellaneous.
modulesList of loaded modules.
mountsMounted filesystems.
netNetworking info.
pagetypeinfoAdditional page allocator information (see text) (2.5).
parportsParallel Ports
partitionsTable of partitions known to the system.
pciDeprecated info of PCI bus (new way → /proc/bus/pci/, decoupled by lspci (2.4).
rtcReal time clock.
scsiSCSI info.
slabinfoSlab pool info.
softirqssoftirq usage.
statOverall statistics.
swapsSwap space utilization.
sysSystem info.
sysvipcInfo of SysVIPC Resources (msg, sem, shm) (2.4).
ttyInfo of tty drivers.
uptimeSystem uptime.
versionKernel version.
videobttv info of video resources (2.4).
vmallocinfoShow vmalloced areas.

Per Process Parameters

Through /proc/<pid>/xxx where xxx is the file from the following table:

FileContent
oom_adjOut of memory killer score. Deprecated and will be removed. Replaced by oom_score_adj.
oom_score_adjOut of memory killer score.
ioIO accounting fields, which are IO statistics for each running process.
coredump_filterCore dump filtering settings.
mountinfoInformation about mounts.
commTask name excluding path.

References

ubuntu/proc.txt · Last modified: 2020/07/15 09:30 by 127.0.0.1

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